Neurology

CINCINNATI – Cerebral palsy affects about 3 in every 1,000 children, but there is usually little sign of the condition at birth. Instead, it usually shows clinical manifestation between ages 2 and 5, and a diagnosis can trigger early interventions that can improve long-term outcomes.

Physicians and patients would benefit from a screening method for cerebral palsy at birth, but that has so far eluded researchers.

At the 2022 annual meeting of the Child Neurology Society, researchers presented evidence that respiratory rate measured in the last 24 hours of residence in the neonate intensive care unit (NICU) predicts later onset of cerebral palsy, with higher variability associated with increased cerebral palsy risk.

The study results were promising, according to Marc Patterson, MD, who comoderated the session. “It gives us more confidence in predicting the children at risk and making sure that they’re going to be followed closely to get the interventions they need to help them,” said Dr. Patterson, who is a professor of neurology, pediatrics, and medical genetics at Mayo Medical School in Rochester, Minn.

“By the time a child is 5 or 6, the symptoms are usually very obvious, but you really want to intervene as soon as possible before their brain’s plasticity decreases over time, so the earlier you can intervene in general, the better your results are going to be,” said Dr. Patterson.

There are tools available to diagnose cerebral palsy at an earlier age, including the Prechtl General Movements Assessment (GMA), which can be done up to 5 months of corrected age. It has 97% sensitivity and 89% specificity for cerebral palsy. The Hammersmith Infant Neurological Examination (HINE), which can be used in the same age range, and has 72-91% sensitivity and 100% specificity.

Both of the available tools are resource intensive and require trained clinicians, and may be unavailable in many areas. Despite these tools, early diagnosis of cerebral palsy is still underemployed, according to Arohi Saxena, a third-year medical student at Washington University in St. Louis, who presented the study results.
 

Respiratory rate variability may indicate increased risk

The researchers set out to identify objective metrics that correlated with HINE and GMA scores. They looked at kinematic data from practical assessments carried out by their physical therapists, as well as vital sign instability obtained at NICU discharge, which was based on suggestions that hemodynamic instability may be linked to later risk of cerebral palsy, according to Ms. Saxena.

They analyzed data from 31 infants with a corrected age of 8-25 weeks at a tertiary NICU follow-up clinic. Of these, 18 displayed fidgety movements on their Prechtl assessment, and 13 did not.

They used DeepLabCut software to analyze data from videos of the Prechtl assessment, with a focus on range and variance of hand and foot movements normalized to nose-to-umbilicus distance. They also analyzed pulse and respiratory data from the final 24 hours before NICU discharge.

They found that infants without fidgety movements had decreased hand and foot movement ranges (P = .04). There was no significant difference between the two groups with respect to pulse measurements. However, the respiratory rate range and variance was significantly higher in infants without fidgety movements. “Infants who are at higher risk for developing cerebral palsy had more respiratory instability early on in life,” said Ms. Saxena during her talk.

When they compared values to HINE scores, they found a correlation with less foot movement and a predisposition to develop cerebral palsy, but no correlation with hand movement. A lower HINE sore also correlated to larger respiratory rate range and variance (P < .01 for both).

“Our hypothesis to explain this link is that respiratory rate variability is likely driven by neonatal injury in the brainstem, where the respiratory centers are located. In some infants, this may correlate with more extensive cerebral injury that could predict the development of cerebral palsy,” said Ms. Saxena.

The group plans to increase its sample size as well as to conduct long-term follow-up on the infants to see how many receive formal diagnoses of cerebral palsy.

After her talk, asked by a moderator why motor assessments were not a reliable predictor in their study, Ms. Saxena pointed to the inexperience of assessors at the institution, where Prechtl testing had only recently begun.

“I think a lot of it is to do with the more subjective nature of the motor assessment. We definitely saw kind of a trend where in the earlier data that was collected, right when our institutions started doing these Prechtls, it was even less of a reliable effect. So I think possibly as clinicians continue to get more familiar with this assessment and there’s more like a validated and robust scoring system, maybe we’ll see a stronger correlation,” she said.

Ms. Saxena had no relevant disclosures. Coauthor Boomah Aravamuthan, MD, DPhil, is a consultant for Neurocrine Biosciences and has received royalties from UpToDate and funding from the National Institute of Neurological Disorders and Stroke.

CINCINNATI – Cerebral palsy affects about 3 in every 1,000 children, but there is usually little sign of the condition at birth. Instead, it usually shows clinical manifestation between ages 2 and 5, and a diagnosis can trigger early interventions that can improve long-term outcomes.

Physicians and patients would benefit from a screening method for cerebral palsy at birth, but that has so far eluded researchers.

At the 2022 annual meeting of the Child Neurology Society, researchers presented evidence that respiratory rate measured in the last 24 hours of residence in the neonate intensive care unit (NICU) predicts later onset of cerebral palsy, with higher variability associated with increased cerebral palsy risk.

The study results were promising, according to Marc Patterson, MD, who comoderated the session. “It gives us more confidence in predicting the children at risk and making sure that they’re going to be followed closely to get the interventions they need to help them,” said Dr. Patterson, who is a professor of neurology, pediatrics, and medical genetics at Mayo Medical School in Rochester, Minn.

“By the time a child is 5 or 6, the symptoms are usually very obvious, but you really want to intervene as soon as possible before their brain’s plasticity decreases over time, so the earlier you can intervene in general, the better your results are going to be,” said Dr. Patterson.

There are tools available to diagnose cerebral palsy at an earlier age, including the Prechtl General Movements Assessment (GMA), which can be done up to 5 months of corrected age. It has 97% sensitivity and 89% specificity for cerebral palsy. The Hammersmith Infant Neurological Examination (HINE), which can be used in the same age range, and has 72-91% sensitivity and 100% specificity.

Both of the available tools are resource intensive and require trained clinicians, and may be unavailable in many areas. Despite these tools, early diagnosis of cerebral palsy is still underemployed, according to Arohi Saxena, a third-year medical student at Washington University in St. Louis, who presented the study results.
 

Respiratory rate variability may indicate increased risk

The researchers set out to identify objective metrics that correlated with HINE and GMA scores. They looked at kinematic data from practical assessments carried out by their physical therapists, as well as vital sign instability obtained at NICU discharge, which was based on suggestions that hemodynamic instability may be linked to later risk of cerebral palsy, according to Ms. Saxena.

They analyzed data from 31 infants with a corrected age of 8-25 weeks at a tertiary NICU follow-up clinic. Of these, 18 displayed fidgety movements on their Prechtl assessment, and 13 did not.

They used DeepLabCut software to analyze data from videos of the Prechtl assessment, with a focus on range and variance of hand and foot movements normalized to nose-to-umbilicus distance. They also analyzed pulse and respiratory data from the final 24 hours before NICU discharge.

They found that infants without fidgety movements had decreased hand and foot movement ranges (P = .04). There was no significant difference between the two groups with respect to pulse measurements. However, the respiratory rate range and variance was significantly higher in infants without fidgety movements. “Infants who are at higher risk for developing cerebral palsy had more respiratory instability early on in life,” said Ms. Saxena during her talk.

When they compared values to HINE scores, they found a correlation with less foot movement and a predisposition to develop cerebral palsy, but no correlation with hand movement. A lower HINE sore also correlated to larger respiratory rate range and variance (P < .01 for both).

“Our hypothesis to explain this link is that respiratory rate variability is likely driven by neonatal injury in the brainstem, where the respiratory centers are located. In some infants, this may correlate with more extensive cerebral injury that could predict the development of cerebral palsy,” said Ms. Saxena.

The group plans to increase its sample size as well as to conduct long-term follow-up on the infants to see how many receive formal diagnoses of cerebral palsy.

After her talk, asked by a moderator why motor assessments were not a reliable predictor in their study, Ms. Saxena pointed to the inexperience of assessors at the institution, where Prechtl testing had only recently begun.

“I think a lot of it is to do with the more subjective nature of the motor assessment. We definitely saw kind of a trend where in the earlier data that was collected, right when our institutions started doing these Prechtls, it was even less of a reliable effect. So I think possibly as clinicians continue to get more familiar with this assessment and there’s more like a validated and robust scoring system, maybe we’ll see a stronger correlation,” she said.

Ms. Saxena had no relevant disclosures. Coauthor Boomah Aravamuthan, MD, DPhil, is a consultant for Neurocrine Biosciences and has received royalties from UpToDate and funding from the National Institute of Neurological Disorders and Stroke.

CINCINNATI – Cerebral palsy affects about 3 in every 1,000 children, but there is usually little sign of the condition at birth. Instead, it usually shows clinical manifestation between ages 2 and 5, and a diagnosis can trigger early interventions that can improve long-term outcomes.

Physicians and patients would benefit from a screening method for cerebral palsy at birth, but that has so far eluded researchers.

At the 2022 annual meeting of the Child Neurology Society, researchers presented evidence that respiratory rate measured in the last 24 hours of residence in the neonate intensive care unit (NICU) predicts later onset of cerebral palsy, with higher variability associated with increased cerebral palsy risk.

The study results were promising, according to Marc Patterson, MD, who comoderated the session. “It gives us more confidence in predicting the children at risk and making sure that they’re going to be followed closely to get the interventions they need to help them,” said Dr. Patterson, who is a professor of neurology, pediatrics, and medical genetics at Mayo Medical School in Rochester, Minn.

“By the time a child is 5 or 6, the symptoms are usually very obvious, but you really want to intervene as soon as possible before their brain’s plasticity decreases over time, so the earlier you can intervene in general, the better your results are going to be,” said Dr. Patterson.

There are tools available to diagnose cerebral palsy at an earlier age, including the Prechtl General Movements Assessment (GMA), which can be done up to 5 months of corrected age. It has 97% sensitivity and 89% specificity for cerebral palsy. The Hammersmith Infant Neurological Examination (HINE), which can be used in the same age range, and has 72-91% sensitivity and 100% specificity.

Both of the available tools are resource intensive and require trained clinicians, and may be unavailable in many areas. Despite these tools, early diagnosis of cerebral palsy is still underemployed, according to Arohi Saxena, a third-year medical student at Washington University in St. Louis, who presented the study results.
 

Respiratory rate variability may indicate increased risk

The researchers set out to identify objective metrics that correlated with HINE and GMA scores. They looked at kinematic data from practical assessments carried out by their physical therapists, as well as vital sign instability obtained at NICU discharge, which was based on suggestions that hemodynamic instability may be linked to later risk of cerebral palsy, according to Ms. Saxena.

They analyzed data from 31 infants with a corrected age of 8-25 weeks at a tertiary NICU follow-up clinic. Of these, 18 displayed fidgety movements on their Prechtl assessment, and 13 did not.

They used DeepLabCut software to analyze data from videos of the Prechtl assessment, with a focus on range and variance of hand and foot movements normalized to nose-to-umbilicus distance. They also analyzed pulse and respiratory data from the final 24 hours before NICU discharge.

They found that infants without fidgety movements had decreased hand and foot movement ranges (P = .04). There was no significant difference between the two groups with respect to pulse measurements. However, the respiratory rate range and variance was significantly higher in infants without fidgety movements. “Infants who are at higher risk for developing cerebral palsy had more respiratory instability early on in life,” said Ms. Saxena during her talk.

When they compared values to HINE scores, they found a correlation with less foot movement and a predisposition to develop cerebral palsy, but no correlation with hand movement. A lower HINE sore also correlated to larger respiratory rate range and variance (P < .01 for both).

“Our hypothesis to explain this link is that respiratory rate variability is likely driven by neonatal injury in the brainstem, where the respiratory centers are located. In some infants, this may correlate with more extensive cerebral injury that could predict the development of cerebral palsy,” said Ms. Saxena.

The group plans to increase its sample size as well as to conduct long-term follow-up on the infants to see how many receive formal diagnoses of cerebral palsy.

After her talk, asked by a moderator why motor assessments were not a reliable predictor in their study, Ms. Saxena pointed to the inexperience of assessors at the institution, where Prechtl testing had only recently begun.

“I think a lot of it is to do with the more subjective nature of the motor assessment. We definitely saw kind of a trend where in the earlier data that was collected, right when our institutions started doing these Prechtls, it was even less of a reliable effect. So I think possibly as clinicians continue to get more familiar with this assessment and there’s more like a validated and robust scoring system, maybe we’ll see a stronger correlation,” she said.

Ms. Saxena had no relevant disclosures. Coauthor Boomah Aravamuthan, MD, DPhil, is a consultant for Neurocrine Biosciences and has received royalties from UpToDate and funding from the National Institute of Neurological Disorders and Stroke.

Apixaban offers greater protection than rivaroxaban against ischemic stroke, systemic embolism, and bleeding in patients with both atrial fibrillation (AFib) and valvular heart disease (VHD), a new study finds.

Compared with rivaroxaban, apixaban cut risks nearly in half, suggesting that clinicians should consider these new data when choosing an anticoagulant, reported lead author Ghadeer K. Dawwas, PhD, of the University of Pennsylvania, Philadelphia, and colleagues.

In the new retrospective study involving almost 20,000 patients, Dr. Dawwas and her colleagues “emulated a target trial” using private insurance claims from Optum’s deidentified Clinformatics Data Mart Database. The cohort was narrowed from a screened population of 58,210 patients with concurrent AFib and VHD to 9,947 new apixaban users who could be closely matched with 9,947 new rivaroxaban users. Covariates included provider specialty, type of VHD, demographic characteristics, measures of health care use, baseline use of medications, and baseline comorbidities.

The primary effectiveness outcome was a composite of systemic embolism and ischemic stroke, while the primary safety outcome was a composite of intracranial or gastrointestinal bleeding.

“Although several ongoing trials aim to compare apixaban with warfarin in patients with AFib and VHD, none of these trials will directly compare apixaban and rivaroxaban,” the investigators wrote. Their report is in Annals of Internal Medicine.

Dr. Dawwas and colleagues previously showed that direct oral anticoagulants (DOACs) were safer and more effective than warfarin in the same patient population. Comparing apixaban and rivaroxaban – the two most common DOACs – was the next logical step, Dr. Dawwas said in an interview.
 

Study results

Compared with rivaroxaban, patients who received apixaban had a 43% reduced risk of stroke or embolism (hazard ratio [HR], 0.57; 95% confidence interval [CI], 0.40-0.80). Apixaban’s ability to protect against bleeding appeared even more pronounced, with a 49% reduced risk over rivaroxaban (HR, 0.51; 95% CI, 0.41-0.62).

Comparing the two agents on an absolute basis, apixaban reduced risk of embolism or stroke by 0.2% within the first 6 months of treatment initiation, and 1.1% within the first year of initiation. At the same time points, absolute risk reductions for bleeding were 1.2% and 1.9%, respectively.

The investigators noted that their results held consistent in an alternative analysis that considered separate types of VHD.

“Based on the results from our analysis, we showed that apixaban is effective and safe in patients with atrial fibrillation and valvular heart diseases,” Dr. Dawwas said.
 

Head-to-head trial needed to change practice

Christopher M. Bianco, DO, associate professor of medicine at West Virginia University Heart and Vascular Institute, Morgantown, said the findings “add to the growing body of literature,” but “a head-to-head trial would be necessary to make a definitive change to clinical practice.”

Dr. Bianco, who recently conducted a retrospective analysis of apixaban and rivaroxaban that found no difference in safety and efficacy among a different patient population, said these kinds of studies are helpful in generating hypotheses, but they can’t account for all relevant clinical factors.

“There are just so many things that go into the decision-making process of [prescribing] apixaban and rivaroxaban,” he said. “Even though [Dr. Dawwas and colleagues] used propensity matching, you’re never going to be able to sort that out with a retrospective analysis.”

Specifically, Dr. Bianco noted that the findings did not include dose data. This is a key gap, he said, considering how often real-world datasets have shown that providers underdose DOACs for a number of unaccountable reasons, and how frequently patients exhibit poor adherence.

The study also lacked detail concerning the degree of renal dysfunction, which can determine drug eligibility, Dr. Bianco said. Furthermore, attempts to stratify patients based on thrombosis and bleeding risk were likely “insufficient,” he added.

Dr. Bianco also cautioned that the investigators defined valvular heart disease as any valve-related disease of any severity. In contrast, previous studies have generally restricted valvular heart disease to patients with mitral stenosis or prosthetic valves.

“This is definitely not the traditional definition of valvular heart disease, so the title is a little bit misleading in that sense, although they certainly do disclose that in the methods,” Dr. Bianco said.

On a more positive note, he highlighted the size of the patient population, and the real-world data, which included many patients who would be excluded from clinical trials.

More broadly, the study helps drive research forward, Dr. Bianco concluded; namely, by attracting financial support for a more powerful head-to-head trial that drug makers are unlikely to fund due to inherent market risk.

This study was supported by the National Institutes of Health. The investigators disclosed additional relationships with Takeda, Spark, Sanofi, and others. Dr. Bianco disclosed no conflicts of interest.

Apixaban offers greater protection than rivaroxaban against ischemic stroke, systemic embolism, and bleeding in patients with both atrial fibrillation (AFib) and valvular heart disease (VHD), a new study finds.

Compared with rivaroxaban, apixaban cut risks nearly in half, suggesting that clinicians should consider these new data when choosing an anticoagulant, reported lead author Ghadeer K. Dawwas, PhD, of the University of Pennsylvania, Philadelphia, and colleagues.

In the new retrospective study involving almost 20,000 patients, Dr. Dawwas and her colleagues “emulated a target trial” using private insurance claims from Optum’s deidentified Clinformatics Data Mart Database. The cohort was narrowed from a screened population of 58,210 patients with concurrent AFib and VHD to 9,947 new apixaban users who could be closely matched with 9,947 new rivaroxaban users. Covariates included provider specialty, type of VHD, demographic characteristics, measures of health care use, baseline use of medications, and baseline comorbidities.

The primary effectiveness outcome was a composite of systemic embolism and ischemic stroke, while the primary safety outcome was a composite of intracranial or gastrointestinal bleeding.

“Although several ongoing trials aim to compare apixaban with warfarin in patients with AFib and VHD, none of these trials will directly compare apixaban and rivaroxaban,” the investigators wrote. Their report is in Annals of Internal Medicine.

Dr. Dawwas and colleagues previously showed that direct oral anticoagulants (DOACs) were safer and more effective than warfarin in the same patient population. Comparing apixaban and rivaroxaban – the two most common DOACs – was the next logical step, Dr. Dawwas said in an interview.
 

Study results

Compared with rivaroxaban, patients who received apixaban had a 43% reduced risk of stroke or embolism (hazard ratio [HR], 0.57; 95% confidence interval [CI], 0.40-0.80). Apixaban’s ability to protect against bleeding appeared even more pronounced, with a 49% reduced risk over rivaroxaban (HR, 0.51; 95% CI, 0.41-0.62).

Comparing the two agents on an absolute basis, apixaban reduced risk of embolism or stroke by 0.2% within the first 6 months of treatment initiation, and 1.1% within the first year of initiation. At the same time points, absolute risk reductions for bleeding were 1.2% and 1.9%, respectively.

The investigators noted that their results held consistent in an alternative analysis that considered separate types of VHD.

“Based on the results from our analysis, we showed that apixaban is effective and safe in patients with atrial fibrillation and valvular heart diseases,” Dr. Dawwas said.
 

Head-to-head trial needed to change practice

Christopher M. Bianco, DO, associate professor of medicine at West Virginia University Heart and Vascular Institute, Morgantown, said the findings “add to the growing body of literature,” but “a head-to-head trial would be necessary to make a definitive change to clinical practice.”

Dr. Bianco, who recently conducted a retrospective analysis of apixaban and rivaroxaban that found no difference in safety and efficacy among a different patient population, said these kinds of studies are helpful in generating hypotheses, but they can’t account for all relevant clinical factors.

“There are just so many things that go into the decision-making process of [prescribing] apixaban and rivaroxaban,” he said. “Even though [Dr. Dawwas and colleagues] used propensity matching, you’re never going to be able to sort that out with a retrospective analysis.”

Specifically, Dr. Bianco noted that the findings did not include dose data. This is a key gap, he said, considering how often real-world datasets have shown that providers underdose DOACs for a number of unaccountable reasons, and how frequently patients exhibit poor adherence.

The study also lacked detail concerning the degree of renal dysfunction, which can determine drug eligibility, Dr. Bianco said. Furthermore, attempts to stratify patients based on thrombosis and bleeding risk were likely “insufficient,” he added.

Dr. Bianco also cautioned that the investigators defined valvular heart disease as any valve-related disease of any severity. In contrast, previous studies have generally restricted valvular heart disease to patients with mitral stenosis or prosthetic valves.

“This is definitely not the traditional definition of valvular heart disease, so the title is a little bit misleading in that sense, although they certainly do disclose that in the methods,” Dr. Bianco said.

On a more positive note, he highlighted the size of the patient population, and the real-world data, which included many patients who would be excluded from clinical trials.

More broadly, the study helps drive research forward, Dr. Bianco concluded; namely, by attracting financial support for a more powerful head-to-head trial that drug makers are unlikely to fund due to inherent market risk.

This study was supported by the National Institutes of Health. The investigators disclosed additional relationships with Takeda, Spark, Sanofi, and others. Dr. Bianco disclosed no conflicts of interest.

Apixaban offers greater protection than rivaroxaban against ischemic stroke, systemic embolism, and bleeding in patients with both atrial fibrillation (AFib) and valvular heart disease (VHD), a new study finds.

Compared with rivaroxaban, apixaban cut risks nearly in half, suggesting that clinicians should consider these new data when choosing an anticoagulant, reported lead author Ghadeer K. Dawwas, PhD, of the University of Pennsylvania, Philadelphia, and colleagues.

In the new retrospective study involving almost 20,000 patients, Dr. Dawwas and her colleagues “emulated a target trial” using private insurance claims from Optum’s deidentified Clinformatics Data Mart Database. The cohort was narrowed from a screened population of 58,210 patients with concurrent AFib and VHD to 9,947 new apixaban users who could be closely matched with 9,947 new rivaroxaban users. Covariates included provider specialty, type of VHD, demographic characteristics, measures of health care use, baseline use of medications, and baseline comorbidities.

The primary effectiveness outcome was a composite of systemic embolism and ischemic stroke, while the primary safety outcome was a composite of intracranial or gastrointestinal bleeding.

“Although several ongoing trials aim to compare apixaban with warfarin in patients with AFib and VHD, none of these trials will directly compare apixaban and rivaroxaban,” the investigators wrote. Their report is in Annals of Internal Medicine.

Dr. Dawwas and colleagues previously showed that direct oral anticoagulants (DOACs) were safer and more effective than warfarin in the same patient population. Comparing apixaban and rivaroxaban – the two most common DOACs – was the next logical step, Dr. Dawwas said in an interview.
 

Study results

Compared with rivaroxaban, patients who received apixaban had a 43% reduced risk of stroke or embolism (hazard ratio [HR], 0.57; 95% confidence interval [CI], 0.40-0.80). Apixaban’s ability to protect against bleeding appeared even more pronounced, with a 49% reduced risk over rivaroxaban (HR, 0.51; 95% CI, 0.41-0.62).

Comparing the two agents on an absolute basis, apixaban reduced risk of embolism or stroke by 0.2% within the first 6 months of treatment initiation, and 1.1% within the first year of initiation. At the same time points, absolute risk reductions for bleeding were 1.2% and 1.9%, respectively.

The investigators noted that their results held consistent in an alternative analysis that considered separate types of VHD.

“Based on the results from our analysis, we showed that apixaban is effective and safe in patients with atrial fibrillation and valvular heart diseases,” Dr. Dawwas said.
 

Head-to-head trial needed to change practice

Christopher M. Bianco, DO, associate professor of medicine at West Virginia University Heart and Vascular Institute, Morgantown, said the findings “add to the growing body of literature,” but “a head-to-head trial would be necessary to make a definitive change to clinical practice.”

Dr. Bianco, who recently conducted a retrospective analysis of apixaban and rivaroxaban that found no difference in safety and efficacy among a different patient population, said these kinds of studies are helpful in generating hypotheses, but they can’t account for all relevant clinical factors.

“There are just so many things that go into the decision-making process of [prescribing] apixaban and rivaroxaban,” he said. “Even though [Dr. Dawwas and colleagues] used propensity matching, you’re never going to be able to sort that out with a retrospective analysis.”

Specifically, Dr. Bianco noted that the findings did not include dose data. This is a key gap, he said, considering how often real-world datasets have shown that providers underdose DOACs for a number of unaccountable reasons, and how frequently patients exhibit poor adherence.

The study also lacked detail concerning the degree of renal dysfunction, which can determine drug eligibility, Dr. Bianco said. Furthermore, attempts to stratify patients based on thrombosis and bleeding risk were likely “insufficient,” he added.

Dr. Bianco also cautioned that the investigators defined valvular heart disease as any valve-related disease of any severity. In contrast, previous studies have generally restricted valvular heart disease to patients with mitral stenosis or prosthetic valves.

“This is definitely not the traditional definition of valvular heart disease, so the title is a little bit misleading in that sense, although they certainly do disclose that in the methods,” Dr. Bianco said.

On a more positive note, he highlighted the size of the patient population, and the real-world data, which included many patients who would be excluded from clinical trials.

More broadly, the study helps drive research forward, Dr. Bianco concluded; namely, by attracting financial support for a more powerful head-to-head trial that drug makers are unlikely to fund due to inherent market risk.

This study was supported by the National Institutes of Health. The investigators disclosed additional relationships with Takeda, Spark, Sanofi, and others. Dr. Bianco disclosed no conflicts of interest.

Martha Welch, MD, spent the better part of three decades in private practice treating children with emotional, behavioral, and developmental disorders before accepting a job on the faculty of Columbia University, New York, in 1997.

She took the position, she said, with a mission: to find evidence to support what she’d observed in her practice – that parents could, by making stronger emotional connections, change the trajectory of development for preemie infants.

With that understanding, Dr. Welch created Family Nurture Intervention (FNI), which has been shown to improve the development of premature babies.

“We saw that no matter what happened to the baby, no matter how avoidant the baby might be, we’re able to overcome this with emotional expression,” Dr. Welch said.

Over the course of the intervention, families work with a specialist who helps bring mother and baby together – both physically and emotionally – until both are calm, which can initially take several hours and over time, minutes.

FNI appears to help families – especially mothers – re-establish an emotional connection often interrupted by their babies’ stressful and uncertain stay in a neonatal intensive care unit (NICU). In turn, both the infant and maternal nervous systems become better regulated, according to researchers.
 

Early challenges

Babies born preterm can face a range of short-term and long-term challenges, such as breathing problems due to an underdeveloped respiratory system, an increased risk of infection from an underdeveloped immune system, and learning difficulties, according to the Mayo Clinic.

Many aspects of FNI are not new: The neonatal intensive care unit has long incorporated activities such as scent cloth exchanges, talking to the baby, and skin-to-skin contact. But the approach Dr. Welch and her colleagues advocate emphasizes building a bond between the mother and the infant.

Mounting evidence shows that FNI can improve a wide range of outcomes for premature babies. In a 2021 study, for example, Dr. Welch’s group showed that FNI was associated with lower heart rates among preemies in the NICU. A 2016 study linked the intervention to reduced depression and anxiety symptoms in mothers of preterm infants. And a 2015 randomized controlled trial showed FNI improved development and behavioral outcomes in infants up to 18 months.

A new study published in Science Translational Medicine showed that the intervention led to a greater likelihood that babies had improved cognitive development later on, narrowing the developmental gap between healthy, full-term babies.

Dr. Welch and her colleagues tested to see if FNI measurably changed brain development in preterm infants who were born at 26-34 weeks of a pregnancy.

“We were blown away by the strength of the effect,” said Pauliina Yrjölä, MSc, a doctoral student and medical physicist at the University of Helsinki, who led the study on which Dr. Welch is a co-author.

Mothers in the intervention group made as much eye contact with the infants as possible and spoke with infants about their feelings.

Intimate sensory interactions between mothers and infants physically altered infants’ cortical networks in the brain and was later correlated to improved neurocognitive performance, according to the researchers.

“I was convinced there were physiological changes; I knew that from my clinical work,” Dr. Welch said. “I wanted to show it in this concrete, scientific way.”
 

Preterm babies face many hurdles

“If we can prevent problems in brain network organization to the extent that’s shown in this study and improve their outcomes, this is worth millions of dollars in terms of cost to society, schooling, health care, especially education, and families,” said Ruth Grunau, PhD, a professor in the Division of Neonatology in the department of pediatrics at the University of British Columbia, Vancouver, who was not involved with the most recent study but has worked with Dr. Welch previously.

Babies born too early, especially before 32 weeks, have higher rates of death and disability, according to the Centers for Disease Control and Prevention.

And preterm babies overall may experience breathing problems and feeding difficulties almost immediately following birth. They may also experience long-term problems such as developmental delays, vision problems, and hearing problems.

Dr. Grunau said that while many other programs and interventions have been used in the neonatal intensive care unit to help infants and mothers, the results from FNI stand out.

Ms. Yrjölä said she was surprised by the strength of the correlation as the infants continued to develop. The infants receiving the Family Nurture Intervention showed brain development close to the control group, which was infants born at full-term.

“Emotional connection is a state, not a trait – and a state can be changed,” said Dr. Welch. “And in this case, it can be changed by the parent through emotional expression.”
 

Steps clinicians can take

Dr. Welch said the approach is highly scalable, and two NICUs that participated in the FNI studies have implemented the program as standard care.

The approach is also gaining interest outside of the clinical setting, as preschool partners have expressed interest in implementing some of the methods to promote development.

Parents, family members, and teachers can use many of the FNI techniques – such as eye contact and emotional expression – to continue to develop and strengthen connection.

For clinicians who want to implement parts of the intervention on their own, Dr. Welch said doctors can observe if the baby looks at or turns toward their mother.

Clinicians can encourage mothers to express deep, emotional feelings toward the infant. Dr. Welch stressed that feelings don’t have to be positive, as many mothers with babies in the NICU have a hard time expressing positive emotions. Crying or talking about the difficulties of their childbirth experience count as expressing emotion. The important part is that the baby hears emotion, of any kind, in the mother’s voice, Dr. Welch said.

As the connection develops, it will eventually take less time for the mother and the baby to form a bond, and eventually the pair will become autonomically regulated.

“This is what gives us hope,” she said. “We affect each other in our autonomic nervous systems. It’s why this treatment works.”

The study was funded by the Finnish Pediatric Foundation, The Finnish Academy, the Juselius Foundation, Aivosäätiö, Neuroscience Center at University of Helsinki and Helsinki University Central Hospital, gifts from the Einhorn Family Charitable Trust, the Fleur Fairman Family, M. D. Stephenson, and The National Health and Medical Research Council of Australia. The authors have disclosed no relevant financial relationships.

A version of this article first appeared on Medscape.com.

Martha Welch, MD, spent the better part of three decades in private practice treating children with emotional, behavioral, and developmental disorders before accepting a job on the faculty of Columbia University, New York, in 1997.

She took the position, she said, with a mission: to find evidence to support what she’d observed in her practice – that parents could, by making stronger emotional connections, change the trajectory of development for preemie infants.

With that understanding, Dr. Welch created Family Nurture Intervention (FNI), which has been shown to improve the development of premature babies.

“We saw that no matter what happened to the baby, no matter how avoidant the baby might be, we’re able to overcome this with emotional expression,” Dr. Welch said.

Over the course of the intervention, families work with a specialist who helps bring mother and baby together – both physically and emotionally – until both are calm, which can initially take several hours and over time, minutes.

FNI appears to help families – especially mothers – re-establish an emotional connection often interrupted by their babies’ stressful and uncertain stay in a neonatal intensive care unit (NICU). In turn, both the infant and maternal nervous systems become better regulated, according to researchers.
 

Early challenges

Babies born preterm can face a range of short-term and long-term challenges, such as breathing problems due to an underdeveloped respiratory system, an increased risk of infection from an underdeveloped immune system, and learning difficulties, according to the Mayo Clinic.

Many aspects of FNI are not new: The neonatal intensive care unit has long incorporated activities such as scent cloth exchanges, talking to the baby, and skin-to-skin contact. But the approach Dr. Welch and her colleagues advocate emphasizes building a bond between the mother and the infant.

Mounting evidence shows that FNI can improve a wide range of outcomes for premature babies. In a 2021 study, for example, Dr. Welch’s group showed that FNI was associated with lower heart rates among preemies in the NICU. A 2016 study linked the intervention to reduced depression and anxiety symptoms in mothers of preterm infants. And a 2015 randomized controlled trial showed FNI improved development and behavioral outcomes in infants up to 18 months.

A new study published in Science Translational Medicine showed that the intervention led to a greater likelihood that babies had improved cognitive development later on, narrowing the developmental gap between healthy, full-term babies.

Dr. Welch and her colleagues tested to see if FNI measurably changed brain development in preterm infants who were born at 26-34 weeks of a pregnancy.

“We were blown away by the strength of the effect,” said Pauliina Yrjölä, MSc, a doctoral student and medical physicist at the University of Helsinki, who led the study on which Dr. Welch is a co-author.

Mothers in the intervention group made as much eye contact with the infants as possible and spoke with infants about their feelings.

Intimate sensory interactions between mothers and infants physically altered infants’ cortical networks in the brain and was later correlated to improved neurocognitive performance, according to the researchers.

“I was convinced there were physiological changes; I knew that from my clinical work,” Dr. Welch said. “I wanted to show it in this concrete, scientific way.”
 

Preterm babies face many hurdles

“If we can prevent problems in brain network organization to the extent that’s shown in this study and improve their outcomes, this is worth millions of dollars in terms of cost to society, schooling, health care, especially education, and families,” said Ruth Grunau, PhD, a professor in the Division of Neonatology in the department of pediatrics at the University of British Columbia, Vancouver, who was not involved with the most recent study but has worked with Dr. Welch previously.

Babies born too early, especially before 32 weeks, have higher rates of death and disability, according to the Centers for Disease Control and Prevention.

And preterm babies overall may experience breathing problems and feeding difficulties almost immediately following birth. They may also experience long-term problems such as developmental delays, vision problems, and hearing problems.

Dr. Grunau said that while many other programs and interventions have been used in the neonatal intensive care unit to help infants and mothers, the results from FNI stand out.

Ms. Yrjölä said she was surprised by the strength of the correlation as the infants continued to develop. The infants receiving the Family Nurture Intervention showed brain development close to the control group, which was infants born at full-term.

“Emotional connection is a state, not a trait – and a state can be changed,” said Dr. Welch. “And in this case, it can be changed by the parent through emotional expression.”
 

Steps clinicians can take

Dr. Welch said the approach is highly scalable, and two NICUs that participated in the FNI studies have implemented the program as standard care.

The approach is also gaining interest outside of the clinical setting, as preschool partners have expressed interest in implementing some of the methods to promote development.

Parents, family members, and teachers can use many of the FNI techniques – such as eye contact and emotional expression – to continue to develop and strengthen connection.

For clinicians who want to implement parts of the intervention on their own, Dr. Welch said doctors can observe if the baby looks at or turns toward their mother.

Clinicians can encourage mothers to express deep, emotional feelings toward the infant. Dr. Welch stressed that feelings don’t have to be positive, as many mothers with babies in the NICU have a hard time expressing positive emotions. Crying or talking about the difficulties of their childbirth experience count as expressing emotion. The important part is that the baby hears emotion, of any kind, in the mother’s voice, Dr. Welch said.

As the connection develops, it will eventually take less time for the mother and the baby to form a bond, and eventually the pair will become autonomically regulated.

“This is what gives us hope,” she said. “We affect each other in our autonomic nervous systems. It’s why this treatment works.”

The study was funded by the Finnish Pediatric Foundation, The Finnish Academy, the Juselius Foundation, Aivosäätiö, Neuroscience Center at University of Helsinki and Helsinki University Central Hospital, gifts from the Einhorn Family Charitable Trust, the Fleur Fairman Family, M. D. Stephenson, and The National Health and Medical Research Council of Australia. The authors have disclosed no relevant financial relationships.

A version of this article first appeared on Medscape.com.

Martha Welch, MD, spent the better part of three decades in private practice treating children with emotional, behavioral, and developmental disorders before accepting a job on the faculty of Columbia University, New York, in 1997.

She took the position, she said, with a mission: to find evidence to support what she’d observed in her practice – that parents could, by making stronger emotional connections, change the trajectory of development for preemie infants.

With that understanding, Dr. Welch created Family Nurture Intervention (FNI), which has been shown to improve the development of premature babies.

“We saw that no matter what happened to the baby, no matter how avoidant the baby might be, we’re able to overcome this with emotional expression,” Dr. Welch said.

Over the course of the intervention, families work with a specialist who helps bring mother and baby together – both physically and emotionally – until both are calm, which can initially take several hours and over time, minutes.

FNI appears to help families – especially mothers – re-establish an emotional connection often interrupted by their babies’ stressful and uncertain stay in a neonatal intensive care unit (NICU). In turn, both the infant and maternal nervous systems become better regulated, according to researchers.
 

Early challenges

Babies born preterm can face a range of short-term and long-term challenges, such as breathing problems due to an underdeveloped respiratory system, an increased risk of infection from an underdeveloped immune system, and learning difficulties, according to the Mayo Clinic.

Many aspects of FNI are not new: The neonatal intensive care unit has long incorporated activities such as scent cloth exchanges, talking to the baby, and skin-to-skin contact. But the approach Dr. Welch and her colleagues advocate emphasizes building a bond between the mother and the infant.

Mounting evidence shows that FNI can improve a wide range of outcomes for premature babies. In a 2021 study, for example, Dr. Welch’s group showed that FNI was associated with lower heart rates among preemies in the NICU. A 2016 study linked the intervention to reduced depression and anxiety symptoms in mothers of preterm infants. And a 2015 randomized controlled trial showed FNI improved development and behavioral outcomes in infants up to 18 months.

A new study published in Science Translational Medicine showed that the intervention led to a greater likelihood that babies had improved cognitive development later on, narrowing the developmental gap between healthy, full-term babies.

Dr. Welch and her colleagues tested to see if FNI measurably changed brain development in preterm infants who were born at 26-34 weeks of a pregnancy.

“We were blown away by the strength of the effect,” said Pauliina Yrjölä, MSc, a doctoral student and medical physicist at the University of Helsinki, who led the study on which Dr. Welch is a co-author.

Mothers in the intervention group made as much eye contact with the infants as possible and spoke with infants about their feelings.

Intimate sensory interactions between mothers and infants physically altered infants’ cortical networks in the brain and was later correlated to improved neurocognitive performance, according to the researchers.

“I was convinced there were physiological changes; I knew that from my clinical work,” Dr. Welch said. “I wanted to show it in this concrete, scientific way.”
 

Preterm babies face many hurdles

“If we can prevent problems in brain network organization to the extent that’s shown in this study and improve their outcomes, this is worth millions of dollars in terms of cost to society, schooling, health care, especially education, and families,” said Ruth Grunau, PhD, a professor in the Division of Neonatology in the department of pediatrics at the University of British Columbia, Vancouver, who was not involved with the most recent study but has worked with Dr. Welch previously.

Babies born too early, especially before 32 weeks, have higher rates of death and disability, according to the Centers for Disease Control and Prevention.

And preterm babies overall may experience breathing problems and feeding difficulties almost immediately following birth. They may also experience long-term problems such as developmental delays, vision problems, and hearing problems.

Dr. Grunau said that while many other programs and interventions have been used in the neonatal intensive care unit to help infants and mothers, the results from FNI stand out.

Ms. Yrjölä said she was surprised by the strength of the correlation as the infants continued to develop. The infants receiving the Family Nurture Intervention showed brain development close to the control group, which was infants born at full-term.

“Emotional connection is a state, not a trait – and a state can be changed,” said Dr. Welch. “And in this case, it can be changed by the parent through emotional expression.”
 

Steps clinicians can take

Dr. Welch said the approach is highly scalable, and two NICUs that participated in the FNI studies have implemented the program as standard care.

The approach is also gaining interest outside of the clinical setting, as preschool partners have expressed interest in implementing some of the methods to promote development.

Parents, family members, and teachers can use many of the FNI techniques – such as eye contact and emotional expression – to continue to develop and strengthen connection.

For clinicians who want to implement parts of the intervention on their own, Dr. Welch said doctors can observe if the baby looks at or turns toward their mother.

Clinicians can encourage mothers to express deep, emotional feelings toward the infant. Dr. Welch stressed that feelings don’t have to be positive, as many mothers with babies in the NICU have a hard time expressing positive emotions. Crying or talking about the difficulties of their childbirth experience count as expressing emotion. The important part is that the baby hears emotion, of any kind, in the mother’s voice, Dr. Welch said.

As the connection develops, it will eventually take less time for the mother and the baby to form a bond, and eventually the pair will become autonomically regulated.

“This is what gives us hope,” she said. “We affect each other in our autonomic nervous systems. It’s why this treatment works.”

The study was funded by the Finnish Pediatric Foundation, The Finnish Academy, the Juselius Foundation, Aivosäätiö, Neuroscience Center at University of Helsinki and Helsinki University Central Hospital, gifts from the Einhorn Family Charitable Trust, the Fleur Fairman Family, M. D. Stephenson, and The National Health and Medical Research Council of Australia. The authors have disclosed no relevant financial relationships.

A version of this article first appeared on Medscape.com.

Contrary to some prior studies, new research suggests that a healthy diet, including the Mediterranean diet, does not reduce dementia risk.

After adjusting for relevant demographic and other lifestyle measures, there was no association between adherence to healthy dietary advice or the Mediterranean diet on the future risk of dementia or amyloid-beta (Abeta) accumulation.

OksanaKiian/Getty Images

“While our study does not rule out a possible association between diet and dementia, we did not find a link in our study, which had a long follow-up period, included younger participants than some other studies and did not require people to remember what foods they had eaten regularly years before,” study investigator Isabelle Glans, MD, of Lund (Sweden) University, said in a news release.

The findings were published online in Neurology.
 

No risk reduction

Several studies have investigated how dietary habits affect dementia risk, with inconsistent results.

The new findings are based on 28,025 adults (61% women; mean age, 58 years at baseline) who were free of dementia at baseline and were followed over a 20-year period as part of the Swedish Malmö Diet and Cancer Study. Dietary habits were assessed with a 7-day food diary, detailed food frequency questionnaire, and in-person interview.

During follow-up, 1,943 individuals (6.9%) developed dementia.

Compared with those who did not develop dementia, those who did develop dementia during follow-up were older and had a lower level of education and more cardiovascular risk factors and comorbidities at baseline.

Individuals who adhered to conventional healthy dietary recommendations did not have a lower risk of developing all-cause dementia (hazard ratio comparing worst with best adherence, 0.93; 95% confidence interval, 0.81-1.08), Alzheimer’s disease (HR, 1.03; 95% CI, 0.85-1.23) or vascular dementia (HR, 0.93; 95% CI, 0.69-1.26).

Adherence to the modified Mediterranean diet also did not appear to lower the risk of all-cause dementia (HR, 0.93; 95% CI, 0.75-1.15), Alzheimer’s disease (HR, 0.90; 95% CI, 0.68-1.19), or vascular dementia (HR, 1.00; 95% CI, 0.65-1.55).

There was also no significant association between diet and Alzheimer’s disease–related pathology, as measured by cerebrospinal fluid analysis of Abeta42 in a subgroup of 738 participants. Various sensitivity analyses yielded similar results.
 

Diet still matters

The authors of an accompanying editorial noted that diet as a “singular factor may not have a strong enough effect on cognition, but is more likely to be considered as one factor embedded with various others, the sum of which may influence the course of cognitive function (diet, regular exercise, vascular risk factor control, avoiding cigarette smoking, drinking alcohol in moderation, etc).

“Diet should not be forgotten and it still matters” but should be regarded as “one part of a multidomain intervention with respect to cognitive performance,” wrote Nils Peters, MD, with the University of Basel (Switzerland), and Benedetta Nacmias, PhD, with the University of Florence (Italy)).

“Key questions that remain include how to provide evidence for promoting the implications of dietary habits on cognition? Overall, dietary strategies will most likely be implicated either in order to reduce the increasing number of older subjects with dementia, or to extend healthy life expectancy, or both,” Dr. Peters and Dr. Nacmias said.

The study had no commercial funding. Dr. Glans, Dr. Peters, and Dr. Nacmias disclosed no relevant financial relationships.

A version of this article first appeared on Medscape.com.

Contrary to some prior studies, new research suggests that a healthy diet, including the Mediterranean diet, does not reduce dementia risk.

After adjusting for relevant demographic and other lifestyle measures, there was no association between adherence to healthy dietary advice or the Mediterranean diet on the future risk of dementia or amyloid-beta (Abeta) accumulation.

OksanaKiian/Getty Images

“While our study does not rule out a possible association between diet and dementia, we did not find a link in our study, which had a long follow-up period, included younger participants than some other studies and did not require people to remember what foods they had eaten regularly years before,” study investigator Isabelle Glans, MD, of Lund (Sweden) University, said in a news release.

The findings were published online in Neurology.
 

No risk reduction

Several studies have investigated how dietary habits affect dementia risk, with inconsistent results.

The new findings are based on 28,025 adults (61% women; mean age, 58 years at baseline) who were free of dementia at baseline and were followed over a 20-year period as part of the Swedish Malmö Diet and Cancer Study. Dietary habits were assessed with a 7-day food diary, detailed food frequency questionnaire, and in-person interview.

During follow-up, 1,943 individuals (6.9%) developed dementia.

Compared with those who did not develop dementia, those who did develop dementia during follow-up were older and had a lower level of education and more cardiovascular risk factors and comorbidities at baseline.

Individuals who adhered to conventional healthy dietary recommendations did not have a lower risk of developing all-cause dementia (hazard ratio comparing worst with best adherence, 0.93; 95% confidence interval, 0.81-1.08), Alzheimer’s disease (HR, 1.03; 95% CI, 0.85-1.23) or vascular dementia (HR, 0.93; 95% CI, 0.69-1.26).

Adherence to the modified Mediterranean diet also did not appear to lower the risk of all-cause dementia (HR, 0.93; 95% CI, 0.75-1.15), Alzheimer’s disease (HR, 0.90; 95% CI, 0.68-1.19), or vascular dementia (HR, 1.00; 95% CI, 0.65-1.55).

There was also no significant association between diet and Alzheimer’s disease–related pathology, as measured by cerebrospinal fluid analysis of Abeta42 in a subgroup of 738 participants. Various sensitivity analyses yielded similar results.
 

Diet still matters

The authors of an accompanying editorial noted that diet as a “singular factor may not have a strong enough effect on cognition, but is more likely to be considered as one factor embedded with various others, the sum of which may influence the course of cognitive function (diet, regular exercise, vascular risk factor control, avoiding cigarette smoking, drinking alcohol in moderation, etc).

“Diet should not be forgotten and it still matters” but should be regarded as “one part of a multidomain intervention with respect to cognitive performance,” wrote Nils Peters, MD, with the University of Basel (Switzerland), and Benedetta Nacmias, PhD, with the University of Florence (Italy)).

“Key questions that remain include how to provide evidence for promoting the implications of dietary habits on cognition? Overall, dietary strategies will most likely be implicated either in order to reduce the increasing number of older subjects with dementia, or to extend healthy life expectancy, or both,” Dr. Peters and Dr. Nacmias said.

The study had no commercial funding. Dr. Glans, Dr. Peters, and Dr. Nacmias disclosed no relevant financial relationships.

A version of this article first appeared on Medscape.com.

Contrary to some prior studies, new research suggests that a healthy diet, including the Mediterranean diet, does not reduce dementia risk.

After adjusting for relevant demographic and other lifestyle measures, there was no association between adherence to healthy dietary advice or the Mediterranean diet on the future risk of dementia or amyloid-beta (Abeta) accumulation.

OksanaKiian/Getty Images

“While our study does not rule out a possible association between diet and dementia, we did not find a link in our study, which had a long follow-up period, included younger participants than some other studies and did not require people to remember what foods they had eaten regularly years before,” study investigator Isabelle Glans, MD, of Lund (Sweden) University, said in a news release.

The findings were published online in Neurology.
 

No risk reduction

Several studies have investigated how dietary habits affect dementia risk, with inconsistent results.

The new findings are based on 28,025 adults (61% women; mean age, 58 years at baseline) who were free of dementia at baseline and were followed over a 20-year period as part of the Swedish Malmö Diet and Cancer Study. Dietary habits were assessed with a 7-day food diary, detailed food frequency questionnaire, and in-person interview.

During follow-up, 1,943 individuals (6.9%) developed dementia.

Compared with those who did not develop dementia, those who did develop dementia during follow-up were older and had a lower level of education and more cardiovascular risk factors and comorbidities at baseline.

Individuals who adhered to conventional healthy dietary recommendations did not have a lower risk of developing all-cause dementia (hazard ratio comparing worst with best adherence, 0.93; 95% confidence interval, 0.81-1.08), Alzheimer’s disease (HR, 1.03; 95% CI, 0.85-1.23) or vascular dementia (HR, 0.93; 95% CI, 0.69-1.26).

Adherence to the modified Mediterranean diet also did not appear to lower the risk of all-cause dementia (HR, 0.93; 95% CI, 0.75-1.15), Alzheimer’s disease (HR, 0.90; 95% CI, 0.68-1.19), or vascular dementia (HR, 1.00; 95% CI, 0.65-1.55).

There was also no significant association between diet and Alzheimer’s disease–related pathology, as measured by cerebrospinal fluid analysis of Abeta42 in a subgroup of 738 participants. Various sensitivity analyses yielded similar results.
 

Diet still matters

The authors of an accompanying editorial noted that diet as a “singular factor may not have a strong enough effect on cognition, but is more likely to be considered as one factor embedded with various others, the sum of which may influence the course of cognitive function (diet, regular exercise, vascular risk factor control, avoiding cigarette smoking, drinking alcohol in moderation, etc).

“Diet should not be forgotten and it still matters” but should be regarded as “one part of a multidomain intervention with respect to cognitive performance,” wrote Nils Peters, MD, with the University of Basel (Switzerland), and Benedetta Nacmias, PhD, with the University of Florence (Italy)).

“Key questions that remain include how to provide evidence for promoting the implications of dietary habits on cognition? Overall, dietary strategies will most likely be implicated either in order to reduce the increasing number of older subjects with dementia, or to extend healthy life expectancy, or both,” Dr. Peters and Dr. Nacmias said.

The study had no commercial funding. Dr. Glans, Dr. Peters, and Dr. Nacmias disclosed no relevant financial relationships.

A version of this article first appeared on Medscape.com.

CINCINNATI – Dystonia is a frequent complication seen in cerebral palsy, but it often goes undiagnosed. Using a unique video analysis, researchers have identified some movement features that have the potential to simplify diagnosis.

“[We have] previously demonstrated that by the age of 5 years, only 30% of children seen in a clinical setting have had their predominant motor phenotype identified, including dystonia. This helps demonstrate a broad diagnostic gap and the need for novel solutions,” said Laura Gilbert, DO, during her presentation of the results at the 2022 annual meeting of the Child Neurology Society.

Diagnosis of dystonia is challenging because of its clinical variability, and diagnostic tools often require a trained physician, which limits access to diagnoses. Expert clinician consensus therefore remains the gold standard for diagnosis of dystonia.

Another clinical need is that specific features of dystonia have not been well described in the upper extremities, and the research suggests there could be differences in brain injuries contributing to dystonia in the two domains.

The researchers set out to discover expert-identified features of patient videos that could be used to allow nonexperts to make a diagnosis of dystonia.

The researchers analyzed 26 videos with upper extremity exam maneuvers performed on children with periventricular leukomalacia at St. Louis Children’s Hospital Cerebral Palsy Center from 2005 to 2018. Among the study cohort, 65% of patients were male, 77% were White, and 11% were Black; 24% of patients were Gross Motor Function Classification Scale I, 24% were GMFCS II, 24% were GMFCS III, 16% were GMFCS IV, and 12% were GMFCS V. A total of 12% of patients were older than 20, 11% were aged 15-20, 38% were aged 10-15, 31% were aged 5-10, and 8% were age 5 or younger.
 

Video clues aid diagnosis

Three pediatric movement disorder specialists independently reviewed each video and assessed severity of dystonia. They then met over Zoom to reach a diagnostic consensus for each case.

The research team performed a content analysis of the experts’ discussions and identified specific statement fragments. The frequency of these fragments was then linked to severity of dystonia.

A total of 45% of the statement fragments referenced movement codes, which in turn comprised five content areas: 33% referenced a body part, 24% focused on laterality, 22% described movement features, 18% an action, and 3% described exam maneuvers. Examples included shoulder as a body part, flexion as an action descriptor, brisk as a movement feature, unilateral, and finger-nose-finger for exam maneuver.

With increasing dystonia severity, the shoulder was more often cited and hand was cited less often. Mirror movements, defined as involuntary, contralateral movements that are similar to the voluntary action, occurred more often in patients with no dystonia or only mild dystonia. Variability of movement over time, which is a distinguishing feature found in lower extremities, was not significantly associated with dystonia severity.

Within the category of exam maneuver, hand opening and closing was the most commonly cited, and it was cited more frequently among individuals with mild dystonia (70% vs. about 10% for both no dystonia and moderate to severe dystonia; P < .005).

“So how can we adopt this clinically? First, we can add in a very brief exam maneuver of hand opening and closing that can help assess for mild dystonia. Shoulder involvement may suggest more severe dystonia, and we must recognize the dystonia features seem to differ by body region and the triggering task. Overall, to help improve dystonia diagnosis, we must continue to work towards understanding these salient features to fully grasp the breadth of dystonia manifestations in people with [cerebral palsy],” said Dr. Gilbert, who is a pediatric movements disorder fellow at Washington University in St. Louis.
 

Key features help determine dystonia severity

The study is particularly interesting for its different findings in upper extremities versus lower extremities, according to Keith Coffman, MD, who comoderated the session where the study was presented. “That same group showed that there are very clear differences in lower-extremity function, but when they looked at upper extremity, there really weren’t robust differences. What it may show is that the features of cerebral palsy regarding dystonia may be very dependent on what type of injury you have to your brain. Because when you think about where the motor fibers that provide leg function, they live along the medial walls of the brain right along the midline, whereas the representation of the hand and arm are more out on the lateral side of the brain. So it may be that those regional anatomy differences and where the injury occurred could be at the baseline of why they had such differences in motor function,” said Dr. Coffman, who is a professor of pediatrics at University of Missouri–Kansas City and director of the movement disorders program at Children’s Mercy Hospital, also in Kansas City, Mo.

He suggested that the researchers might also do kinematic analysis of the videos to make predictions using quantitative differences in movement.

The research has the potential to improve dystonia diagnosis, according to comoderator Marc Patterson, MD, professor of neurology, pediatrics, and medical genetics at Mayo Clinic in Rochester, Minn. “I think they really pointed to some key features that can help clinicians distinguish [dystonia severity]. Something like the speed of opening and closing the hands [is a] fairly simple thing. That was to me the chief value of that study,” Dr. Patterson said.

Dr. Gilbert reported no relevant disclosures.

CINCINNATI – Dystonia is a frequent complication seen in cerebral palsy, but it often goes undiagnosed. Using a unique video analysis, researchers have identified some movement features that have the potential to simplify diagnosis.

“[We have] previously demonstrated that by the age of 5 years, only 30% of children seen in a clinical setting have had their predominant motor phenotype identified, including dystonia. This helps demonstrate a broad diagnostic gap and the need for novel solutions,” said Laura Gilbert, DO, during her presentation of the results at the 2022 annual meeting of the Child Neurology Society.

Diagnosis of dystonia is challenging because of its clinical variability, and diagnostic tools often require a trained physician, which limits access to diagnoses. Expert clinician consensus therefore remains the gold standard for diagnosis of dystonia.

Another clinical need is that specific features of dystonia have not been well described in the upper extremities, and the research suggests there could be differences in brain injuries contributing to dystonia in the two domains.

The researchers set out to discover expert-identified features of patient videos that could be used to allow nonexperts to make a diagnosis of dystonia.

The researchers analyzed 26 videos with upper extremity exam maneuvers performed on children with periventricular leukomalacia at St. Louis Children’s Hospital Cerebral Palsy Center from 2005 to 2018. Among the study cohort, 65% of patients were male, 77% were White, and 11% were Black; 24% of patients were Gross Motor Function Classification Scale I, 24% were GMFCS II, 24% were GMFCS III, 16% were GMFCS IV, and 12% were GMFCS V. A total of 12% of patients were older than 20, 11% were aged 15-20, 38% were aged 10-15, 31% were aged 5-10, and 8% were age 5 or younger.
 

Video clues aid diagnosis

Three pediatric movement disorder specialists independently reviewed each video and assessed severity of dystonia. They then met over Zoom to reach a diagnostic consensus for each case.

The research team performed a content analysis of the experts’ discussions and identified specific statement fragments. The frequency of these fragments was then linked to severity of dystonia.

A total of 45% of the statement fragments referenced movement codes, which in turn comprised five content areas: 33% referenced a body part, 24% focused on laterality, 22% described movement features, 18% an action, and 3% described exam maneuvers. Examples included shoulder as a body part, flexion as an action descriptor, brisk as a movement feature, unilateral, and finger-nose-finger for exam maneuver.

With increasing dystonia severity, the shoulder was more often cited and hand was cited less often. Mirror movements, defined as involuntary, contralateral movements that are similar to the voluntary action, occurred more often in patients with no dystonia or only mild dystonia. Variability of movement over time, which is a distinguishing feature found in lower extremities, was not significantly associated with dystonia severity.

Within the category of exam maneuver, hand opening and closing was the most commonly cited, and it was cited more frequently among individuals with mild dystonia (70% vs. about 10% for both no dystonia and moderate to severe dystonia; P < .005).

“So how can we adopt this clinically? First, we can add in a very brief exam maneuver of hand opening and closing that can help assess for mild dystonia. Shoulder involvement may suggest more severe dystonia, and we must recognize the dystonia features seem to differ by body region and the triggering task. Overall, to help improve dystonia diagnosis, we must continue to work towards understanding these salient features to fully grasp the breadth of dystonia manifestations in people with [cerebral palsy],” said Dr. Gilbert, who is a pediatric movements disorder fellow at Washington University in St. Louis.
 

Key features help determine dystonia severity

The study is particularly interesting for its different findings in upper extremities versus lower extremities, according to Keith Coffman, MD, who comoderated the session where the study was presented. “That same group showed that there are very clear differences in lower-extremity function, but when they looked at upper extremity, there really weren’t robust differences. What it may show is that the features of cerebral palsy regarding dystonia may be very dependent on what type of injury you have to your brain. Because when you think about where the motor fibers that provide leg function, they live along the medial walls of the brain right along the midline, whereas the representation of the hand and arm are more out on the lateral side of the brain. So it may be that those regional anatomy differences and where the injury occurred could be at the baseline of why they had such differences in motor function,” said Dr. Coffman, who is a professor of pediatrics at University of Missouri–Kansas City and director of the movement disorders program at Children’s Mercy Hospital, also in Kansas City, Mo.

He suggested that the researchers might also do kinematic analysis of the videos to make predictions using quantitative differences in movement.

The research has the potential to improve dystonia diagnosis, according to comoderator Marc Patterson, MD, professor of neurology, pediatrics, and medical genetics at Mayo Clinic in Rochester, Minn. “I think they really pointed to some key features that can help clinicians distinguish [dystonia severity]. Something like the speed of opening and closing the hands [is a] fairly simple thing. That was to me the chief value of that study,” Dr. Patterson said.

Dr. Gilbert reported no relevant disclosures.

CINCINNATI – Dystonia is a frequent complication seen in cerebral palsy, but it often goes undiagnosed. Using a unique video analysis, researchers have identified some movement features that have the potential to simplify diagnosis.

“[We have] previously demonstrated that by the age of 5 years, only 30% of children seen in a clinical setting have had their predominant motor phenotype identified, including dystonia. This helps demonstrate a broad diagnostic gap and the need for novel solutions,” said Laura Gilbert, DO, during her presentation of the results at the 2022 annual meeting of the Child Neurology Society.

Diagnosis of dystonia is challenging because of its clinical variability, and diagnostic tools often require a trained physician, which limits access to diagnoses. Expert clinician consensus therefore remains the gold standard for diagnosis of dystonia.

Another clinical need is that specific features of dystonia have not been well described in the upper extremities, and the research suggests there could be differences in brain injuries contributing to dystonia in the two domains.

The researchers set out to discover expert-identified features of patient videos that could be used to allow nonexperts to make a diagnosis of dystonia.

The researchers analyzed 26 videos with upper extremity exam maneuvers performed on children with periventricular leukomalacia at St. Louis Children’s Hospital Cerebral Palsy Center from 2005 to 2018. Among the study cohort, 65% of patients were male, 77% were White, and 11% were Black; 24% of patients were Gross Motor Function Classification Scale I, 24% were GMFCS II, 24% were GMFCS III, 16% were GMFCS IV, and 12% were GMFCS V. A total of 12% of patients were older than 20, 11% were aged 15-20, 38% were aged 10-15, 31% were aged 5-10, and 8% were age 5 or younger.
 

Video clues aid diagnosis

Three pediatric movement disorder specialists independently reviewed each video and assessed severity of dystonia. They then met over Zoom to reach a diagnostic consensus for each case.

The research team performed a content analysis of the experts’ discussions and identified specific statement fragments. The frequency of these fragments was then linked to severity of dystonia.

A total of 45% of the statement fragments referenced movement codes, which in turn comprised five content areas: 33% referenced a body part, 24% focused on laterality, 22% described movement features, 18% an action, and 3% described exam maneuvers. Examples included shoulder as a body part, flexion as an action descriptor, brisk as a movement feature, unilateral, and finger-nose-finger for exam maneuver.

With increasing dystonia severity, the shoulder was more often cited and hand was cited less often. Mirror movements, defined as involuntary, contralateral movements that are similar to the voluntary action, occurred more often in patients with no dystonia or only mild dystonia. Variability of movement over time, which is a distinguishing feature found in lower extremities, was not significantly associated with dystonia severity.

Within the category of exam maneuver, hand opening and closing was the most commonly cited, and it was cited more frequently among individuals with mild dystonia (70% vs. about 10% for both no dystonia and moderate to severe dystonia; P < .005).

“So how can we adopt this clinically? First, we can add in a very brief exam maneuver of hand opening and closing that can help assess for mild dystonia. Shoulder involvement may suggest more severe dystonia, and we must recognize the dystonia features seem to differ by body region and the triggering task. Overall, to help improve dystonia diagnosis, we must continue to work towards understanding these salient features to fully grasp the breadth of dystonia manifestations in people with [cerebral palsy],” said Dr. Gilbert, who is a pediatric movements disorder fellow at Washington University in St. Louis.
 

Key features help determine dystonia severity

The study is particularly interesting for its different findings in upper extremities versus lower extremities, according to Keith Coffman, MD, who comoderated the session where the study was presented. “That same group showed that there are very clear differences in lower-extremity function, but when they looked at upper extremity, there really weren’t robust differences. What it may show is that the features of cerebral palsy regarding dystonia may be very dependent on what type of injury you have to your brain. Because when you think about where the motor fibers that provide leg function, they live along the medial walls of the brain right along the midline, whereas the representation of the hand and arm are more out on the lateral side of the brain. So it may be that those regional anatomy differences and where the injury occurred could be at the baseline of why they had such differences in motor function,” said Dr. Coffman, who is a professor of pediatrics at University of Missouri–Kansas City and director of the movement disorders program at Children’s Mercy Hospital, also in Kansas City, Mo.

He suggested that the researchers might also do kinematic analysis of the videos to make predictions using quantitative differences in movement.

The research has the potential to improve dystonia diagnosis, according to comoderator Marc Patterson, MD, professor of neurology, pediatrics, and medical genetics at Mayo Clinic in Rochester, Minn. “I think they really pointed to some key features that can help clinicians distinguish [dystonia severity]. Something like the speed of opening and closing the hands [is a] fairly simple thing. That was to me the chief value of that study,” Dr. Patterson said.

Dr. Gilbert reported no relevant disclosures.

Teens diagnosed with attention-deficit/hyperactivity disorder in childhood reported similar overall quality of life compared with teens with ADHD behaviors but no childhood diagnosis, a new study finds.

The results align with findings from other studies suggesting lower quality of life (QOL) in teens with ADHD, but the current study is the first known to focus on the association between ADHD diagnosis itself vs. ADHD symptoms, and QOL, the researchers wrote. The findings show that at least some of the reduced QOL is associated with the diagnosis itself, they explained.

The researchers directly compared 393 teens with a childhood ADHD diagnosis to 393 matched teens with no ADHD diagnosis but who had hyperactive/inattentive behaviors.

The researchers reviewed self-reports from individuals who were enrolled in a population-based prospective study in Australia. The primary outcome was quality of life at age 14-15, which was measured with Child Health Utility 9D (CHU9D), a validated quality of life measure.
 

Study results

Overall, teens with and without an ADHD diagnosis reported similar levels of overall quality of life; the mean difference in the primary outcome CHU9D score was –0.03 (P = .10). Teens with and without an ADHD diagnosis also showed similar scores on measures of general health, happiness, and peer trust, the researchers noted.

The researchers also reviewed eight other prespecified, self-reported measures: academic self-concept, global health, negative social behaviors, overall happiness, peer trust, psychological sense of school membership, self-efficacy, and self-harm.

Teens diagnosed with ADHD in childhood were more than twice as likely to report self-harm (odds ratio 2.53, P less than .001) and displayed significantly more negative social behaviors (mean difference 1.56, P = .002), compared with teens without an ADHD diagnosis.

Teens diagnosed with ADHD in childhood also scored significantly worse on measures of sense of school membership (mean difference −2.58, P less than .001), academic self-concept (mean difference, −0.14; P = .02), and self-efficacy (mean difference −0.20; P = .007), compared to teens without an ADHD diagnosis.

The average age at ADHD diagnosis was 10 years, and 72% of the ADHD-diagnosed group were boys. No significant differences were noted for levels of hyperactive/inattentive behaviors and between girls and boys, but girls overall and children with the highest levels of hyperactive and inattentive behaviors reported generally worse outcomes, regardless of ADHD diagnosis, the researchers noted.
 

Don’t rush to diagnosis

Although rates of ADHD diagnosis in children continue to rise, the prevalence of hyperactivity and inattentive behaviors appears stable, which suggests a problem with diagnosis, senior author Alexandra Barratt, MBBS, MPH, PhD, professor of public health at the University of Sydney, Australia, said in an interview.

“Our hypothesis was that children who had been diagnosed, and we assume treated for, ADHD would have better outcomes, compared to children matched for hyperactivity/inattention behaviors who were left undiagnosed and untreated, but we were surprised to find that, at best, outcomes were unchanged, and for some outcomes, worse,” Dr. Barratt said.

“Our study provides evidence that diagnosing ADHD may lead, inadvertently, to long-term harms, particularly for children with mild or borderline hyperactivity and inattention behaviors,” she emphasized.

“We can’t say from this study what to do instead, but previously one of our team has looked at stepped diagnosis as an alternative option for children with mild or borderline hyperactivity and inattention behaviors,” she said.

The stepped diagnosis includes such actions as gathering behavior data from multiple sources, and conducting a period of watchful waiting without presumption of a diagnosis or active treatment.

Given the findings of the new study, “I would ask that health professionals considering a child who may have ADHD be aware that there is an evidence gap around the long-term impact of an ADHD diagnosis on children, and to proceed cautiously,” Dr. Barratt said. As for additional research, independent, high-quality, randomized controlled trials of ADHD diagnosis in children with mild or borderline hyperactivity/inattention behaviors are urgently needed, with long-term, patient-centered outcomes including quality of life she noted.

ADHD screening needs improvement

The incidence and prevalence of ADHD is on the rise, but much of the perceived increase in ADHD may be due to overdiagnosis, “and a lack of robust thorough psychological testing as standard of care for diagnosis,” Peter Loper, MD, a pediatrician and psychiatrist at the University of South Carolina, Columbia, said in an interview.

The current study “reinforces the necessity of consistent screening for comorbid mental health problems, and specifically for thoughts of self-harm, in those children who are diagnosed with ADHD,” he said.

Expressing his lack of astonishment about the study findings, Dr. Loper said: “Previous data indicates that while following initial diagnosis of a medical or mental health problem, patients may experience a sense of relief; however, this is followed shortly thereafter by feelings of insufficiency or anxiety related to their specific diagnosis.”

“As it stands now, ADHD is often diagnosed in children and adolescents using basic screening questionnaires,” said Dr. Loper. “The findings of this study may bolster calls for more robust and thorough psychological testing for supporting the diagnosis of ADHD,” he said.

Individuals diagnosed with ADHD can sometimes have difficulty with social skills and relating to others, said Dr. Loper. “They may be more prone to internalize their poor school performance as due to being ‘stupid’ or ‘dumb,’ ” he said. Children and teens with ADHD should, whenever possible, be involved in extracurricular activities that support the development of social skills, he said. Parents’ praise of the process/effort, rather than focusing only on outcomes such as grades, is very important for the esteem of children and teens with ADHD, he added.

The study limitations included the use of observational data vs. data from randomized trials, and the potential for confounding factors in propensity scoring, the researchers wrote. Additional limitations include the size of the sample, which may have been too small to detect additional differences between diagnosed teens and matched controls, they noted.

“As the study authors appropriately cite, a large, randomized trial would be very helpful in supporting additional understanding of this issue,” Dr. Loper added.

The study was supported by the National Health and Medical Research Council The researchers and Dr. Loper had no financial conflicts to disclose.

Teens diagnosed with attention-deficit/hyperactivity disorder in childhood reported similar overall quality of life compared with teens with ADHD behaviors but no childhood diagnosis, a new study finds.

The results align with findings from other studies suggesting lower quality of life (QOL) in teens with ADHD, but the current study is the first known to focus on the association between ADHD diagnosis itself vs. ADHD symptoms, and QOL, the researchers wrote. The findings show that at least some of the reduced QOL is associated with the diagnosis itself, they explained.

The researchers directly compared 393 teens with a childhood ADHD diagnosis to 393 matched teens with no ADHD diagnosis but who had hyperactive/inattentive behaviors.

The researchers reviewed self-reports from individuals who were enrolled in a population-based prospective study in Australia. The primary outcome was quality of life at age 14-15, which was measured with Child Health Utility 9D (CHU9D), a validated quality of life measure.
 

Study results

Overall, teens with and without an ADHD diagnosis reported similar levels of overall quality of life; the mean difference in the primary outcome CHU9D score was –0.03 (P = .10). Teens with and without an ADHD diagnosis also showed similar scores on measures of general health, happiness, and peer trust, the researchers noted.

The researchers also reviewed eight other prespecified, self-reported measures: academic self-concept, global health, negative social behaviors, overall happiness, peer trust, psychological sense of school membership, self-efficacy, and self-harm.

Teens diagnosed with ADHD in childhood were more than twice as likely to report self-harm (odds ratio 2.53, P less than .001) and displayed significantly more negative social behaviors (mean difference 1.56, P = .002), compared with teens without an ADHD diagnosis.

Teens diagnosed with ADHD in childhood also scored significantly worse on measures of sense of school membership (mean difference −2.58, P less than .001), academic self-concept (mean difference, −0.14; P = .02), and self-efficacy (mean difference −0.20; P = .007), compared to teens without an ADHD diagnosis.

The average age at ADHD diagnosis was 10 years, and 72% of the ADHD-diagnosed group were boys. No significant differences were noted for levels of hyperactive/inattentive behaviors and between girls and boys, but girls overall and children with the highest levels of hyperactive and inattentive behaviors reported generally worse outcomes, regardless of ADHD diagnosis, the researchers noted.
 

Don’t rush to diagnosis

Although rates of ADHD diagnosis in children continue to rise, the prevalence of hyperactivity and inattentive behaviors appears stable, which suggests a problem with diagnosis, senior author Alexandra Barratt, MBBS, MPH, PhD, professor of public health at the University of Sydney, Australia, said in an interview.

“Our hypothesis was that children who had been diagnosed, and we assume treated for, ADHD would have better outcomes, compared to children matched for hyperactivity/inattention behaviors who were left undiagnosed and untreated, but we were surprised to find that, at best, outcomes were unchanged, and for some outcomes, worse,” Dr. Barratt said.

“Our study provides evidence that diagnosing ADHD may lead, inadvertently, to long-term harms, particularly for children with mild or borderline hyperactivity and inattention behaviors,” she emphasized.

“We can’t say from this study what to do instead, but previously one of our team has looked at stepped diagnosis as an alternative option for children with mild or borderline hyperactivity and inattention behaviors,” she said.

The stepped diagnosis includes such actions as gathering behavior data from multiple sources, and conducting a period of watchful waiting without presumption of a diagnosis or active treatment.

Given the findings of the new study, “I would ask that health professionals considering a child who may have ADHD be aware that there is an evidence gap around the long-term impact of an ADHD diagnosis on children, and to proceed cautiously,” Dr. Barratt said. As for additional research, independent, high-quality, randomized controlled trials of ADHD diagnosis in children with mild or borderline hyperactivity/inattention behaviors are urgently needed, with long-term, patient-centered outcomes including quality of life she noted.

ADHD screening needs improvement

The incidence and prevalence of ADHD is on the rise, but much of the perceived increase in ADHD may be due to overdiagnosis, “and a lack of robust thorough psychological testing as standard of care for diagnosis,” Peter Loper, MD, a pediatrician and psychiatrist at the University of South Carolina, Columbia, said in an interview.

The current study “reinforces the necessity of consistent screening for comorbid mental health problems, and specifically for thoughts of self-harm, in those children who are diagnosed with ADHD,” he said.

Expressing his lack of astonishment about the study findings, Dr. Loper said: “Previous data indicates that while following initial diagnosis of a medical or mental health problem, patients may experience a sense of relief; however, this is followed shortly thereafter by feelings of insufficiency or anxiety related to their specific diagnosis.”

“As it stands now, ADHD is often diagnosed in children and adolescents using basic screening questionnaires,” said Dr. Loper. “The findings of this study may bolster calls for more robust and thorough psychological testing for supporting the diagnosis of ADHD,” he said.

Individuals diagnosed with ADHD can sometimes have difficulty with social skills and relating to others, said Dr. Loper. “They may be more prone to internalize their poor school performance as due to being ‘stupid’ or ‘dumb,’ ” he said. Children and teens with ADHD should, whenever possible, be involved in extracurricular activities that support the development of social skills, he said. Parents’ praise of the process/effort, rather than focusing only on outcomes such as grades, is very important for the esteem of children and teens with ADHD, he added.

The study limitations included the use of observational data vs. data from randomized trials, and the potential for confounding factors in propensity scoring, the researchers wrote. Additional limitations include the size of the sample, which may have been too small to detect additional differences between diagnosed teens and matched controls, they noted.

“As the study authors appropriately cite, a large, randomized trial would be very helpful in supporting additional understanding of this issue,” Dr. Loper added.

The study was supported by the National Health and Medical Research Council The researchers and Dr. Loper had no financial conflicts to disclose.

Teens diagnosed with attention-deficit/hyperactivity disorder in childhood reported similar overall quality of life compared with teens with ADHD behaviors but no childhood diagnosis, a new study finds.

The results align with findings from other studies suggesting lower quality of life (QOL) in teens with ADHD, but the current study is the first known to focus on the association between ADHD diagnosis itself vs. ADHD symptoms, and QOL, the researchers wrote. The findings show that at least some of the reduced QOL is associated with the diagnosis itself, they explained.

The researchers directly compared 393 teens with a childhood ADHD diagnosis to 393 matched teens with no ADHD diagnosis but who had hyperactive/inattentive behaviors.

The researchers reviewed self-reports from individuals who were enrolled in a population-based prospective study in Australia. The primary outcome was quality of life at age 14-15, which was measured with Child Health Utility 9D (CHU9D), a validated quality of life measure.
 

Study results

Overall, teens with and without an ADHD diagnosis reported similar levels of overall quality of life; the mean difference in the primary outcome CHU9D score was –0.03 (P = .10). Teens with and without an ADHD diagnosis also showed similar scores on measures of general health, happiness, and peer trust, the researchers noted.

The researchers also reviewed eight other prespecified, self-reported measures: academic self-concept, global health, negative social behaviors, overall happiness, peer trust, psychological sense of school membership, self-efficacy, and self-harm.

Teens diagnosed with ADHD in childhood were more than twice as likely to report self-harm (odds ratio 2.53, P less than .001) and displayed significantly more negative social behaviors (mean difference 1.56, P = .002), compared with teens without an ADHD diagnosis.

Teens diagnosed with ADHD in childhood also scored significantly worse on measures of sense of school membership (mean difference −2.58, P less than .001), academic self-concept (mean difference, −0.14; P = .02), and self-efficacy (mean difference −0.20; P = .007), compared to teens without an ADHD diagnosis.

The average age at ADHD diagnosis was 10 years, and 72% of the ADHD-diagnosed group were boys. No significant differences were noted for levels of hyperactive/inattentive behaviors and between girls and boys, but girls overall and children with the highest levels of hyperactive and inattentive behaviors reported generally worse outcomes, regardless of ADHD diagnosis, the researchers noted.
 

Don’t rush to diagnosis

Although rates of ADHD diagnosis in children continue to rise, the prevalence of hyperactivity and inattentive behaviors appears stable, which suggests a problem with diagnosis, senior author Alexandra Barratt, MBBS, MPH, PhD, professor of public health at the University of Sydney, Australia, said in an interview.

“Our hypothesis was that children who had been diagnosed, and we assume treated for, ADHD would have better outcomes, compared to children matched for hyperactivity/inattention behaviors who were left undiagnosed and untreated, but we were surprised to find that, at best, outcomes were unchanged, and for some outcomes, worse,” Dr. Barratt said.

“Our study provides evidence that diagnosing ADHD may lead, inadvertently, to long-term harms, particularly for children with mild or borderline hyperactivity and inattention behaviors,” she emphasized.

“We can’t say from this study what to do instead, but previously one of our team has looked at stepped diagnosis as an alternative option for children with mild or borderline hyperactivity and inattention behaviors,” she said.

The stepped diagnosis includes such actions as gathering behavior data from multiple sources, and conducting a period of watchful waiting without presumption of a diagnosis or active treatment.

Given the findings of the new study, “I would ask that health professionals considering a child who may have ADHD be aware that there is an evidence gap around the long-term impact of an ADHD diagnosis on children, and to proceed cautiously,” Dr. Barratt said. As for additional research, independent, high-quality, randomized controlled trials of ADHD diagnosis in children with mild or borderline hyperactivity/inattention behaviors are urgently needed, with long-term, patient-centered outcomes including quality of life she noted.

ADHD screening needs improvement

The incidence and prevalence of ADHD is on the rise, but much of the perceived increase in ADHD may be due to overdiagnosis, “and a lack of robust thorough psychological testing as standard of care for diagnosis,” Peter Loper, MD, a pediatrician and psychiatrist at the University of South Carolina, Columbia, said in an interview.

The current study “reinforces the necessity of consistent screening for comorbid mental health problems, and specifically for thoughts of self-harm, in those children who are diagnosed with ADHD,” he said.

Expressing his lack of astonishment about the study findings, Dr. Loper said: “Previous data indicates that while following initial diagnosis of a medical or mental health problem, patients may experience a sense of relief; however, this is followed shortly thereafter by feelings of insufficiency or anxiety related to their specific diagnosis.”

“As it stands now, ADHD is often diagnosed in children and adolescents using basic screening questionnaires,” said Dr. Loper. “The findings of this study may bolster calls for more robust and thorough psychological testing for supporting the diagnosis of ADHD,” he said.

Individuals diagnosed with ADHD can sometimes have difficulty with social skills and relating to others, said Dr. Loper. “They may be more prone to internalize their poor school performance as due to being ‘stupid’ or ‘dumb,’ ” he said. Children and teens with ADHD should, whenever possible, be involved in extracurricular activities that support the development of social skills, he said. Parents’ praise of the process/effort, rather than focusing only on outcomes such as grades, is very important for the esteem of children and teens with ADHD, he added.

The study limitations included the use of observational data vs. data from randomized trials, and the potential for confounding factors in propensity scoring, the researchers wrote. Additional limitations include the size of the sample, which may have been too small to detect additional differences between diagnosed teens and matched controls, they noted.

“As the study authors appropriately cite, a large, randomized trial would be very helpful in supporting additional understanding of this issue,” Dr. Loper added.

The study was supported by the National Health and Medical Research Council The researchers and Dr. Loper had no financial conflicts to disclose.

U.K. scientists show it is possible to spot signs of brain impairment in patients as early as 9 years before they receive a diagnosis of dementia, offering hope for interventions to reduce the risk of the disease developing.

To date it has been unclear whether it might be possible to detect changes in brain function before the onset of symptoms, so researchers at the University of Cambridge and Cambridge University Hospitals NHS Foundation Trust set out to determine whether people who developed a range of neurodegenerative diagnoses demonstrated reduced cognitive function at their baseline assessment.

The authors explained: “The pathophysiological processes of neurodegenerative diseases begin years before diagnosis. However, prediagnostic changes in cognition and physical function are poorly understood, especially in sporadic neurodegenerative disease.”
 

Prediagnostic cognitive and functional impairment identified

The researchers analyzed data from the UK Biobank and compared cognitive and functional measures, including problem solving, memory, reaction times and grip strength, as well as data on weight loss and gain and on the number of falls, in individuals who subsequently developed a number of dementia-related diseases (Alzheimer’s disease, Parkinson’s disease, frontotemporal dementia, progressive supranuclear palsy, dementia with Lewy bodies, and multiple system atrophy), with those who did not have a neurodegenerative diagnosis. After adjustment for the effects of age, the same measures were regressed against time to diagnosis. The study was published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.

The researchers found evidence of prediagnostic cognitive impairment and decline with time, particularly in Alzheimer’s disease where those who went on to develop the disease scored more poorly compared with healthy individuals when it came to problem solving tasks, reaction times, remembering lists of numbers, prospective memory, and pair matching. This was also the case for people who developed frontotemporal dementia, the authors said.

Nol Swaddiwudhipong, MB, of the University of Cambridge, and first author, said: “When we looked back at patients’ histories, it became clear that they were showing some cognitive impairment several years before their symptoms became obvious enough to prompt a diagnosis. The impairments were often subtle, but across a number of aspects of cognition.”

Prediagnostic functional impairment and decline was also observed in multiple diseases, the authors said. People who went on to develop Alzheimer’s disease were more likely than were healthy adults to have had a fall in the previous 12 months, with those patients who went on to develop progressive supranuclear palsy (PSP) being more than twice as likely as healthy individuals to have had a fall.

The time between baseline assessment and diagnosis varied between 4.7 years for dementia with Lewy bodies and 8.3 years for Alzheimer’s disease.

“For every condition studied – including Parkinson’s disease and dementia with Lewy bodies – patients reported poorer overall health at baseline,” said the authors.
 

Potential for new treatments

The study findings that cognitive and functional decline occurs “years before symptoms become obvious” in multiple neurodegenerative diseases, raises the possibility that in the future at-risk patients could be screened to help select those who would benefit from interventions to reduce their risk of developing one of the conditions, or to help identify patients suitable for recruitment to clinical trials for new treatments.

Dr Swaddiwudhipong emphasized: “This is a step towards us being able to screen people who are at greatest risk – for example, people over 50 or those who have high blood pressure or do not do enough exercise – and intervene at an earlier stage to help them reduce their risk.”

There are currently very few effective treatments for dementia or other forms of neurodegeneration, the authors pointed out, in part because these conditions are often only diagnosed once symptoms appear, whereas the underlying neurodegeneration may have “begun years, even decades, earlier.” This means that by the time patients take part in clinical trials, it may already be too late in the disease process to alter its course, they explained.

Timothy Rittman, BMBS, PhD, department of clinical neurosciences, University of Cambridge, and senior author, explained that the findings could also help identify people who can participate in clinical trials for potential new treatments. “The problem with clinical trials is that by necessity they often recruit patients with a diagnosis, but we know that by this point they are already some way down the road and their condition cannot be stopped. If we can find these individuals early enough, we’ll have a better chance of seeing if the drugs are effective,” he emphasized.

Commenting on the new research, Richard Oakley, PhD, associate director of research at Alzheimer’s Society, said: “Studies like this show the importance in continued investment in dementia research to revolutionize diagnosis and drive new treatments, so one day we will beat dementia.”

The research was funded by the Medical Research Council with support from the NIHR Cambridge Biomedical Research Centre. The authors reported no conflicts of interest.

A version of this article first appeared on Medscape UK.

U.K. scientists show it is possible to spot signs of brain impairment in patients as early as 9 years before they receive a diagnosis of dementia, offering hope for interventions to reduce the risk of the disease developing.

To date it has been unclear whether it might be possible to detect changes in brain function before the onset of symptoms, so researchers at the University of Cambridge and Cambridge University Hospitals NHS Foundation Trust set out to determine whether people who developed a range of neurodegenerative diagnoses demonstrated reduced cognitive function at their baseline assessment.

The authors explained: “The pathophysiological processes of neurodegenerative diseases begin years before diagnosis. However, prediagnostic changes in cognition and physical function are poorly understood, especially in sporadic neurodegenerative disease.”
 

Prediagnostic cognitive and functional impairment identified

The researchers analyzed data from the UK Biobank and compared cognitive and functional measures, including problem solving, memory, reaction times and grip strength, as well as data on weight loss and gain and on the number of falls, in individuals who subsequently developed a number of dementia-related diseases (Alzheimer’s disease, Parkinson’s disease, frontotemporal dementia, progressive supranuclear palsy, dementia with Lewy bodies, and multiple system atrophy), with those who did not have a neurodegenerative diagnosis. After adjustment for the effects of age, the same measures were regressed against time to diagnosis. The study was published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.

The researchers found evidence of prediagnostic cognitive impairment and decline with time, particularly in Alzheimer’s disease where those who went on to develop the disease scored more poorly compared with healthy individuals when it came to problem solving tasks, reaction times, remembering lists of numbers, prospective memory, and pair matching. This was also the case for people who developed frontotemporal dementia, the authors said.

Nol Swaddiwudhipong, MB, of the University of Cambridge, and first author, said: “When we looked back at patients’ histories, it became clear that they were showing some cognitive impairment several years before their symptoms became obvious enough to prompt a diagnosis. The impairments were often subtle, but across a number of aspects of cognition.”

Prediagnostic functional impairment and decline was also observed in multiple diseases, the authors said. People who went on to develop Alzheimer’s disease were more likely than were healthy adults to have had a fall in the previous 12 months, with those patients who went on to develop progressive supranuclear palsy (PSP) being more than twice as likely as healthy individuals to have had a fall.

The time between baseline assessment and diagnosis varied between 4.7 years for dementia with Lewy bodies and 8.3 years for Alzheimer’s disease.

“For every condition studied – including Parkinson’s disease and dementia with Lewy bodies – patients reported poorer overall health at baseline,” said the authors.
 

Potential for new treatments

The study findings that cognitive and functional decline occurs “years before symptoms become obvious” in multiple neurodegenerative diseases, raises the possibility that in the future at-risk patients could be screened to help select those who would benefit from interventions to reduce their risk of developing one of the conditions, or to help identify patients suitable for recruitment to clinical trials for new treatments.

Dr Swaddiwudhipong emphasized: “This is a step towards us being able to screen people who are at greatest risk – for example, people over 50 or those who have high blood pressure or do not do enough exercise – and intervene at an earlier stage to help them reduce their risk.”

There are currently very few effective treatments for dementia or other forms of neurodegeneration, the authors pointed out, in part because these conditions are often only diagnosed once symptoms appear, whereas the underlying neurodegeneration may have “begun years, even decades, earlier.” This means that by the time patients take part in clinical trials, it may already be too late in the disease process to alter its course, they explained.

Timothy Rittman, BMBS, PhD, department of clinical neurosciences, University of Cambridge, and senior author, explained that the findings could also help identify people who can participate in clinical trials for potential new treatments. “The problem with clinical trials is that by necessity they often recruit patients with a diagnosis, but we know that by this point they are already some way down the road and their condition cannot be stopped. If we can find these individuals early enough, we’ll have a better chance of seeing if the drugs are effective,” he emphasized.

Commenting on the new research, Richard Oakley, PhD, associate director of research at Alzheimer’s Society, said: “Studies like this show the importance in continued investment in dementia research to revolutionize diagnosis and drive new treatments, so one day we will beat dementia.”

The research was funded by the Medical Research Council with support from the NIHR Cambridge Biomedical Research Centre. The authors reported no conflicts of interest.

A version of this article first appeared on Medscape UK.

U.K. scientists show it is possible to spot signs of brain impairment in patients as early as 9 years before they receive a diagnosis of dementia, offering hope for interventions to reduce the risk of the disease developing.

To date it has been unclear whether it might be possible to detect changes in brain function before the onset of symptoms, so researchers at the University of Cambridge and Cambridge University Hospitals NHS Foundation Trust set out to determine whether people who developed a range of neurodegenerative diagnoses demonstrated reduced cognitive function at their baseline assessment.

The authors explained: “The pathophysiological processes of neurodegenerative diseases begin years before diagnosis. However, prediagnostic changes in cognition and physical function are poorly understood, especially in sporadic neurodegenerative disease.”
 

Prediagnostic cognitive and functional impairment identified

The researchers analyzed data from the UK Biobank and compared cognitive and functional measures, including problem solving, memory, reaction times and grip strength, as well as data on weight loss and gain and on the number of falls, in individuals who subsequently developed a number of dementia-related diseases (Alzheimer’s disease, Parkinson’s disease, frontotemporal dementia, progressive supranuclear palsy, dementia with Lewy bodies, and multiple system atrophy), with those who did not have a neurodegenerative diagnosis. After adjustment for the effects of age, the same measures were regressed against time to diagnosis. The study was published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.

The researchers found evidence of prediagnostic cognitive impairment and decline with time, particularly in Alzheimer’s disease where those who went on to develop the disease scored more poorly compared with healthy individuals when it came to problem solving tasks, reaction times, remembering lists of numbers, prospective memory, and pair matching. This was also the case for people who developed frontotemporal dementia, the authors said.

Nol Swaddiwudhipong, MB, of the University of Cambridge, and first author, said: “When we looked back at patients’ histories, it became clear that they were showing some cognitive impairment several years before their symptoms became obvious enough to prompt a diagnosis. The impairments were often subtle, but across a number of aspects of cognition.”

Prediagnostic functional impairment and decline was also observed in multiple diseases, the authors said. People who went on to develop Alzheimer’s disease were more likely than were healthy adults to have had a fall in the previous 12 months, with those patients who went on to develop progressive supranuclear palsy (PSP) being more than twice as likely as healthy individuals to have had a fall.

The time between baseline assessment and diagnosis varied between 4.7 years for dementia with Lewy bodies and 8.3 years for Alzheimer’s disease.

“For every condition studied – including Parkinson’s disease and dementia with Lewy bodies – patients reported poorer overall health at baseline,” said the authors.
 

Potential for new treatments

The study findings that cognitive and functional decline occurs “years before symptoms become obvious” in multiple neurodegenerative diseases, raises the possibility that in the future at-risk patients could be screened to help select those who would benefit from interventions to reduce their risk of developing one of the conditions, or to help identify patients suitable for recruitment to clinical trials for new treatments.

Dr Swaddiwudhipong emphasized: “This is a step towards us being able to screen people who are at greatest risk – for example, people over 50 or those who have high blood pressure or do not do enough exercise – and intervene at an earlier stage to help them reduce their risk.”

There are currently very few effective treatments for dementia or other forms of neurodegeneration, the authors pointed out, in part because these conditions are often only diagnosed once symptoms appear, whereas the underlying neurodegeneration may have “begun years, even decades, earlier.” This means that by the time patients take part in clinical trials, it may already be too late in the disease process to alter its course, they explained.

Timothy Rittman, BMBS, PhD, department of clinical neurosciences, University of Cambridge, and senior author, explained that the findings could also help identify people who can participate in clinical trials for potential new treatments. “The problem with clinical trials is that by necessity they often recruit patients with a diagnosis, but we know that by this point they are already some way down the road and their condition cannot be stopped. If we can find these individuals early enough, we’ll have a better chance of seeing if the drugs are effective,” he emphasized.

Commenting on the new research, Richard Oakley, PhD, associate director of research at Alzheimer’s Society, said: “Studies like this show the importance in continued investment in dementia research to revolutionize diagnosis and drive new treatments, so one day we will beat dementia.”

The research was funded by the Medical Research Council with support from the NIHR Cambridge Biomedical Research Centre. The authors reported no conflicts of interest.

A version of this article first appeared on Medscape UK.

Tourette syndrome, attention-deficit/hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), and autism spectrum disorder (ASD) share significant overlap in symptomatology, and it can be challenging at times to distinguish between these conditions. Being able to do so, however, can help guide more targeted interventions and accommodations to optimize a patient’s level of functioning.

Oregon Health &amp; Science University (OHSU)

Case example

A healthy, bright 6-year-old boy is referred by his family doctor to an academic medical center for a full team evaluation because of suspicion of ASD, after having already been diagnosed with ADHD at the age of 5. His difficulties with inattention, impulsivity, and hyperactivity, as well as his behavioral rigidities and sensory avoidant and sensory seeking behaviors have caused functional impairments for him in his kindergarten classroom. He has been penalized with removal of recess on more than one occasion. A low dose of a stimulant had been tried but resulted in a perceived increase in disruptive behaviors.

The boy, while hyperkinetic and often paying poor attention, is quite capable of high-quality and well-modulated eye contact paired with typical social referencing and reciprocity when actively engaging with the examiner and his parents. He does have a reported history of serial fixated interests and some repetitive behaviors but is also noted to be flexible in his interpersonal style, maintains other varied and typical interests, easily directs affect, utilizes a wide array of fluid gestures paired naturally with verbal communication, and shares enjoyment with smoothly coordinated gaze. He has mild articulation errors but uses pronouns appropriately and has no scripted speech or echolalia, though does engage in some whispered palilalia intermittently.

He is generally quite cooperative and redirectable when focused and has a completely normal physical and neurologic examination. During the visit, the doctor notices the boy making an intermittent honking sound, which parents report as an attention-seeking strategy during times of stress. Further physician-guided information gathering around other repetitive noises and movements elicits a history of engagement in repetitive hand-to-groin movements, some exaggerated blinking, and a number of other waxing and waning subtle motor and phonic tics with onset in preschool. These noises and movements have generally been identified as “fidgeting” and “misbehaving” by well-meaning caregivers in the home and school environments.

Both Tourette syndrome and ASD are more common in males, with stereotyped patterns of movements and behaviors; anxious, obsessive, and compulsive behaviors resulting in behavioral rigidities; sensory sensitivities; and increased rates of hyperkinesis with decreased impulse control which result in increased sensory-seeking behaviors. Diagnostic criteria for Tourette syndrome are met when a child has had multiple motor tics and at least one phonic tic present for at least 1 year, with tic-free intervals lasting no longer than 3 months, and with onset before the age of 18. Typically, tics emerge in late preschool and early grade school, and some children even develop repetitive movements as early as toddlerhood. Tics tend to worsen around the peripubertal era, then often generally improve in the teen years. Tic types, frequency, and severity general fluctuate over time.

Forty percent of children with Tourette syndrome also meet criteria for OCD, with many more having OCD traits, and about 65% of children with Tourette syndrome also meet criteria for ADHD, with many more having ADHD traits. OCD can lead to more rigid and directive social interactions in children as well as obsessive interests, just as ADHD can lead to less socially attuned and less cooperative behaviors, even in children who do not meet criteria for ASD.

For example, a child with OCD in the absence of ASD may still “police” other kids in class and be overly focused on the rules of a game, which may become a social liability. Likewise, a child with ADHD in the absence of ASD may be so distractible that focusing on what other kids are saying and their paired facial expressions is compromised, leading to poor-quality social reciprocity during interactions with peers. Given the remarkable overlap in shared symptoms, it is essential for pediatric providers to consider Tourette syndrome in the differential for any child with repetitive movements and behaviors in addition to ASD and a wide array of other neurodevelopment differences, including global developmental delays and intellectual disabilities. This is of particular importance as the diagnosis of Tourette syndrome can be used to gain access to developmental disability services if the condition has resulted in true adaptive impairments.

It is determined that the boy does in fact meet criteria for ADHD, but also for OCD and Tourette syndrome. Both his Autism Diagnostic Observation Schedule and DSM-5–influenced autism interview are found to be in the nonclinical ranges, given his quality of communication, social engagement, imaginative play, and varied interests. A diagnosis of ASD is not felt to be an appropriate conceptualization of his neurodevelopmental differences. He is started on a low dose of guanfacine, which induces a decline in tics, impulsivity, and hyperkinesis. He is given a 504 plan in school that includes scheduled “tic breaks,” sensory fidgets for use in the classroom, extra movement opportunities as needed, and utilization of a gentle cueing system between him and his teacher for low-key redirection of disruptive behaviors. He is no longer penalized for inattention or tics, and his 504 plan protects him from the use of recess removal as a behavioral modification strategy.

His parents enroll him in the community swim program for extra exercise, focus on decreasing screen time, and give him an earlier bedtime to help decrease his tics and rigidities, while improving his ability to self-regulate. Eventually, a low dose of a newer-generation stimulant is added to his guanfacine, with excellent results and only a mild increase in tolerable tics.

The child in the vignette did well with a 504 plan based on his medical diagnoses, though if related learning difficulties had persisted, eligibility under Other Health Impaired could be used to provide eligibility for an Individualized Education Plan. Alpha-agonists can be helpful for symptom control in those with Tourette syndrome by simultaneously treating tics, hyperkinesis, and impulsivity, while decreasing the risk of tic exacerbation with use of stimulants. Overall, understanding the neurodiversity related to Tourette syndrome can help providers advocate for home and community-based supports to optimize general functioning and quality of life.

Dr. Roth is a developmental and behavioral pediatrician in Eugene, Ore. She has no conflicts of interest.

References

Darrow S et al. J Am Acad Child Adolescent Psych. 2017;56(7):610-7.

AAP Section on Developmental and Behavioral Pediatrics. Developmental and Behavioral Pediatrics. Voigt RG et al, eds. 2018: American Academy of Pediatrics.

Tourette syndrome, attention-deficit/hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), and autism spectrum disorder (ASD) share significant overlap in symptomatology, and it can be challenging at times to distinguish between these conditions. Being able to do so, however, can help guide more targeted interventions and accommodations to optimize a patient’s level of functioning.

Oregon Health &amp; Science University (OHSU)

Case example

A healthy, bright 6-year-old boy is referred by his family doctor to an academic medical center for a full team evaluation because of suspicion of ASD, after having already been diagnosed with ADHD at the age of 5. His difficulties with inattention, impulsivity, and hyperactivity, as well as his behavioral rigidities and sensory avoidant and sensory seeking behaviors have caused functional impairments for him in his kindergarten classroom. He has been penalized with removal of recess on more than one occasion. A low dose of a stimulant had been tried but resulted in a perceived increase in disruptive behaviors.

The boy, while hyperkinetic and often paying poor attention, is quite capable of high-quality and well-modulated eye contact paired with typical social referencing and reciprocity when actively engaging with the examiner and his parents. He does have a reported history of serial fixated interests and some repetitive behaviors but is also noted to be flexible in his interpersonal style, maintains other varied and typical interests, easily directs affect, utilizes a wide array of fluid gestures paired naturally with verbal communication, and shares enjoyment with smoothly coordinated gaze. He has mild articulation errors but uses pronouns appropriately and has no scripted speech or echolalia, though does engage in some whispered palilalia intermittently.

He is generally quite cooperative and redirectable when focused and has a completely normal physical and neurologic examination. During the visit, the doctor notices the boy making an intermittent honking sound, which parents report as an attention-seeking strategy during times of stress. Further physician-guided information gathering around other repetitive noises and movements elicits a history of engagement in repetitive hand-to-groin movements, some exaggerated blinking, and a number of other waxing and waning subtle motor and phonic tics with onset in preschool. These noises and movements have generally been identified as “fidgeting” and “misbehaving” by well-meaning caregivers in the home and school environments.

Both Tourette syndrome and ASD are more common in males, with stereotyped patterns of movements and behaviors; anxious, obsessive, and compulsive behaviors resulting in behavioral rigidities; sensory sensitivities; and increased rates of hyperkinesis with decreased impulse control which result in increased sensory-seeking behaviors. Diagnostic criteria for Tourette syndrome are met when a child has had multiple motor tics and at least one phonic tic present for at least 1 year, with tic-free intervals lasting no longer than 3 months, and with onset before the age of 18. Typically, tics emerge in late preschool and early grade school, and some children even develop repetitive movements as early as toddlerhood. Tics tend to worsen around the peripubertal era, then often generally improve in the teen years. Tic types, frequency, and severity general fluctuate over time.

Forty percent of children with Tourette syndrome also meet criteria for OCD, with many more having OCD traits, and about 65% of children with Tourette syndrome also meet criteria for ADHD, with many more having ADHD traits. OCD can lead to more rigid and directive social interactions in children as well as obsessive interests, just as ADHD can lead to less socially attuned and less cooperative behaviors, even in children who do not meet criteria for ASD.

For example, a child with OCD in the absence of ASD may still “police” other kids in class and be overly focused on the rules of a game, which may become a social liability. Likewise, a child with ADHD in the absence of ASD may be so distractible that focusing on what other kids are saying and their paired facial expressions is compromised, leading to poor-quality social reciprocity during interactions with peers. Given the remarkable overlap in shared symptoms, it is essential for pediatric providers to consider Tourette syndrome in the differential for any child with repetitive movements and behaviors in addition to ASD and a wide array of other neurodevelopment differences, including global developmental delays and intellectual disabilities. This is of particular importance as the diagnosis of Tourette syndrome can be used to gain access to developmental disability services if the condition has resulted in true adaptive impairments.

It is determined that the boy does in fact meet criteria for ADHD, but also for OCD and Tourette syndrome. Both his Autism Diagnostic Observation Schedule and DSM-5–influenced autism interview are found to be in the nonclinical ranges, given his quality of communication, social engagement, imaginative play, and varied interests. A diagnosis of ASD is not felt to be an appropriate conceptualization of his neurodevelopmental differences. He is started on a low dose of guanfacine, which induces a decline in tics, impulsivity, and hyperkinesis. He is given a 504 plan in school that includes scheduled “tic breaks,” sensory fidgets for use in the classroom, extra movement opportunities as needed, and utilization of a gentle cueing system between him and his teacher for low-key redirection of disruptive behaviors. He is no longer penalized for inattention or tics, and his 504 plan protects him from the use of recess removal as a behavioral modification strategy.

His parents enroll him in the community swim program for extra exercise, focus on decreasing screen time, and give him an earlier bedtime to help decrease his tics and rigidities, while improving his ability to self-regulate. Eventually, a low dose of a newer-generation stimulant is added to his guanfacine, with excellent results and only a mild increase in tolerable tics.

The child in the vignette did well with a 504 plan based on his medical diagnoses, though if related learning difficulties had persisted, eligibility under Other Health Impaired could be used to provide eligibility for an Individualized Education Plan. Alpha-agonists can be helpful for symptom control in those with Tourette syndrome by simultaneously treating tics, hyperkinesis, and impulsivity, while decreasing the risk of tic exacerbation with use of stimulants. Overall, understanding the neurodiversity related to Tourette syndrome can help providers advocate for home and community-based supports to optimize general functioning and quality of life.

Dr. Roth is a developmental and behavioral pediatrician in Eugene, Ore. She has no conflicts of interest.

References

Darrow S et al. J Am Acad Child Adolescent Psych. 2017;56(7):610-7.

AAP Section on Developmental and Behavioral Pediatrics. Developmental and Behavioral Pediatrics. Voigt RG et al, eds. 2018: American Academy of Pediatrics.

Tourette syndrome, attention-deficit/hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), and autism spectrum disorder (ASD) share significant overlap in symptomatology, and it can be challenging at times to distinguish between these conditions. Being able to do so, however, can help guide more targeted interventions and accommodations to optimize a patient’s level of functioning.

Oregon Health &amp; Science University (OHSU)

Case example

A healthy, bright 6-year-old boy is referred by his family doctor to an academic medical center for a full team evaluation because of suspicion of ASD, after having already been diagnosed with ADHD at the age of 5. His difficulties with inattention, impulsivity, and hyperactivity, as well as his behavioral rigidities and sensory avoidant and sensory seeking behaviors have caused functional impairments for him in his kindergarten classroom. He has been penalized with removal of recess on more than one occasion. A low dose of a stimulant had been tried but resulted in a perceived increase in disruptive behaviors.

The boy, while hyperkinetic and often paying poor attention, is quite capable of high-quality and well-modulated eye contact paired with typical social referencing and reciprocity when actively engaging with the examiner and his parents. He does have a reported history of serial fixated interests and some repetitive behaviors but is also noted to be flexible in his interpersonal style, maintains other varied and typical interests, easily directs affect, utilizes a wide array of fluid gestures paired naturally with verbal communication, and shares enjoyment with smoothly coordinated gaze. He has mild articulation errors but uses pronouns appropriately and has no scripted speech or echolalia, though does engage in some whispered palilalia intermittently.

He is generally quite cooperative and redirectable when focused and has a completely normal physical and neurologic examination. During the visit, the doctor notices the boy making an intermittent honking sound, which parents report as an attention-seeking strategy during times of stress. Further physician-guided information gathering around other repetitive noises and movements elicits a history of engagement in repetitive hand-to-groin movements, some exaggerated blinking, and a number of other waxing and waning subtle motor and phonic tics with onset in preschool. These noises and movements have generally been identified as “fidgeting” and “misbehaving” by well-meaning caregivers in the home and school environments.

Both Tourette syndrome and ASD are more common in males, with stereotyped patterns of movements and behaviors; anxious, obsessive, and compulsive behaviors resulting in behavioral rigidities; sensory sensitivities; and increased rates of hyperkinesis with decreased impulse control which result in increased sensory-seeking behaviors. Diagnostic criteria for Tourette syndrome are met when a child has had multiple motor tics and at least one phonic tic present for at least 1 year, with tic-free intervals lasting no longer than 3 months, and with onset before the age of 18. Typically, tics emerge in late preschool and early grade school, and some children even develop repetitive movements as early as toddlerhood. Tics tend to worsen around the peripubertal era, then often generally improve in the teen years. Tic types, frequency, and severity general fluctuate over time.

Forty percent of children with Tourette syndrome also meet criteria for OCD, with many more having OCD traits, and about 65% of children with Tourette syndrome also meet criteria for ADHD, with many more having ADHD traits. OCD can lead to more rigid and directive social interactions in children as well as obsessive interests, just as ADHD can lead to less socially attuned and less cooperative behaviors, even in children who do not meet criteria for ASD.

For example, a child with OCD in the absence of ASD may still “police” other kids in class and be overly focused on the rules of a game, which may become a social liability. Likewise, a child with ADHD in the absence of ASD may be so distractible that focusing on what other kids are saying and their paired facial expressions is compromised, leading to poor-quality social reciprocity during interactions with peers. Given the remarkable overlap in shared symptoms, it is essential for pediatric providers to consider Tourette syndrome in the differential for any child with repetitive movements and behaviors in addition to ASD and a wide array of other neurodevelopment differences, including global developmental delays and intellectual disabilities. This is of particular importance as the diagnosis of Tourette syndrome can be used to gain access to developmental disability services if the condition has resulted in true adaptive impairments.

It is determined that the boy does in fact meet criteria for ADHD, but also for OCD and Tourette syndrome. Both his Autism Diagnostic Observation Schedule and DSM-5–influenced autism interview are found to be in the nonclinical ranges, given his quality of communication, social engagement, imaginative play, and varied interests. A diagnosis of ASD is not felt to be an appropriate conceptualization of his neurodevelopmental differences. He is started on a low dose of guanfacine, which induces a decline in tics, impulsivity, and hyperkinesis. He is given a 504 plan in school that includes scheduled “tic breaks,” sensory fidgets for use in the classroom, extra movement opportunities as needed, and utilization of a gentle cueing system between him and his teacher for low-key redirection of disruptive behaviors. He is no longer penalized for inattention or tics, and his 504 plan protects him from the use of recess removal as a behavioral modification strategy.

His parents enroll him in the community swim program for extra exercise, focus on decreasing screen time, and give him an earlier bedtime to help decrease his tics and rigidities, while improving his ability to self-regulate. Eventually, a low dose of a newer-generation stimulant is added to his guanfacine, with excellent results and only a mild increase in tolerable tics.

The child in the vignette did well with a 504 plan based on his medical diagnoses, though if related learning difficulties had persisted, eligibility under Other Health Impaired could be used to provide eligibility for an Individualized Education Plan. Alpha-agonists can be helpful for symptom control in those with Tourette syndrome by simultaneously treating tics, hyperkinesis, and impulsivity, while decreasing the risk of tic exacerbation with use of stimulants. Overall, understanding the neurodiversity related to Tourette syndrome can help providers advocate for home and community-based supports to optimize general functioning and quality of life.

Dr. Roth is a developmental and behavioral pediatrician in Eugene, Ore. She has no conflicts of interest.

References

Darrow S et al. J Am Acad Child Adolescent Psych. 2017;56(7):610-7.

AAP Section on Developmental and Behavioral Pediatrics. Developmental and Behavioral Pediatrics. Voigt RG et al, eds. 2018: American Academy of Pediatrics.

Sanfilippo syndrome is a rare inherited neurodegenerative metabolic disorder for which there are no approved therapies. Symptoms of the more severe subtypes typically begin within the first years of life, rapidly producing serious and progressive physical and cognitive deficits. The underlying pathophysiology is targetable, but the delay in diagnosis of this as well as other lysosomal storage disorders (LSDs) is slowing progress toward effective therapies.

“Lack of awareness and the delays to diagnosis have been a real challenge for us. There is reason for cautious optimism about treatments now in or approaching clinical studies, but to evaluate efficacy on cognitive outcomes we need to enroll more children at a very young age, before loss of milestones,” according to Cara O’Neill, MD, a co-founder and chief science officer of Cure Sanfilippo Foundation.

Epidemiology and description

Sanfilippo syndrome, like the more than 50 other LSDs, is caused by a gene mutation that leads to an enzyme deficiency in the lysosome.¹ In the case of Sanfilippo syndrome, also known as mucopolysaccharidosis (MPS III), there are hundreds of mutations that can lead to Sanfilippo by altering the function of one of the four genes essential to degradation of heparan sulfate.² Lysosomal accumulation of heparan sulfate drives a broad spectrum of progressive and largely irreversible symptoms that typically begin with somatic manifestations, such as bowel dysfunction and recurrent ear and upper respiratory infections.

Impairment of the central nervous system (CNS) usually occurs early in life, halting physical and mental development. As it progresses, accumulation of heparan sulfate in a variety of cells leads to a cascade of abnormal cellular signaling and dysfunction. Disruption of these processes, which are critical for normal neurodevelopment, result in loss of the developmental skills already gained and eventually loss of brain tissue.³ Although life expectancy has improved with supportive care, survival into adulthood is typically limited to milder forms.⁴

Over the past several years, progress in this and other LSDs has yielded therapeutic targets, including those involving gene repair and enzyme replacement. Already approved for use in some LSDs, these therapies have also shown promise in the experimental setting for Sanfilippo syndrome, leading to several completed clinical trials.⁵

So far, none of these treatments has advanced beyond clinical trials in Sanfilippo syndrome, but there have been favorable changes in the markers of disease, suggesting that better methods of treatment delivery and/or more sensitive tools to measure clinical change might lead to evidence of disease attenuation. However, the promise of treatment in all cases has been to prevent, slow, or halt progression, not to reverse it. This point is important, because it indicates that degree of benefit will depend on enrolling patients early in life. Even if effective therapies are identified, few patients will benefit without strategies to accelerate diagnosis.

In fact, “one study⁶ reported that the average age of diagnosis for Sanfilippo syndrome has not improved over the past 30 years,” according to Dr. O’Neill. She indicated that this has been frustrating, given the availability of clinical trials on which progress is dependent. There is no widely accepted protocol for who and when to test for Sanfilippo syndrome or other LSDs, but Dr. O’Neill’s organization is among those advocating for strategies to detect these diseases earlier, including screening at birth.

Almost by definition, the clinical diagnosis of rare diseases poses a challenge. With nonspecific symptoms and a broad range of potential diagnoses, diseases with a low incidence are not the first ones that are typically considered. In the case of Sanfilippo syndrome, published studies indicate incidence rates at or below 1 per 70,000 live births.⁷ However, the incidence rates have been highly variable not only by geographical regions but even across neighboring countries where genetic risk would be expected to be similar.

In Europe, for example, epidemiologic studies suggest the lifetime risk of MPS IIIA is approximately two times greater in Germany and the Netherlands relative to France and Sweden.⁷ It is possible that the methodology for identifying cases might be a more important factor than differences in genetic risk to explain this variability. Many experts, including Dr. O’Neill, believe that prevalence figures for Sanfilippo syndrome are typically underestimates because of the frequency with which LSDs are attributed to other pathology.

“For these types of rare disorders, a clinician might only see a single case over a career, and the symptoms can vary in presentation and severity with many alternatives to consider in the differential diagnosis,” Dr. O’Neill explained. She cited case reports in which symptoms of Sanfilippo syndrome after a period of initial normal development has been initially attributed to autism, which is a comorbid feature of the disease, idiopathic developmental delay, or other nonprogressive disorders until further clinical deterioration leads to additional testing. The implication is that LSDs must be considered far earlier despite their rarity.

For the least common of the four clinical subtypes, MPS IIIC and MPS IIID, the median ages of diagnosis have ranged from 4.5 to 19 years of age.⁷ This is likely a reflection of a slower progression and a later onset of clinical manifestations.

For the more rapidly progressing and typically more severe subtypes, MPS IIIA and MPS IIIB, the diagnosis is typically made earlier. In one review of epidemiologic studies in different countries, the earliest reported median age at diagnosis was 2.5 years,⁷ a point at which significant disease progression is likely to have already occurred. If the promise of treatments in development is prevention of disease progression, disability in many patients might be substantial if the time to diagnosis is not reduced.

Screening and testing

Independent of the potential to enroll children in clinical trials, early diagnosis also advances the opportunities for supportive care to lessen the burden of the disease on patients and families. Perhaps even more important, early diagnosis is vital to family planning. Since the American pediatrician Sylvester Sanfilippo, MD, first described this syndrome in 1963,⁷ the genetic profile and many of the features of the disease have become well characterized.⁸

Diagnosis: Signs and symptoms

Despite the differences in progression of the MPS III subtypes, the clinical characteristics are more similar than different. In all patients, prenatal and infant development are typically normal. The initial signs of disease can be found in the newborn, such as neonatal tachypnea, through the early infancy period, such as macrocephaly. However, these are not commonly recognized until about age 1 or soon after in those with MPS IIIA and IIIB.³ Speech delay is the first developmental delay seen in most patients. In those with MPS IIIC, initial symptoms are typically detected at age 3 or later and progress more slowly.^10,11 The same is likely to be true of MPS IIID, although this subtype is less well characterized than the other three.⁷

Although many organs can be involved, degeneration of the CNS is regarded as the most characteristic.³ In aggressive disease, this includes slower acquisition of and failure to meet developmental milestones with progressive intellectual disability, while behavioral difficulties are a more common initial compliant in children with milder disease.^13,14 These behavioral changes include hyperactivity, inattention, autistic behaviors, worsening safety awareness, and in some cases aggressive behavior that can be destructive. Sleep disturbances are common.¹⁵Because of variability inherent in descriptions of relatively small numbers of patients, the characterization of each of the MPS III subgroups is based on a limited number of small studies, but most patients demonstrate behavior disorders, have coarse facial features, and develop speech delay, according to a survey conducted of published studies.⁷ Collectively, abnormal behavior was identified as an early symptom in 77% of those with MPS IIIA, 69% of those with IIIB, and 77% of those with IIIC.

For MPS IIIA, loss of speech was observed at a median age of 3.8 years and loss of walking ability at 10.4 years. The median survival has been reported to range between 13 and 18 years. In children with MPS IIIB, the median age of speech loss was reported to about the same age, while loss of walking ability occurred at 11 years. In one study of MPS IIIB, 24% of patients had developed dementia by age 6 years, and the reported median survival has ranged between 17 and 19 years. For MPS IIIC, the onset of clinical symptoms has been observed at a median age of 3.5 years with evidence of cognitive loss observed in 33% of children by the age of 6 years. The median survival has ranged from 19 to 34 years in three studies tracing the natural history of this MPS III subtype.

The differential diagnosis reasonably includes other types of mucopolysaccharidosis disorders with cognitive impairment, including Hurler, Hunter, or Sly syndromes, other neurodevelopmental disorders, and inborn errors of metabolism. The heterogeneity of the features makes definitive laboratory or genetic testing, rather than the effort to differentiate clinical features, appropriate for a definitive diagnosis.

Once the diagnosis is made, other examinations for the common complications of Sanfilippo syndrome are appropriate. Abdominal imaging is appropriate for detecting complications in the gastrointestinal tract, including hepatomegaly, which has been reported in more than half of patients with MPS IIIA and IIIB and in 39% of patients with IIIC.⁷ In patients with breathing concerns at night and/or sleep disturbance, polysomnography can be useful for identifying sleep apnea and nocturnal seizure activity. In children suspected of seizures, EEG is appropriate. In one study, 66% of patients with MPS IIIA developed seizure activity.¹⁶ This has been less commonly reported in MPS IIIB and IIIC, ranging from 8% to 13%.¹⁵

Formal hearing evaluation is indicated for any child with speech delays. Hearing loss typically develops after the newborn period in Sanfilippo and may affect peak language acquisition if not treated, according to Dr. O’Neill.

Radiographic studies for dysostosis multiplex or other skeletal abnormalities are also appropriate based on clinical presentation.

Treatment: Present and future

In the absence of treatments to improve the prognosis of Sanfilippo syndrome, current management is based on supportive care and managing organ-specific complications. However, several strategies have proven viable in experimental models and led to clinical trials. None of these therapies has reached approval yet, but several have been associated with attenuation of biomarkers of MPS III disease activity.

Of nearly 30 Sanfilippo clinical trials conducted over the past 20 years, at least 9 have now been completed.⁵ In addition to studying gene therapy and enzyme replacement therapy, these trials have included stem cell transplantation and substrate reduction therapy, for which the goal is to reduce synthesis of the heparan sulfate GAG to prevent accumulation.⁵ Of this latter approach, promising initial results with genistein, an isoflavone that breaks down heparan sulfate, reached a phase 3 evaluation.¹⁸ Although heparan sulfate levels in the CNS were non-significantly reduced over the course of the trial, the reduction was not sufficient to attenuate cognitive decline.

In other LSDs, several forms of enzyme replacement therapy are now approved. In Fabry disease, for example, recombinant alpha-galactosidase A has now been used for more than 15 years.¹⁹ Clinical benefit has not yet been demonstrated in patients with Sanfilippo syndrome because of the difficulty of delivering these therapies past the blood-brain barrier. Several strategies have been pursued. For example, intrathecal delivery of recombinant heparan-N-sulfatase reduced CNS levels of GAG heparan sulfate in one phase 2B study, but it approached but fell short of the statistical significance for the primary endpoint of predefined cognitive stabilization.²⁰ The signal of activity and generally acceptable tolerability has encouraged further study, including an ongoing study with promising interim results of intracerebroventricular enzyme replacement in MPS IIIB, according to Dr. O’Neill.

Acceptable safety and promising activity on disease biomarkers have also been seen with gene therapy in clinical trials. In one study that showed attenuation of brain atrophy, there was moderate improvement in behavior and sleep in three of the four patients enrolled.²¹ Other studies using various strategies for gene delivery have also produced signals of activity against the underlying pathology, generating persistent interest in ongoing and planned clinical studies with this form of treatment.²²Unmodified hematopoietic stem cell transplantation (HSCT), an approach that has demonstrated efficacy when delivered early in the course of other LSDs, such as Hurler syndrome,²³ has not yet been associated with significant activity in clinical studies of MPS III, including those that initiated treatment prior to the onset of neurological symptoms.²⁴ However, promising early results have been reported in a study of gene-modified HSCT, which overexpresses the MPS IIIA enzyme.

“The clinical trial landscape fluctuates quite a bit, so I always encourage clinicians and families to check back often for updates. Patient organizations can also be helpful for understanding the most up-to-date and emerging trial options,” Dr. O’Neill reported.

Although it is expected that the greatest benefit would be derived from treatments initiated before or very early after the onset of symptoms, based on the limited potential for reversing cognitive loss, Dr. O’Neill said that she and others are also striving to offer treatments for individuals now living with Sanfilippo syndrome.

“We have to be willing to test treatments that are symptomatic in nature. To that aim, the Cure Sanfilippo Foundation has sponsored a study of a CNS-penetrating anti-inflammatory agent in advanced-disease patients more than 4 years of age,” Dr. O’Neill said. This group of patients typically been ineligible for clinical trials in the past. Dr. O’Neill hopes to change this orientation.

“It is important to highlight that all patients deserve our efforts to improve their quality of life and alleviate suffering, regardless of how old they are or how progressed in the disease they happen to be,” she said.

However, whether the goal is enrollment before or early in disease or later in disease progression, the challenge of enrolling sufficient numbers of patients to confirm clinical activity has been and continues to be a hurdle to progress.

“Clinical studies in Sanfilippo enroll relatively small numbers of patients, often 20 or less,” said Dr. O’Neill, explaining one of the reasons why her organization has been so active in raising awareness and funding such studies. For patients and families, the Cure Sanfilippo Foundation can offer a variety of guidance and support, but information about opportunities for clinical trial participation is a key resource they provide for families and their physicians.
 

Conclusion

For most children with Sanfilippo syndrome, life expectancy is limited. However, the characterization of the genetic causes and the biochemistry of the subtypes has led to several viable therapeutic approaches under development. There has been progress in delivery of therapeutic enzymes to the CNS, and there is substantial optimism that more progress is coming. One issue for treatment development, is the last of a clear regulatory pathway addressing important biomarkers of pathology, such as heparan sulfate burden. Developing treatments that address this issue or impaired enzyme activity levels have promise for preventing progression, particularly if started in infancy. However, the effort to draw awareness to this disease is the first step toward accelerating the time to an early diagnosis and subsequent opportunities to enroll in clinical trials.

References

1. Sun A. Lysosomal storage disease overview. Ann Transl Med. 2018 Dec;6(24):476. doi: 10.21037/atm.2018.11.39.

2. Andrade F et al. Sanfilippo syndrome: Overall review. Pediatr Int. 2015 Jun;57(3):331-8. doi: 10.1111/ped.12636.

3. Fedele AO. Sanfilippo syndrome: Causes, consequences, and treatments. Appl Clin Genet. 2015 Nov 25;8:269-81. doi: 10.2147/TACG.S57672.

4. Lavery C et al. Mortality in patients with Sanfilippo syndrome. Orphanet J Rare Dis. 2017 Oct 23;12(1):168. doi: 10.1186/s13023-017-0717-y.

5. Pearse Y et al. A cure for Sanfilippo syndrome? A summary of current therapeutic approaches and their promise. Med Res Arch. 2020 Feb 1;8(2). doi: 10.18103/mra.v8i2.2045.

6. Kuiper GA et al. Failure to shorten the diagnostic delay in two ultrao-rphan diseases (mucopolysaccharidosis types I and III): potential causes and implication. Orphanet J Rare Dis. 2018;13:2. Doi: 10.1186/s13023-017-0733-y.

7. Zelei T et al. Epidemiology of Sanfilippo syndrome: Results of a systematic literature review. Orphanet J Rare Dis. 2018 Apr 10;13(1):53. doi: 10.1186/s13023-018-0796-4.

8. Wagner VF, Northrup H. Mucopolysaccaharidosis type III. Gene Reviews. 2019 Sep 19. University of Washington, Seattle. https://www.ncbi.nlm.nih.gov/books/NBK546574/8.

9. O’Neill C et al. Natural history of facial features observed in Sanfilippo syndrome (MPS IIIB) using a next generation phenotyping tool. Mol Genet Metab. 2019 Feb;126:S112.

10. Ruijter GJ et al. Clinical and genetic spectrum of Sanfilippo type C (MPS IIIC) disease in the Netherlands. Mol Genet Metab. 2008 Feb;93(2):104-11. doi: 10.1016/j.ymgme.2007.09.011.

11. Valstar MJ et al. Mucopolysaccharidosis type IIID: 12 new patients and 15 novel mutations. Hum Mutat. 2010 May;31(5):E1348-60. doi: 10.1002/humu.21234.

12. Nijmeijer SCM. The attenuated end of phenotypic spectrum in MPS III: from late-onset stable cognitive impairment to non-neuronopathic phenotype. Orphanet J Rare Dis. 2019;14:249. Doi10.1186/s13023-019-1232-0.

13. Nidiffer FD, Kelly TE. Developmental and degenerative patterns associated with cognitive, behavioural and motor difficulties in the Sanfilippo syndrome: An epidemiological study. J Ment Defic Res. 1983 Sep;27 (Pt 3):185-203. doi: 10.1111/j.1365-2788.1983.tb00291.x.

14. Bax MC, Colville GA. Behaviour in mucopolysaccharide disorders. Arch Dis Child. 1995 Jul;73(1):77-81. doi: 10.1136/adc.73.1.77.

15. Fraser J et al. Sleep disturbance in mucopolysaccharidosis type III (Sanfilippo syndrome): A survey of managing clinicians. Clin Genet. 2002 Nov;62(5):418-21. doi: 10.1034/j.1399-0004.2002.620512.x.

16. Valstar MJ et al. Mucopolysaccharidosis type IIIA: Clinical spectrum and genotype-phenotype correlations. Ann Neurol. 2010 Dec;68(6):876-87. doi: 10.1002/ana.22092.

17. Heron B et al. Incidence and natural history of mucopolysaccharidosis type III in France and comparison with United Kingdom and Greece. Am J Med Genet A. 2011 Jan;155A(1):58-68. doi: 10.1002/ajmg.a.33779.

18. Delgadillo V et al. Genistein supplementation in patients affected by Sanfilippo disease. J Inherit Metab Dis. 2011 Oct;34(5):1039-44. doi: 10.1007/s10545-011-9342-4.

19. van der Veen SJ et al. Developments in the treatment of Fabry disease. J Inherit Metab Dis. 2020 Sep;43(5):908-21. doi: 10.1002/jimd.12228.

20. Wijburg FA et al. Intrathecal heparan-N-sulfatase in patients with Sanfilippo syndrome type A: A phase IIb randomized trial. Mol Genet Metab. 2019 Feb;126(2):121-30. doi: 10.1016/j.ymgme.2018.10.006.

21. Tardieu M et al. Intracerebral administration of adeno-associated viral vector serotype rh.10 carrying human SGSH and SUMF1 cDNAs in children with mucopolysaccharidosis type IIIA disease: Results of a phase I/II trial. Hum Gene Ther. 2014 Jun;25(6):506-16. doi: 10.1089/hum.2013.238.

22. Marco S et al. In vivo gene therapy for mucopolysaccharidosis type III (Sanfilippo syndrome): A new treatment horizon. Hum Gene Ther. 2019 Oct;30(10):1211-1121. doi: 10.1089/hum.2019.217.

23. Taylor M et al. Hematopoietic stem cell transplantation for mucopolysaccharidoses: Past, present, and future. Biol Blood Marrow Transplant. 2019 Jul;25(7):e226-e246. doi: 10.1016/j.bbmt.2019.02.012.

24. Sivakumur P, Wraith JE. Bone marrow transplantation in mucopolysaccharidosis type IIIA: A comparison of an early treated patient with his untreated sibling. J Inherit Metab Dis. 1999 Oct;22(7):849-50. doi: 10.1023/a:1005526628598.

Sanfilippo syndrome is a rare inherited neurodegenerative metabolic disorder for which there are no approved therapies. Symptoms of the more severe subtypes typically begin within the first years of life, rapidly producing serious and progressive physical and cognitive deficits. The underlying pathophysiology is targetable, but the delay in diagnosis of this as well as other lysosomal storage disorders (LSDs) is slowing progress toward effective therapies.

“Lack of awareness and the delays to diagnosis have been a real challenge for us. There is reason for cautious optimism about treatments now in or approaching clinical studies, but to evaluate efficacy on cognitive outcomes we need to enroll more children at a very young age, before loss of milestones,” according to Cara O’Neill, MD, a co-founder and chief science officer of Cure Sanfilippo Foundation.

Epidemiology and description

Sanfilippo syndrome, like the more than 50 other LSDs, is caused by a gene mutation that leads to an enzyme deficiency in the lysosome.¹ In the case of Sanfilippo syndrome, also known as mucopolysaccharidosis (MPS III), there are hundreds of mutations that can lead to Sanfilippo by altering the function of one of the four genes essential to degradation of heparan sulfate.² Lysosomal accumulation of heparan sulfate drives a broad spectrum of progressive and largely irreversible symptoms that typically begin with somatic manifestations, such as bowel dysfunction and recurrent ear and upper respiratory infections.

Impairment of the central nervous system (CNS) usually occurs early in life, halting physical and mental development. As it progresses, accumulation of heparan sulfate in a variety of cells leads to a cascade of abnormal cellular signaling and dysfunction. Disruption of these processes, which are critical for normal neurodevelopment, result in loss of the developmental skills already gained and eventually loss of brain tissue.³ Although life expectancy has improved with supportive care, survival into adulthood is typically limited to milder forms.⁴

Over the past several years, progress in this and other LSDs has yielded therapeutic targets, including those involving gene repair and enzyme replacement. Already approved for use in some LSDs, these therapies have also shown promise in the experimental setting for Sanfilippo syndrome, leading to several completed clinical trials.⁵

So far, none of these treatments has advanced beyond clinical trials in Sanfilippo syndrome, but there have been favorable changes in the markers of disease, suggesting that better methods of treatment delivery and/or more sensitive tools to measure clinical change might lead to evidence of disease attenuation. However, the promise of treatment in all cases has been to prevent, slow, or halt progression, not to reverse it. This point is important, because it indicates that degree of benefit will depend on enrolling patients early in life. Even if effective therapies are identified, few patients will benefit without strategies to accelerate diagnosis.

In fact, “one study⁶ reported that the average age of diagnosis for Sanfilippo syndrome has not improved over the past 30 years,” according to Dr. O’Neill. She indicated that this has been frustrating, given the availability of clinical trials on which progress is dependent. There is no widely accepted protocol for who and when to test for Sanfilippo syndrome or other LSDs, but Dr. O’Neill’s organization is among those advocating for strategies to detect these diseases earlier, including screening at birth.

Almost by definition, the clinical diagnosis of rare diseases poses a challenge. With nonspecific symptoms and a broad range of potential diagnoses, diseases with a low incidence are not the first ones that are typically considered. In the case of Sanfilippo syndrome, published studies indicate incidence rates at or below 1 per 70,000 live births.⁷ However, the incidence rates have been highly variable not only by geographical regions but even across neighboring countries where genetic risk would be expected to be similar.

In Europe, for example, epidemiologic studies suggest the lifetime risk of MPS IIIA is approximately two times greater in Germany and the Netherlands relative to France and Sweden.⁷ It is possible that the methodology for identifying cases might be a more important factor than differences in genetic risk to explain this variability. Many experts, including Dr. O’Neill, believe that prevalence figures for Sanfilippo syndrome are typically underestimates because of the frequency with which LSDs are attributed to other pathology.

“For these types of rare disorders, a clinician might only see a single case over a career, and the symptoms can vary in presentation and severity with many alternatives to consider in the differential diagnosis,” Dr. O’Neill explained. She cited case reports in which symptoms of Sanfilippo syndrome after a period of initial normal development has been initially attributed to autism, which is a comorbid feature of the disease, idiopathic developmental delay, or other nonprogressive disorders until further clinical deterioration leads to additional testing. The implication is that LSDs must be considered far earlier despite their rarity.

For the least common of the four clinical subtypes, MPS IIIC and MPS IIID, the median ages of diagnosis have ranged from 4.5 to 19 years of age.⁷ This is likely a reflection of a slower progression and a later onset of clinical manifestations.

For the more rapidly progressing and typically more severe subtypes, MPS IIIA and MPS IIIB, the diagnosis is typically made earlier. In one review of epidemiologic studies in different countries, the earliest reported median age at diagnosis was 2.5 years,⁷ a point at which significant disease progression is likely to have already occurred. If the promise of treatments in development is prevention of disease progression, disability in many patients might be substantial if the time to diagnosis is not reduced.

Screening and testing

Independent of the potential to enroll children in clinical trials, early diagnosis also advances the opportunities for supportive care to lessen the burden of the disease on patients and families. Perhaps even more important, early diagnosis is vital to family planning. Since the American pediatrician Sylvester Sanfilippo, MD, first described this syndrome in 1963,⁷ the genetic profile and many of the features of the disease have become well characterized.⁸

Diagnosis: Signs and symptoms

Despite the differences in progression of the MPS III subtypes, the clinical characteristics are more similar than different. In all patients, prenatal and infant development are typically normal. The initial signs of disease can be found in the newborn, such as neonatal tachypnea, through the early infancy period, such as macrocephaly. However, these are not commonly recognized until about age 1 or soon after in those with MPS IIIA and IIIB.³ Speech delay is the first developmental delay seen in most patients. In those with MPS IIIC, initial symptoms are typically detected at age 3 or later and progress more slowly.^10,11 The same is likely to be true of MPS IIID, although this subtype is less well characterized than the other three.⁷

Although many organs can be involved, degeneration of the CNS is regarded as the most characteristic.³ In aggressive disease, this includes slower acquisition of and failure to meet developmental milestones with progressive intellectual disability, while behavioral difficulties are a more common initial compliant in children with milder disease.^13,14 These behavioral changes include hyperactivity, inattention, autistic behaviors, worsening safety awareness, and in some cases aggressive behavior that can be destructive. Sleep disturbances are common.¹⁵Because of variability inherent in descriptions of relatively small numbers of patients, the characterization of each of the MPS III subgroups is based on a limited number of small studies, but most patients demonstrate behavior disorders, have coarse facial features, and develop speech delay, according to a survey conducted of published studies.⁷ Collectively, abnormal behavior was identified as an early symptom in 77% of those with MPS IIIA, 69% of those with IIIB, and 77% of those with IIIC.

For MPS IIIA, loss of speech was observed at a median age of 3.8 years and loss of walking ability at 10.4 years. The median survival has been reported to range between 13 and 18 years. In children with MPS IIIB, the median age of speech loss was reported to about the same age, while loss of walking ability occurred at 11 years. In one study of MPS IIIB, 24% of patients had developed dementia by age 6 years, and the reported median survival has ranged between 17 and 19 years. For MPS IIIC, the onset of clinical symptoms has been observed at a median age of 3.5 years with evidence of cognitive loss observed in 33% of children by the age of 6 years. The median survival has ranged from 19 to 34 years in three studies tracing the natural history of this MPS III subtype.

The differential diagnosis reasonably includes other types of mucopolysaccharidosis disorders with cognitive impairment, including Hurler, Hunter, or Sly syndromes, other neurodevelopmental disorders, and inborn errors of metabolism. The heterogeneity of the features makes definitive laboratory or genetic testing, rather than the effort to differentiate clinical features, appropriate for a definitive diagnosis.

Once the diagnosis is made, other examinations for the common complications of Sanfilippo syndrome are appropriate. Abdominal imaging is appropriate for detecting complications in the gastrointestinal tract, including hepatomegaly, which has been reported in more than half of patients with MPS IIIA and IIIB and in 39% of patients with IIIC.⁷ In patients with breathing concerns at night and/or sleep disturbance, polysomnography can be useful for identifying sleep apnea and nocturnal seizure activity. In children suspected of seizures, EEG is appropriate. In one study, 66% of patients with MPS IIIA developed seizure activity.¹⁶ This has been less commonly reported in MPS IIIB and IIIC, ranging from 8% to 13%.¹⁵

Formal hearing evaluation is indicated for any child with speech delays. Hearing loss typically develops after the newborn period in Sanfilippo and may affect peak language acquisition if not treated, according to Dr. O’Neill.

Radiographic studies for dysostosis multiplex or other skeletal abnormalities are also appropriate based on clinical presentation.

Treatment: Present and future

In the absence of treatments to improve the prognosis of Sanfilippo syndrome, current management is based on supportive care and managing organ-specific complications. However, several strategies have proven viable in experimental models and led to clinical trials. None of these therapies has reached approval yet, but several have been associated with attenuation of biomarkers of MPS III disease activity.

Of nearly 30 Sanfilippo clinical trials conducted over the past 20 years, at least 9 have now been completed.⁵ In addition to studying gene therapy and enzyme replacement therapy, these trials have included stem cell transplantation and substrate reduction therapy, for which the goal is to reduce synthesis of the heparan sulfate GAG to prevent accumulation.⁵ Of this latter approach, promising initial results with genistein, an isoflavone that breaks down heparan sulfate, reached a phase 3 evaluation.¹⁸ Although heparan sulfate levels in the CNS were non-significantly reduced over the course of the trial, the reduction was not sufficient to attenuate cognitive decline.

In other LSDs, several forms of enzyme replacement therapy are now approved. In Fabry disease, for example, recombinant alpha-galactosidase A has now been used for more than 15 years.¹⁹ Clinical benefit has not yet been demonstrated in patients with Sanfilippo syndrome because of the difficulty of delivering these therapies past the blood-brain barrier. Several strategies have been pursued. For example, intrathecal delivery of recombinant heparan-N-sulfatase reduced CNS levels of GAG heparan sulfate in one phase 2B study, but it approached but fell short of the statistical significance for the primary endpoint of predefined cognitive stabilization.²⁰ The signal of activity and generally acceptable tolerability has encouraged further study, including an ongoing study with promising interim results of intracerebroventricular enzyme replacement in MPS IIIB, according to Dr. O’Neill.

Acceptable safety and promising activity on disease biomarkers have also been seen with gene therapy in clinical trials. In one study that showed attenuation of brain atrophy, there was moderate improvement in behavior and sleep in three of the four patients enrolled.²¹ Other studies using various strategies for gene delivery have also produced signals of activity against the underlying pathology, generating persistent interest in ongoing and planned clinical studies with this form of treatment.²²Unmodified hematopoietic stem cell transplantation (HSCT), an approach that has demonstrated efficacy when delivered early in the course of other LSDs, such as Hurler syndrome,²³ has not yet been associated with significant activity in clinical studies of MPS III, including those that initiated treatment prior to the onset of neurological symptoms.²⁴ However, promising early results have been reported in a study of gene-modified HSCT, which overexpresses the MPS IIIA enzyme.

“The clinical trial landscape fluctuates quite a bit, so I always encourage clinicians and families to check back often for updates. Patient organizations can also be helpful for understanding the most up-to-date and emerging trial options,” Dr. O’Neill reported.

Although it is expected that the greatest benefit would be derived from treatments initiated before or very early after the onset of symptoms, based on the limited potential for reversing cognitive loss, Dr. O’Neill said that she and others are also striving to offer treatments for individuals now living with Sanfilippo syndrome.

“We have to be willing to test treatments that are symptomatic in nature. To that aim, the Cure Sanfilippo Foundation has sponsored a study of a CNS-penetrating anti-inflammatory agent in advanced-disease patients more than 4 years of age,” Dr. O’Neill said. This group of patients typically been ineligible for clinical trials in the past. Dr. O’Neill hopes to change this orientation.

“It is important to highlight that all patients deserve our efforts to improve their quality of life and alleviate suffering, regardless of how old they are or how progressed in the disease they happen to be,” she said.

However, whether the goal is enrollment before or early in disease or later in disease progression, the challenge of enrolling sufficient numbers of patients to confirm clinical activity has been and continues to be a hurdle to progress.

“Clinical studies in Sanfilippo enroll relatively small numbers of patients, often 20 or less,” said Dr. O’Neill, explaining one of the reasons why her organization has been so active in raising awareness and funding such studies. For patients and families, the Cure Sanfilippo Foundation can offer a variety of guidance and support, but information about opportunities for clinical trial participation is a key resource they provide for families and their physicians.
 

Conclusion

For most children with Sanfilippo syndrome, life expectancy is limited. However, the characterization of the genetic causes and the biochemistry of the subtypes has led to several viable therapeutic approaches under development. There has been progress in delivery of therapeutic enzymes to the CNS, and there is substantial optimism that more progress is coming. One issue for treatment development, is the last of a clear regulatory pathway addressing important biomarkers of pathology, such as heparan sulfate burden. Developing treatments that address this issue or impaired enzyme activity levels have promise for preventing progression, particularly if started in infancy. However, the effort to draw awareness to this disease is the first step toward accelerating the time to an early diagnosis and subsequent opportunities to enroll in clinical trials.

References

1. Sun A. Lysosomal storage disease overview. Ann Transl Med. 2018 Dec;6(24):476. doi: 10.21037/atm.2018.11.39.

2. Andrade F et al. Sanfilippo syndrome: Overall review. Pediatr Int. 2015 Jun;57(3):331-8. doi: 10.1111/ped.12636.

3. Fedele AO. Sanfilippo syndrome: Causes, consequences, and treatments. Appl Clin Genet. 2015 Nov 25;8:269-81. doi: 10.2147/TACG.S57672.

4. Lavery C et al. Mortality in patients with Sanfilippo syndrome. Orphanet J Rare Dis. 2017 Oct 23;12(1):168. doi: 10.1186/s13023-017-0717-y.

5. Pearse Y et al. A cure for Sanfilippo syndrome? A summary of current therapeutic approaches and their promise. Med Res Arch. 2020 Feb 1;8(2). doi: 10.18103/mra.v8i2.2045.

6. Kuiper GA et al. Failure to shorten the diagnostic delay in two ultrao-rphan diseases (mucopolysaccharidosis types I and III): potential causes and implication. Orphanet J Rare Dis. 2018;13:2. Doi: 10.1186/s13023-017-0733-y.

7. Zelei T et al. Epidemiology of Sanfilippo syndrome: Results of a systematic literature review. Orphanet J Rare Dis. 2018 Apr 10;13(1):53. doi: 10.1186/s13023-018-0796-4.

8. Wagner VF, Northrup H. Mucopolysaccaharidosis type III. Gene Reviews. 2019 Sep 19. University of Washington, Seattle. https://www.ncbi.nlm.nih.gov/books/NBK546574/8.

9. O’Neill C et al. Natural history of facial features observed in Sanfilippo syndrome (MPS IIIB) using a next generation phenotyping tool. Mol Genet Metab. 2019 Feb;126:S112.

10. Ruijter GJ et al. Clinical and genetic spectrum of Sanfilippo type C (MPS IIIC) disease in the Netherlands. Mol Genet Metab. 2008 Feb;93(2):104-11. doi: 10.1016/j.ymgme.2007.09.011.

11. Valstar MJ et al. Mucopolysaccharidosis type IIID: 12 new patients and 15 novel mutations. Hum Mutat. 2010 May;31(5):E1348-60. doi: 10.1002/humu.21234.

12. Nijmeijer SCM. The attenuated end of phenotypic spectrum in MPS III: from late-onset stable cognitive impairment to non-neuronopathic phenotype. Orphanet J Rare Dis. 2019;14:249. Doi10.1186/s13023-019-1232-0.

13. Nidiffer FD, Kelly TE. Developmental and degenerative patterns associated with cognitive, behavioural and motor difficulties in the Sanfilippo syndrome: An epidemiological study. J Ment Defic Res. 1983 Sep;27 (Pt 3):185-203. doi: 10.1111/j.1365-2788.1983.tb00291.x.

14. Bax MC, Colville GA. Behaviour in mucopolysaccharide disorders. Arch Dis Child. 1995 Jul;73(1):77-81. doi: 10.1136/adc.73.1.77.

15. Fraser J et al. Sleep disturbance in mucopolysaccharidosis type III (Sanfilippo syndrome): A survey of managing clinicians. Clin Genet. 2002 Nov;62(5):418-21. doi: 10.1034/j.1399-0004.2002.620512.x.

16. Valstar MJ et al. Mucopolysaccharidosis type IIIA: Clinical spectrum and genotype-phenotype correlations. Ann Neurol. 2010 Dec;68(6):876-87. doi: 10.1002/ana.22092.

17. Heron B et al. Incidence and natural history of mucopolysaccharidosis type III in France and comparison with United Kingdom and Greece. Am J Med Genet A. 2011 Jan;155A(1):58-68. doi: 10.1002/ajmg.a.33779.

18. Delgadillo V et al. Genistein supplementation in patients affected by Sanfilippo disease. J Inherit Metab Dis. 2011 Oct;34(5):1039-44. doi: 10.1007/s10545-011-9342-4.

19. van der Veen SJ et al. Developments in the treatment of Fabry disease. J Inherit Metab Dis. 2020 Sep;43(5):908-21. doi: 10.1002/jimd.12228.

20. Wijburg FA et al. Intrathecal heparan-N-sulfatase in patients with Sanfilippo syndrome type A: A phase IIb randomized trial. Mol Genet Metab. 2019 Feb;126(2):121-30. doi: 10.1016/j.ymgme.2018.10.006.

21. Tardieu M et al. Intracerebral administration of adeno-associated viral vector serotype rh.10 carrying human SGSH and SUMF1 cDNAs in children with mucopolysaccharidosis type IIIA disease: Results of a phase I/II trial. Hum Gene Ther. 2014 Jun;25(6):506-16. doi: 10.1089/hum.2013.238.

22. Marco S et al. In vivo gene therapy for mucopolysaccharidosis type III (Sanfilippo syndrome): A new treatment horizon. Hum Gene Ther. 2019 Oct;30(10):1211-1121. doi: 10.1089/hum.2019.217.

23. Taylor M et al. Hematopoietic stem cell transplantation for mucopolysaccharidoses: Past, present, and future. Biol Blood Marrow Transplant. 2019 Jul;25(7):e226-e246. doi: 10.1016/j.bbmt.2019.02.012.

24. Sivakumur P, Wraith JE. Bone marrow transplantation in mucopolysaccharidosis type IIIA: A comparison of an early treated patient with his untreated sibling. J Inherit Metab Dis. 1999 Oct;22(7):849-50. doi: 10.1023/a:1005526628598.

Sanfilippo syndrome is a rare inherited neurodegenerative metabolic disorder for which there are no approved therapies. Symptoms of the more severe subtypes typically begin within the first years of life, rapidly producing serious and progressive physical and cognitive deficits. The underlying pathophysiology is targetable, but the delay in diagnosis of this as well as other lysosomal storage disorders (LSDs) is slowing progress toward effective therapies.

“Lack of awareness and the delays to diagnosis have been a real challenge for us. There is reason for cautious optimism about treatments now in or approaching clinical studies, but to evaluate efficacy on cognitive outcomes we need to enroll more children at a very young age, before loss of milestones,” according to Cara O’Neill, MD, a co-founder and chief science officer of Cure Sanfilippo Foundation.

Epidemiology and description

Sanfilippo syndrome, like the more than 50 other LSDs, is caused by a gene mutation that leads to an enzyme deficiency in the lysosome.¹ In the case of Sanfilippo syndrome, also known as mucopolysaccharidosis (MPS III), there are hundreds of mutations that can lead to Sanfilippo by altering the function of one of the four genes essential to degradation of heparan sulfate.² Lysosomal accumulation of heparan sulfate drives a broad spectrum of progressive and largely irreversible symptoms that typically begin with somatic manifestations, such as bowel dysfunction and recurrent ear and upper respiratory infections.

Impairment of the central nervous system (CNS) usually occurs early in life, halting physical and mental development. As it progresses, accumulation of heparan sulfate in a variety of cells leads to a cascade of abnormal cellular signaling and dysfunction. Disruption of these processes, which are critical for normal neurodevelopment, result in loss of the developmental skills already gained and eventually loss of brain tissue.³ Although life expectancy has improved with supportive care, survival into adulthood is typically limited to milder forms.⁴

Over the past several years, progress in this and other LSDs has yielded therapeutic targets, including those involving gene repair and enzyme replacement. Already approved for use in some LSDs, these therapies have also shown promise in the experimental setting for Sanfilippo syndrome, leading to several completed clinical trials.⁵

So far, none of these treatments has advanced beyond clinical trials in Sanfilippo syndrome, but there have been favorable changes in the markers of disease, suggesting that better methods of treatment delivery and/or more sensitive tools to measure clinical change might lead to evidence of disease attenuation. However, the promise of treatment in all cases has been to prevent, slow, or halt progression, not to reverse it. This point is important, because it indicates that degree of benefit will depend on enrolling patients early in life. Even if effective therapies are identified, few patients will benefit without strategies to accelerate diagnosis.

In fact, “one study⁶ reported that the average age of diagnosis for Sanfilippo syndrome has not improved over the past 30 years,” according to Dr. O’Neill. She indicated that this has been frustrating, given the availability of clinical trials on which progress is dependent. There is no widely accepted protocol for who and when to test for Sanfilippo syndrome or other LSDs, but Dr. O’Neill’s organization is among those advocating for strategies to detect these diseases earlier, including screening at birth.

Almost by definition, the clinical diagnosis of rare diseases poses a challenge. With nonspecific symptoms and a broad range of potential diagnoses, diseases with a low incidence are not the first ones that are typically considered. In the case of Sanfilippo syndrome, published studies indicate incidence rates at or below 1 per 70,000 live births.⁷ However, the incidence rates have been highly variable not only by geographical regions but even across neighboring countries where genetic risk would be expected to be similar.

In Europe, for example, epidemiologic studies suggest the lifetime risk of MPS IIIA is approximately two times greater in Germany and the Netherlands relative to France and Sweden.⁷ It is possible that the methodology for identifying cases might be a more important factor than differences in genetic risk to explain this variability. Many experts, including Dr. O’Neill, believe that prevalence figures for Sanfilippo syndrome are typically underestimates because of the frequency with which LSDs are attributed to other pathology.

“For these types of rare disorders, a clinician might only see a single case over a career, and the symptoms can vary in presentation and severity with many alternatives to consider in the differential diagnosis,” Dr. O’Neill explained. She cited case reports in which symptoms of Sanfilippo syndrome after a period of initial normal development has been initially attributed to autism, which is a comorbid feature of the disease, idiopathic developmental delay, or other nonprogressive disorders until further clinical deterioration leads to additional testing. The implication is that LSDs must be considered far earlier despite their rarity.

For the least common of the four clinical subtypes, MPS IIIC and MPS IIID, the median ages of diagnosis have ranged from 4.5 to 19 years of age.⁷ This is likely a reflection of a slower progression and a later onset of clinical manifestations.

For the more rapidly progressing and typically more severe subtypes, MPS IIIA and MPS IIIB, the diagnosis is typically made earlier. In one review of epidemiologic studies in different countries, the earliest reported median age at diagnosis was 2.5 years,⁷ a point at which significant disease progression is likely to have already occurred. If the promise of treatments in development is prevention of disease progression, disability in many patients might be substantial if the time to diagnosis is not reduced.

Screening and testing

Independent of the potential to enroll children in clinical trials, early diagnosis also advances the opportunities for supportive care to lessen the burden of the disease on patients and families. Perhaps even more important, early diagnosis is vital to family planning. Since the American pediatrician Sylvester Sanfilippo, MD, first described this syndrome in 1963,⁷ the genetic profile and many of the features of the disease have become well characterized.⁸

Diagnosis: Signs and symptoms

Despite the differences in progression of the MPS III subtypes, the clinical characteristics are more similar than different. In all patients, prenatal and infant development are typically normal. The initial signs of disease can be found in the newborn, such as neonatal tachypnea, through the early infancy period, such as macrocephaly. However, these are not commonly recognized until about age 1 or soon after in those with MPS IIIA and IIIB.³ Speech delay is the first developmental delay seen in most patients. In those with MPS IIIC, initial symptoms are typically detected at age 3 or later and progress more slowly.^10,11 The same is likely to be true of MPS IIID, although this subtype is less well characterized than the other three.⁷

Although many organs can be involved, degeneration of the CNS is regarded as the most characteristic.³ In aggressive disease, this includes slower acquisition of and failure to meet developmental milestones with progressive intellectual disability, while behavioral difficulties are a more common initial compliant in children with milder disease.^13,14 These behavioral changes include hyperactivity, inattention, autistic behaviors, worsening safety awareness, and in some cases aggressive behavior that can be destructive. Sleep disturbances are common.¹⁵Because of variability inherent in descriptions of relatively small numbers of patients, the characterization of each of the MPS III subgroups is based on a limited number of small studies, but most patients demonstrate behavior disorders, have coarse facial features, and develop speech delay, according to a survey conducted of published studies.⁷ Collectively, abnormal behavior was identified as an early symptom in 77% of those with MPS IIIA, 69% of those with IIIB, and 77% of those with IIIC.

For MPS IIIA, loss of speech was observed at a median age of 3.8 years and loss of walking ability at 10.4 years. The median survival has been reported to range between 13 and 18 years. In children with MPS IIIB, the median age of speech loss was reported to about the same age, while loss of walking ability occurred at 11 years. In one study of MPS IIIB, 24% of patients had developed dementia by age 6 years, and the reported median survival has ranged between 17 and 19 years. For MPS IIIC, the onset of clinical symptoms has been observed at a median age of 3.5 years with evidence of cognitive loss observed in 33% of children by the age of 6 years. The median survival has ranged from 19 to 34 years in three studies tracing the natural history of this MPS III subtype.

The differential diagnosis reasonably includes other types of mucopolysaccharidosis disorders with cognitive impairment, including Hurler, Hunter, or Sly syndromes, other neurodevelopmental disorders, and inborn errors of metabolism. The heterogeneity of the features makes definitive laboratory or genetic testing, rather than the effort to differentiate clinical features, appropriate for a definitive diagnosis.

Once the diagnosis is made, other examinations for the common complications of Sanfilippo syndrome are appropriate. Abdominal imaging is appropriate for detecting complications in the gastrointestinal tract, including hepatomegaly, which has been reported in more than half of patients with MPS IIIA and IIIB and in 39% of patients with IIIC.⁷ In patients with breathing concerns at night and/or sleep disturbance, polysomnography can be useful for identifying sleep apnea and nocturnal seizure activity. In children suspected of seizures, EEG is appropriate. In one study, 66% of patients with MPS IIIA developed seizure activity.¹⁶ This has been less commonly reported in MPS IIIB and IIIC, ranging from 8% to 13%.¹⁵

Formal hearing evaluation is indicated for any child with speech delays. Hearing loss typically develops after the newborn period in Sanfilippo and may affect peak language acquisition if not treated, according to Dr. O’Neill.

Radiographic studies for dysostosis multiplex or other skeletal abnormalities are also appropriate based on clinical presentation.

Treatment: Present and future

In the absence of treatments to improve the prognosis of Sanfilippo syndrome, current management is based on supportive care and managing organ-specific complications. However, several strategies have proven viable in experimental models and led to clinical trials. None of these therapies has reached approval yet, but several have been associated with attenuation of biomarkers of MPS III disease activity.

Of nearly 30 Sanfilippo clinical trials conducted over the past 20 years, at least 9 have now been completed.⁵ In addition to studying gene therapy and enzyme replacement therapy, these trials have included stem cell transplantation and substrate reduction therapy, for which the goal is to reduce synthesis of the heparan sulfate GAG to prevent accumulation.⁵ Of this latter approach, promising initial results with genistein, an isoflavone that breaks down heparan sulfate, reached a phase 3 evaluation.¹⁸ Although heparan sulfate levels in the CNS were non-significantly reduced over the course of the trial, the reduction was not sufficient to attenuate cognitive decline.

In other LSDs, several forms of enzyme replacement therapy are now approved. In Fabry disease, for example, recombinant alpha-galactosidase A has now been used for more than 15 years.¹⁹ Clinical benefit has not yet been demonstrated in patients with Sanfilippo syndrome because of the difficulty of delivering these therapies past the blood-brain barrier. Several strategies have been pursued. For example, intrathecal delivery of recombinant heparan-N-sulfatase reduced CNS levels of GAG heparan sulfate in one phase 2B study, but it approached but fell short of the statistical significance for the primary endpoint of predefined cognitive stabilization.²⁰ The signal of activity and generally acceptable tolerability has encouraged further study, including an ongoing study with promising interim results of intracerebroventricular enzyme replacement in MPS IIIB, according to Dr. O’Neill.

Acceptable safety and promising activity on disease biomarkers have also been seen with gene therapy in clinical trials. In one study that showed attenuation of brain atrophy, there was moderate improvement in behavior and sleep in three of the four patients enrolled.²¹ Other studies using various strategies for gene delivery have also produced signals of activity against the underlying pathology, generating persistent interest in ongoing and planned clinical studies with this form of treatment.²²Unmodified hematopoietic stem cell transplantation (HSCT), an approach that has demonstrated efficacy when delivered early in the course of other LSDs, such as Hurler syndrome,²³ has not yet been associated with significant activity in clinical studies of MPS III, including those that initiated treatment prior to the onset of neurological symptoms.²⁴ However, promising early results have been reported in a study of gene-modified HSCT, which overexpresses the MPS IIIA enzyme.

“The clinical trial landscape fluctuates quite a bit, so I always encourage clinicians and families to check back often for updates. Patient organizations can also be helpful for understanding the most up-to-date and emerging trial options,” Dr. O’Neill reported.

Although it is expected that the greatest benefit would be derived from treatments initiated before or very early after the onset of symptoms, based on the limited potential for reversing cognitive loss, Dr. O’Neill said that she and others are also striving to offer treatments for individuals now living with Sanfilippo syndrome.

“We have to be willing to test treatments that are symptomatic in nature. To that aim, the Cure Sanfilippo Foundation has sponsored a study of a CNS-penetrating anti-inflammatory agent in advanced-disease patients more than 4 years of age,” Dr. O’Neill said. This group of patients typically been ineligible for clinical trials in the past. Dr. O’Neill hopes to change this orientation.

“It is important to highlight that all patients deserve our efforts to improve their quality of life and alleviate suffering, regardless of how old they are or how progressed in the disease they happen to be,” she said.

However, whether the goal is enrollment before or early in disease or later in disease progression, the challenge of enrolling sufficient numbers of patients to confirm clinical activity has been and continues to be a hurdle to progress.

“Clinical studies in Sanfilippo enroll relatively small numbers of patients, often 20 or less,” said Dr. O’Neill, explaining one of the reasons why her organization has been so active in raising awareness and funding such studies. For patients and families, the Cure Sanfilippo Foundation can offer a variety of guidance and support, but information about opportunities for clinical trial participation is a key resource they provide for families and their physicians.
 

Conclusion

For most children with Sanfilippo syndrome, life expectancy is limited. However, the characterization of the genetic causes and the biochemistry of the subtypes has led to several viable therapeutic approaches under development. There has been progress in delivery of therapeutic enzymes to the CNS, and there is substantial optimism that more progress is coming. One issue for treatment development, is the last of a clear regulatory pathway addressing important biomarkers of pathology, such as heparan sulfate burden. Developing treatments that address this issue or impaired enzyme activity levels have promise for preventing progression, particularly if started in infancy. However, the effort to draw awareness to this disease is the first step toward accelerating the time to an early diagnosis and subsequent opportunities to enroll in clinical trials.

References

1. Sun A. Lysosomal storage disease overview. Ann Transl Med. 2018 Dec;6(24):476. doi: 10.21037/atm.2018.11.39.

2. Andrade F et al. Sanfilippo syndrome: Overall review. Pediatr Int. 2015 Jun;57(3):331-8. doi: 10.1111/ped.12636.

3. Fedele AO. Sanfilippo syndrome: Causes, consequences, and treatments. Appl Clin Genet. 2015 Nov 25;8:269-81. doi: 10.2147/TACG.S57672.

4. Lavery C et al. Mortality in patients with Sanfilippo syndrome. Orphanet J Rare Dis. 2017 Oct 23;12(1):168. doi: 10.1186/s13023-017-0717-y.

5. Pearse Y et al. A cure for Sanfilippo syndrome? A summary of current therapeutic approaches and their promise. Med Res Arch. 2020 Feb 1;8(2). doi: 10.18103/mra.v8i2.2045.

6. Kuiper GA et al. Failure to shorten the diagnostic delay in two ultrao-rphan diseases (mucopolysaccharidosis types I and III): potential causes and implication. Orphanet J Rare Dis. 2018;13:2. Doi: 10.1186/s13023-017-0733-y.

7. Zelei T et al. Epidemiology of Sanfilippo syndrome: Results of a systematic literature review. Orphanet J Rare Dis. 2018 Apr 10;13(1):53. doi: 10.1186/s13023-018-0796-4.

8. Wagner VF, Northrup H. Mucopolysaccaharidosis type III. Gene Reviews. 2019 Sep 19. University of Washington, Seattle. https://www.ncbi.nlm.nih.gov/books/NBK546574/8.

9. O’Neill C et al. Natural history of facial features observed in Sanfilippo syndrome (MPS IIIB) using a next generation phenotyping tool. Mol Genet Metab. 2019 Feb;126:S112.

10. Ruijter GJ et al. Clinical and genetic spectrum of Sanfilippo type C (MPS IIIC) disease in the Netherlands. Mol Genet Metab. 2008 Feb;93(2):104-11. doi: 10.1016/j.ymgme.2007.09.011.

11. Valstar MJ et al. Mucopolysaccharidosis type IIID: 12 new patients and 15 novel mutations. Hum Mutat. 2010 May;31(5):E1348-60. doi: 10.1002/humu.21234.

12. Nijmeijer SCM. The attenuated end of phenotypic spectrum in MPS III: from late-onset stable cognitive impairment to non-neuronopathic phenotype. Orphanet J Rare Dis. 2019;14:249. Doi10.1186/s13023-019-1232-0.

13. Nidiffer FD, Kelly TE. Developmental and degenerative patterns associated with cognitive, behavioural and motor difficulties in the Sanfilippo syndrome: An epidemiological study. J Ment Defic Res. 1983 Sep;27 (Pt 3):185-203. doi: 10.1111/j.1365-2788.1983.tb00291.x.

14. Bax MC, Colville GA. Behaviour in mucopolysaccharide disorders. Arch Dis Child. 1995 Jul;73(1):77-81. doi: 10.1136/adc.73.1.77.

15. Fraser J et al. Sleep disturbance in mucopolysaccharidosis type III (Sanfilippo syndrome): A survey of managing clinicians. Clin Genet. 2002 Nov;62(5):418-21. doi: 10.1034/j.1399-0004.2002.620512.x.

16. Valstar MJ et al. Mucopolysaccharidosis type IIIA: Clinical spectrum and genotype-phenotype correlations. Ann Neurol. 2010 Dec;68(6):876-87. doi: 10.1002/ana.22092.

17. Heron B et al. Incidence and natural history of mucopolysaccharidosis type III in France and comparison with United Kingdom and Greece. Am J Med Genet A. 2011 Jan;155A(1):58-68. doi: 10.1002/ajmg.a.33779.

18. Delgadillo V et al. Genistein supplementation in patients affected by Sanfilippo disease. J Inherit Metab Dis. 2011 Oct;34(5):1039-44. doi: 10.1007/s10545-011-9342-4.

19. van der Veen SJ et al. Developments in the treatment of Fabry disease. J Inherit Metab Dis. 2020 Sep;43(5):908-21. doi: 10.1002/jimd.12228.

20. Wijburg FA et al. Intrathecal heparan-N-sulfatase in patients with Sanfilippo syndrome type A: A phase IIb randomized trial. Mol Genet Metab. 2019 Feb;126(2):121-30. doi: 10.1016/j.ymgme.2018.10.006.

21. Tardieu M et al. Intracerebral administration of adeno-associated viral vector serotype rh.10 carrying human SGSH and SUMF1 cDNAs in children with mucopolysaccharidosis type IIIA disease: Results of a phase I/II trial. Hum Gene Ther. 2014 Jun;25(6):506-16. doi: 10.1089/hum.2013.238.

22. Marco S et al. In vivo gene therapy for mucopolysaccharidosis type III (Sanfilippo syndrome): A new treatment horizon. Hum Gene Ther. 2019 Oct;30(10):1211-1121. doi: 10.1089/hum.2019.217.

23. Taylor M et al. Hematopoietic stem cell transplantation for mucopolysaccharidoses: Past, present, and future. Biol Blood Marrow Transplant. 2019 Jul;25(7):e226-e246. doi: 10.1016/j.bbmt.2019.02.012.

24. Sivakumur P, Wraith JE. Bone marrow transplantation in mucopolysaccharidosis type IIIA: A comparison of an early treated patient with his untreated sibling. J Inherit Metab Dis. 1999 Oct;22(7):849-50. doi: 10.1023/a:1005526628598.

Neuromuscular diseases (NMDs) are a broad classification of heterogeneous groups of disorders characterized by progressive muscle weakness resulting from muscle or nerve dysfunction.¹ Diagnosis is based on symptoms and a full medical history, as well as on muscle and imaging tests (including electromyography, nerve-conduction studies, magnetic resonance imaging, muscle biopsy, and blood tests) to confirm or rule out specific NMDs.² Early diagnosis of NMDs can be difficult because symptoms overlap with those of many other diseases.

Although individually, NMDs are rare, collectively, they affect approximately 250,000 people in the United States. Disease types vary in regard to cause, symptoms, prevalence, age of onset, progression, and severity. Functional impairment from any NMD can lead to lifelong morbidities and shortened life expectancy.^1,3

Treatment options for NMDs are limited; most target symptoms, not disease progression. Although there is a need for safe and effective gene-based therapies for NMDs, there are challenges to developing and delivering such treatments that have impeded clinical success. These include a lack of understanding about disease pathology and drug targets, limited animal model systems, and few reliable biomarkers that are predictive of therapeutic success.^4,5

Amyotrophic lateral sclerosis

ALS is caused by progressive degeneration of upper- and lower-motor neurons, which eventually leads to respiratory failure and death 3 to 5 years after disease onset.^7-9 There are two subtypes: Familial ALS (10% of cases) and sporadic ALS (90% of cases). Commonly mutated ALS-associated genes^6,8 are:

• Superoxide dismutase type 1 (SOD1).
• Chromosome 9 open reading frame 72 (C9orf72).
• Transactive response DNA-binding protein 43 (TARDBP).
• Fused in sarcoma (FUS).

SOD1-targeted therapy is being studied, with early evidence of clinical success. Mutations in SOD1 account for 10% to 20% of familial ALS cases and 1% to 2% of sporadic ALS cases.^6,10 10 Mutations in C9orf72 account for 25 to 40% of familial ALS cases and 7% of sporadic ALS cases.^8,9,11 Mutations in TARDBP account for 3% of familial ALS cases and 2% of sporadic cases.¹² Mutations in FUS account for 4% of familial ALS cases and 1% of sporadic cases. Overall, these mutant proteins can trigger neurotoxicity, thus inducing motor-neuron death.^6,10
 

Treatment of ALS

Two treatments for ALS are Food and Drug Administration approved: riluzole (Rilutek), approved in 1995, and edaravone (Radicava), approved in 2017.

Riluzole is an oral anti-excitotoxic glutamate antagonist.¹¹ Approval of riluzole was based on the results of two studies that demonstrated a 2- to 3-month survival benefit.^10,14 For patients who have difficulty swallowing, an oral suspension (Tiglutik, approved in 2018) and an oral film (Exservan, approved in 2019) are available.

Edaravone is a free-radical scavenger that decreases oxidative stress and is administered intravenously (IV).^9,13,14 Findings from clinical trials suggest functional improvement or slower decline in function for some patients.

Although these two agents demonstrate modest therapeutic benefit, neither reverses progression of disease.^10,14
 

Gene-based therapy for ALS

Many non-viral strategies, including antisense oligonucleotide (ASO), monoclonal antibodies, reverse transcriptase inhibitors, and HGF gene replacement therapy are used as therapeutic approaches to SOD1, C9orf72, and FUS gene mutations in ALS patients, and are being evaluated in clinical studies^14,15 (Table 1^13-17).

• Change from baseline in CSF SOD1 protein concentration.¹⁷ Percent reduction in the total SOD1 protein level was much higher in the tofersen-treated group than in the control group (38% more than controls in the faster-progressing population; 26% more than controls in the slower-progressing population).¹⁸
• Change from baseline in neurofilament light-chain concentration in plasma.^17,18 Percent reduction in the level of neurofilament light chain was also observed to be higher in the tofersen-treated group than in the control group (67% more than controls in the faster-progressing population and 48% more than controls in the slower-progressing population).¹⁸

Because of these encouraging results, VALOR participants were moved to the ongoing open-label extension trial of tofersen (ClinicalTri-als.gov Identifier: NCT03070119), in which both groups were treated with the active agent.

These data suggest that early tofersen treatment might slow decline in faster-progressing patients and stabilize clinical function in slower-progressing patients.^18,19 Overall, most adverse events (AEs) in the trial among patients receiving active treatment were of mild or moderate severity, and were largely consistent with either disease progression or lumbar puncture–related complications.¹⁸

Because data from VALOR suggested potential benefit from tofersen, the ATLAS trial (ClinicalTrials.gov Identifier: NCT04856982) is investigating the clinical value of presymptomatic treatment and the optimal timing of initiation of therapy.^20,21 ATLAS is a phase 3, randomized, placebo-controlled trial that examines the clinical efficacy, safety, and tolerability of tofersen in presymptomatic adult carriers of SOD1 mutation who have an elevated neurofilament light-chain concentration.²¹ ATLAS will also evaluate the efficacy of tofersen when initiated before, rather than after, ALS manifests clinically. Enrollment is still open for this trial.^20,21

Latozinemab, also known as AL001, is a first-in-class monoclonal antibody, administered by IV infusion, that elevates levels of progranulin, a key regulator of the immune activity and lysosomal function in the brain.^22,23 Latozinemab limits progranulin endocytosis and degradation by sortilin inhibition.²² Progranulin gene mutations can reduce progranulin expression (by 50 to 70 percent reduction), which may cause neuro-degeneration due to abnormal accumulation of TAR-DNA-binding protein 43 (TDP-43) in the brain cells.^22,24 TDP-43 pathology has also been shown to be associated with C9orf72 mutations.²³ Although the mechanism is not fully understood, the role of progranulin deficiency in TDP-43 pathology is believed to be associated with neurodegenerative diseases like ALS.11,23,24,43 Previous animal models of chronic neurodegenera-tion have demonstrated how increased progranulin levels can be protective against TDP-43 pathology, increasing neuronal development and survival, thus potentially slowing disease progression.^23,24,43 Currently, latozinemab is being investigated in a randomized, double-blind, placebo-controlled, multicenter phase 2 trial (ClinicalTrials.gov Identifier: NCT05053035). Approximately, 45 C90rf72-associated ALS participants (≥ 18 years of age) will receive latozinemab or placebo infusions every 4 weeks (for 24 weeks). Study endpoints include safety, tolerability, PK, PD, as well as plasma, and CSF progranulin levels.²⁵ In previous studies, latozinemab demonstrated encouraging results in frontotemporal dementia (FTD) patients who carry a progranulin mutation. Because FTD was revealed to have significant genetic overlap with ALS, there is disease-modifying potential for latozinemab in ALS patients.^23,24

TPN-101 is a nucleoside analog reverse transcriptase inhibitor, administered orally, that was originally developed for human immunodeficiency virus (HIV) treatment. However, due to recent findings suggesting retrotransposon activity contributing to neurodegeneration in TDP-43 mediated diseases, including ALS and FTD, TNP-101 is being repurposed.²⁶ The safety and tolerability of TNP-101 are currently being evaluated in C9orf72-associated ALS and FTD patients (≥ 18 years of age). The study is a randomized, double-blind, placebo-controlled paral-lel-group phase 2a trial (ClinicalTrials.gov Identifier: NCT04993755) The study includes a screening period of 6 weeks, double-blind treatment period of 24 weeks, an open-label treatment period of 24 weeks, and 4 weeks of the post-treatment follow-up visit. Study endpoints include the incidence and severity of spontaneously reported treatment-emergent adverse events (TEAEs) associated with TNP-101 and placebo for a to-tal of 48 weeks.²⁷

ION363 is an investigational ASO, administered by IT injection, that selectively targets one of the FUS mutations (p.P525L), which is responsible for earlier disease onset and rapid ALS progression.^28,29 The clinical efficacy of ION363, specifically in clinical function and survival is being assessed in FUS-associated ALS patients (≥ 12 years of age). This randomized phase 3 study (ClinicalTrials.gov Identifier: NCT04768972) includes two parts; part 1 will consist of participants receiving a multi-dose regimen (1 dose every 4-12 weeks) of ION363 or placebo for 61 weeks followed by an open-label extension treatment period in part 2, which will consist of participants receiving ION363 (every 12 weeks) for 85 weeks. The primary endpoint of the study is the change from baseline to day 505 in functional impairment, using ALS Functional Rating Scale-Revised (ALSFRS-R). This measures functional disease severity, specifically in bulbar function, gross motor skills, fine motor skills, and respiratory. The score for all 12 questions can range from 0 (no function) to 4 (full function) with a total possible score of 48.³⁰

Engensis, also known as VM202, is a non-viral gene therapy, administered by intramuscular (IM) injection, that uses a plasmid to deliver the hepatocyte growth factor (HGF) gene to promote HGF protein production. The HGF protein plays a role in angiogenesis, the previous of muscle atrophy, and the promotion of neuronal survival and growth. Based on preclinical studies, increasing HGF protein production has been shown to reduce neurodegeneration, thus potentially halting or slowing ALS progression.³¹ Currently, the safety of engensis is being evaluated in ALS patients (18-80 years of age) in the REViVALS phase 2a (ClinicalTrials.gov Identifier: NCT04632225)/2b (ClinicalTrial.gov Identifier: NCT05176093).^32,33 The ReViVALS trial is a double-blind, randomized, placebo-controlled, multi-center study. The phase 2a study endpoints include the incidence of TEAEs, treatment-emergent serious adverse events (TESAEs), injection site reactions, and clinically significant labor-atory values post-treatment (engensis vs placebo group) for 180 days.³³ A phase 2b study will evaluate the long-term safety of engensis for an additional 6 months. Study endpoints include the incidence of AEs, changes from baseline in ALSFRS-R scores to evaluate improvement in muscle function, changes from baseline in quality of life using the ALS patient assessment questionnaire, time to all-cause mortality compared to placebo, etc.³²
 

Spinal muscular atrophy

SMA is a hereditary lower motor-neuron disease caused (in 95% of cases) by deletions or, less commonly, by mutations of the survival motor neuron 1 (SMN1) gene on chromosome 5q13 that encodes the SMN protein.⁶ Reduction in expression of the SMN protein causes motor neurons to degenerate.^36-38 Because of a large inverted duplication in chromosome 5q, two variants of SMN (SMN1 and SMN2) exist on each allele. The paralog gene, SMN2, also produces the SMN protein – although at a lower level (10% to 20% of total SMN protein production) than SMN1 does.

A single nucleotide substitution in SMN2 alters splicing and suppresses transcription of exon 7, resulting in a shortened mRNA strand that yields a truncated SMN protein product.^6,37,39 SMA is classified based on age of onset and maximum motor abilities achieved, ranging from the most severe (Type 0) to mildest (Type 4) disease.^36,40 Because SMA patients lack functional SMN1 (due to polymorphisms), disease severity is determined by copy numbers of SMN2.^6,39

 

Gene-based therapy for SMA

Three FDA-approved SMN treatments demonstrate clinically meaningful benefit in SMA: SMN2-targeting nusinersen [Spinraza] and risdiplam [Evrysdi], and SMN1-targeting onasemnogene abeparvovec-xioi [Zolgensma]³⁸ Additional approaches to SMA treatment are through SMN-independent therapies, which target muscle and nerve function. Research has strongly suggested that combined SMA therapies, specifically approved SMN-targeted and investigational SMN-independent treatments, such as GYM329 (also known as RO7204239) may be the best strategy to treat all ages, stages, and types of SMA.⁴¹ (Table 2^26-41).

• Percentage of motor milestones responders, as determined using Section 2 of the Hammersmith Infant Neurological Examination–Part 2.
• Event-free survival (that is, avoidance of combined endpoint of death or permanent ventilation).

ENDEAR met the first primary efficacy outcome, demonstrating statistically significant (P < .0001) improvement in motor milestones (head control, rolling, independent sitting, and standing). By 13 months of age, approximately 51% of nusinersen-treated participants showed improvement, compared with none in the control group.^46,47

The second primary endpoint was also met, with a statistically significant (P = .005) 47% decrease in mortality or permanent ventilation use.^46-48

The NURTURE (ClinicalTrial.gov Identifier: NCT02386553) study is also investigating the efficacy and safety of nusinersen. An ongoing, open-label, supportive phase 2 trial, NURTURE is evaluating the efficacy and safety of multiple doses of nusinersen in 25 presymptomatic SMA patients (≤ 6 weeks of age). The primary endpoint of this study is time to death or respiratory intervention.⁴⁹ Interim results demonstrate that 100% of presymptomatic infants are functioning without respiratory intervention after median follow-up of 2.9 years.^46-48

Although nusinersen has been shown to be generally safe in clinical studies, development of lumbar puncture–related complications, as well as the need for sedation during IT administration, might affect treatment tolerability in some patients.³⁹

Risdiplam was approved by the FDA in 2020 as the first orally administered small-molecule treatment of SMA (for patients ≤ 2 months of age).⁵² Risdiplam is a SMN2 splicing modifier, binding to the 5’ splice site of intron 7 and exonic splicing enhancer 2 in exon 7 of SMN2 pre-mRNA. This alternative splicing increases efficiency in SMN2 gene transcription, thus increasing SMN protein production in motor-neuron cells.³⁶ An important advantage of risdiplam is the convenience of oral administration: A large percentage of SMA patients (that is, those with Type 2 disease) have severe scoliosis, which can further complicate therapy or deter patients from using a treatment that is administered through the IT route.⁴⁰

FDA approval of risdiplam was based on clinical data from two pivotal studies, FIREFISH (ClinicalTrial.gov Identifier: NCT02913482) and SUNFISH (ClinicalTrial.gov Identifier: NCT02908685).^53-54

FIREFISH is an open-label, phase 2/3 ongoing trial in infants (1-7 months of age) with SMA Type 1. The study comprises two parts; Part 1 determined the dose of risdiplam used in Part 2, which assessed the efficacy and safety of risdiplam for 24 months. The primary endpoint was the percentage of infants sitting without support for 5 seconds after 12 months of treatment using the gross motor scale of the Bayley Scales of Infant and Toddler Development–Third Edition. A statistically significant (P < .0001) therapeutic benefit was observed in motor milestones. Approximately 29% of infants achieved the motor milestone of independent sitting for 5 seconds, which had not been observed in the natural history of SMA.^53-55

SUNFISH is an ongoing randomized, double-blind, placebo-controlled trial of risdiplam in adult and pediatric patients with SMA Types 2 and 3 (2-25 years old). This phase 2/3 study comprises two parts: Part 1 determined the dose (for 12 weeks) to be used for confirmatory Part 2 (for 12 to 24 months). The primary endpoint was the change from baseline on the 32-item Motor Function Measure at 12 months. The study met its primary endpoint, demonstrating statistically significant (P = .0156) improvement in motor function scores, with a 1.36-point increase in the risdiplam group, compared with a 0.19-point decrease in the control group.^54,55

Ongoing risdiplam clinical trials also include JEWELFISH (ClinicalTrial.gov Identifier: NCT03032172) and RAINBOW (ClinicalTrial.gov Identifier: NCT03779334).^56-57 JEWELFISH is an open-label, phase 2 trial assessing the safety of risdiplam in patients (6 months to 60 years old) who received prior treatment. The study has completed recruitment; results are pending.⁵⁶ RAINBOW is an ongoing, open-label, single-arm, phase 2 trial, evaluating the clinical efficacy and safety of risdiplam in SMA-presymptomatic newborns (≤ 6 weeks old). The study is open for enrollment.⁵⁷ Overall, interim results for JEWELFISH and RAINBOW appear promising.

In addition, combined SMA therapies, specifically risdiplam and GYM329 are currently being investigated to address the underlying cause and symptoms of SMA concurrently.⁵⁸ GYM329, is an investigational anti-myostatin antibody, selectively binding preforms of myostatin - pro-myostatin and latent myostatin, thus improving muscle mass and strength for SMA patients.⁵⁹ The safety and efficacy of GYM329 in combination with risdiplam is currently being investigated in 180 ambulant participants with SMA (2-10 years of age) in the MANATEE (ClinicalTrial.gov Identifier: NCT05115110) phase 2/3 trial. The MANATEE study is a two-part, seamless, randomized, placebo-controlled, double-blind trial. Part 1 will assess the safety of the combination treatment in approximately 36 participants; participants will receive both GYM329 (every 4 weeks) by subcutaneous (SC) injection into the abdomen and risdiplam (once per day) for 24 weeks followed by a 72-week open-label treatment period. ^54,58 The outcome measures include the incidence of AEs, percentage change from baseline in the contractile area of skeletal muscle (in dominant thigh and calf), change from baseline in RHS total score, and incidence of change from baseline in serum concentration (total myostatin, free latent myostatin, and mature myostatin) etc.⁵⁴ Part 2 will be conducted on 144 participants, specifically assessing the efficacy and safety of the optimal dose of GYM329 selected from Part 1 (combined with risdiplam) for 72 weeks. Once the treatment period is completed in either part, participants can partake in a 2-year open-label extension period.^54,58 Other outcome measures include change from baseline in lean muscle mass (assessed by full body dual-energy X- ray absorptiometry (DXA) scan), in time taken to walk/run 10 meters (measured by RHS), in time taken to rise from the floor (measured by RHS), etc.⁵⁴ Overall, this combination treatment has the potential to further improve SMA patient outcomes and will be further investigated in other patient populations (including non-ambulant patients and a broader age range) in the future.⁵⁸

An agent that alters SMN1 expression. Onasemnogene abeparvovec-xioi, FDA approved in 2019, was the first gene-replacement therapy indicated for treating SMA in children ≤ 2 years old.⁶⁰ Treatment utilizes an AAV vector type 9 (AAV9) to deliver a functional copy of SMN1 into target motor-neuron cells, thus increasing SMN protein production and improving motor function. This AAV serotype is ideal because it crosses the blood-brain barrier. Treatment is administered as a one-time IV fusion.^38,39,43

FDA approval was based on the STR1VE (ClinicalTrial.gov Identifier: NCT03306277) phase 3 study and START (ClinicalTrial.gov Identifier: NCT02122952) phase 1 study.^61,62 START was the first trial to investigate the safety and efficacy of onasemnogene abeparvovec-xioi in SMA Type 1 infants (< 6 months old). Results demonstrated remarkable clinical benefit, including 100% permanent ventilation-free survival and a 92% (11 of 12 patients) rate of improvement in motor function. Improvement in development milestones was also observed: 92% (11 of 12 patients) could sit without support for 5 seconds and 75% (9 of 12) could sit without support for 30 seconds.^14,61,63

The efficacy of onasemnogene abeparvovec-xioi seen in STR1VE was consistent with what was observed in START. STRIVE, a phase 3 open-label, single-dose trial, examined treatment efficacy and safety in 22 symptomatic infants (< 6 months old) with SMA Type 1 (one or two SMN2 copies). The primary endpoint was 30 seconds of independent sitting and event-free survival. Patients were followed for as long as 18 months. Treatment showed statistically significant (P < .0001) improvement in motor milestone development and event-free survival, which had not been observed in SMA Type 1 historically. Approximately 59% (13 of 22 patients) could sit independently for 30 seconds at 18 months of age. At 14 months of age, 91% (20 of 22 patients) were alive and achieved independence from ventilatory support.^34,35,53

Although many clinical studies suggest that onasemnogene abeparvovec-xioi can slow disease progression, the benefits and risks of long-term effects are still unknown. A 15-year observational study is investigating the long-term therapeutic effects and potential complications of onasemnogene abeparvovec-xioi. Participants in START were invited to enroll in this long-term follow-up study (ClinicalTrial.gov Identifier: NCT04042025).^66-67
 

Duchenne muscular dystrophy

DMD is the most common muscular dystrophy of childhood. With an X-linked pattern of inheritance, DMD is seen mostly in young males (1 in every 3,500 male births).^38,39,73 DMD is caused by mutation of the dystrophin encoding gene, or DMD, on the X chromosome. Deletion of one or more exons of DMD prevents production of the dystrophin protein, which leads to muscle degeneration.^38,39,43 Common DMD deletion hotspots are exon 51 (20% of cases), exon 53 (13% of cases), exon 44 (11% of cases), and exon 45 (12% of cases).⁷⁴ Nonsense mutations, which account for another 10% of DMD cases, occur when premature termination codons are found in the DMD gene. Those mutations yield truncated dystrophin protein products.^39,66

Therapy for DMD

There are many therapeutic options for DMD, including deflazacort (Emflaza), FDA approved in 2017, which has been shown to reduce inflammation and immune system activity in DMD patients (≥ 5 years old). Deflazacort is a corticosteroid prodrug; its active metabolite acts on the glucocorticoid receptor to exert anti-inflammatory and immunosuppressive effects. Studies have shown that muscle strength scores over 6-12 months and average time to loss of ambulation numerically favored deflazacort over placebo.^74,75

Gene-based therapy for DMD

Mutation-specific therapeutic approaches, such as exon skipping and nonsense suppression, have shown promise for the treatment of DMD (Table 3^58-79):

• ASO-mediated exon skipping allows one or more exons to be omitted from the mutated DMD mRNA.^74,75 Effective FDA-approved ASOs include golodirsen [Vyondys 53], viltolarsen [Viltepso], and casimersen [Amondys 45].⁷⁴
• An example of therapeutic suppression of nonsense mutations is ataluren [Translarna], an investigational agent that can promote premature termination codon read-through in DMD patients.⁶⁶

Another potential treatment approach is through the use of AAV gene transfer to treat DMD. However, because DMD is too large for the AAV vector (packaging size, 5.0 kb), microdystrophin genes (3.5-4 kb, are used as an alternative to fit into a single AAV vector.^39,76

Exon skipping targeting exon 51. Eteplirsen, approved in 2016, is indicated for the treatment of DMD patients with the confirmed DMD gene mutation that is amenable to exon 51 skipping. Eteplirsen binds to exon 51 of dystrophin pre-mRNA, causing it to be skipped, thus, restoring the reading frame in patients with DMD gene mutation amenable to exon 51 skipping. This exclusion promotes dystrophin production. Though the dystrophin protein is still functional, it is shortened.^38,77 Treatment is administered IV, once a week (over 35-60 minutes). Eteplirsen’s accelerated approval was based on 3 clinical studies (ClinicalTrial.gov Identifier: NCT01396239, NCT01540409, and NCT00844597.) ^78-81 The data demonstrated an increased expression of dystrophin in skeletal muscles in some DMD patients treated with eteplirsen. Though the clinical benefit of eteplirsen (including improved motor function) was not established, it was concluded by the FDA that the data were reasonably likely to predict clinical benefit. Continued approval for this indication may depend on the verification of a clinical benefit in confirmatory trials. Ongoing clinical trials include (ClinicalTrial.gov Identifier: NCT03992430 (MIS51ON), NCT03218995, and NCT03218995).^77,81,82

Vesleteplirsen, is an investigational agent that is designed for DMD patients who are amendable to exon 51 skip-ping. The mechanism of action of vesleteplirsen appears to be similar to that of eteplirsen.⁸³ The ongoing MOMENTUM (ClinicalTrial.gov Identifier: NCT04004065) phase 2 trial is assessing the safety and tolerability of vesleteplirsen at multiple-ascending dose levels (administered via IV infusion) in 60 participants (7-21 years of age). The study consists of two parts; participants receive escalating dose levels of vesleteplirsen (every 4 weeks) for 72 weeks during part A and participants receive the selected doses from part A (every 4 weeks) for 2 years during part B. Study endpoints include the number of AEs (up to 75 weeks) and the change from baseline to week 28 in dystrophin protein level. 84 Serious AEs of reversible hypomagnesemia were observed in part B, and as a result, the study protocol was amended to include magnesium supplementation and monitoring of magnesium levels.⁸³

Exon skipping targeting exon 53. Golodirsen, FDA approved in 2019, is indicated for the treatment of DMD in patients who have a confirmed DMD mutation that is amenable to exon 53 skipping. The mechanism of action is similar to eteplirsen, however, golodirsen is designed to bind to exon 53.^38,39 Treatment is administered by IV infusion over 35-60 minutes.

Approval of golodirsen was based primarily on a two-part, phase 1/2 clinical trial (ClinicalTrial.gov Identifier: NCT02310906). Part 1 was a randomized, placebo-controlled, dose-titration study that assessed multiple-dose efficacy in 12 DMD male patients, 6 to 15 years old, with deletions that were amenable to exon 53 skipping.

Part 2 was an open-label trial in 12 DMD patients from Part 1 of the trial plus 13 newly enrolled male DMD patients who were also amenable to exon 53 skipping and who had not already received treatment. Primary endpoints were change from baseline in total distance walked during the 6-minute walk test at Week 144 and dystrophin protein levels (measured by western blot testing) at Week 48. A statistically significant increase in the mean dystrophin level was observed, from a baseline 0.10% mean dystrophin level to a 1.02% mean dystrophin level after 48 weeks of treatment (P < .001). Common reported adverse events associated with golodirsen were headache, fever, abdominal pain, rash, and dermatitis. Renal toxicity was observed in preclinical studies of golodirsen but not in clinical studies.^80,85

Viltolarsen, approved in 2020, is also indicated for the treatment of DMD in patients with deletions amenable to exon 53 skipping. The mechanism of action and administration (IV infusion over 60 minutes) are similar to that of golodirsen.

Approval of viltolarsen was based on two phase 2 clinical trials (ClinicalTrial.gov Identifier: NCT02740972 and NCT03167255) in a total of 32 patients. NCT02740972 was a randomized, double-blind, placebo-controlled, dose-finding study that evaluated the clinical efficacy of viltolarsen in 16 male DMD patients (4-9 years old) for 24 weeks.

NCT03167255 was an open-label study that evaluated the safety and tolerability of viltolarsen in DMD male patients (5-18 years old) for 192 weeks. The efficacy endpoint was the change in dystrophin production from baseline after 24 weeks of treatment. A statistically significant increase in the mean dystrophin level was observed, from a 0.6% mean dystrophin level at baseline to a 5.9% mean dystrophin level at Week 25 (P = .01). The most common adverse events observed were upper respiratory tract infection, cough, fever, and injection-site reaction.^86-87

Exon skipping targeting exon 45. Casimersen was approved in 2021 for the treatment of DMD in patients with deletions amenable to exon 45 skipping.⁸⁸ Treatment is administered by IV infusion over 30-60 minutes. Approval was based on an increase in dystrophin production in skeletal muscle in treated patients. Clinical benefit was reported in interim results from the ESSENCE (ClinicalTrial.gov Identifier: NCT02500381) study, an ongoing double-blind, placebo-controlled phase 3 trial that is evaluating the efficacy of casimersen, compared with placebo, in male participants (6-13 years old) for 48 weeks. Efficacy is based on the change from baseline dystrophin intensity level, determined by immunohistochemistry, at Week 48.

Interim results from ESSENCE show a statistically significant increase in dystrophin production in the casimersen group, from a 0.9% mean dystrophin level at baseline to a 1.7% mean dystrophin level at Week 48 (P = .004); in the control group, a 0.54% mean dystrophin level at baseline increased to a 0.76% mean dystrophin level at Week 48 (P = .09). Common adverse events have included respiratory tract infection, headache, arthralgia, fever, and oropharyngeal pain. Renal toxicity was observed in preclinical data but not in clinical studies.^60,84

Targeting nonsense mutations. Ataluren is an investigational, orally administered nonsense mutation suppression therapy (through the read-through of stop codons).³⁷ Early clinical evidence supporting the use of ataluren in DMD was seen in an open-label, dose-ranging, phase 2a study (ClinicalTrial.gov Identifier: NCT00264888) in male DMD patients (≥ 5 years old) caused by nonsense mutation. The study demonstrated a modest (61% ) increase in dystrophin expression in 23 of 38 patients after 28 days of treatment.^37,91,92

However, a phase 2b randomized, double-blind, placebo-controlled trial (ClinicalTrial.gov Identifier: NCT00592553) and a subsequent confirmatory ACT DMD phase 3 study (ClinicalTrial.gov Identifier: NCT01826487) did not meet their primary endpoint of improvement in ambulation after 48 weeks as measured by the 6-minute walk test.^37,93,94 In ACT DMD, approximately 74% of the ataluren group did not experience disease progression, compared with 56% of the control group (P = 0386), measured by a change in the 6-minute walk test, which assessed ambulatory decline.^37,95

Based on limited data showing that ataluren is effective and well tolerated, the European Medicines Agency has given conditional approval for clinical use of the drug in Europe. However, ataluren was rejected by the FDA as a candidate therapy for DMD in the United States.²² Late-stage clinical studies of ataluren are ongoing in the United States.

AAV gene transfer with microdystrophin. Limitations on traditional gene-replacement therapy prompted exploration of gene-editing strategies for treating DMD, including using AAV-based vectors to transfer microdystrophin, an engineered version of DMD, into target muscles.⁴³ The microdystrophin gene is designed to produce a functional, truncated form of dystrophin, thus improving muscular function.

There are 3 ongoing investigational microdystrophin gene therapies that are in clinical development (ClinicalTrial.gov Identifier: NCT03368742 (IGNITE DMD), NCT04281485 (CIFFREO), and NCT05096221 (EMBARK)).^38,82

IGNITE DMD is a phase 1/2 randomized, controlled, single-ascending dose trial evaluating the safety and efficacy of a SGT-001, single IV infusion of AAV9 vector containing a microdystrophin construct in DMD patients (4-17 years old) for 12 months. At the conclusion of the trial, treatment and control groups will be followed for 5 years. The primary efficacy endpoint is the change from baseline in microdystrophin protein production in muscle-biopsy material, using western blot testing.⁹⁶ Long-term interim data on biopsy findings from three patients demonstrated clinical evidence of durable microdystrophin protein expression after 2 years of treatment.^96,97

The CIFFREO trial will assess the safety and efficacy of the PF-06939926 microdystrophin gene therapy, an investigational AAV9 containing microdystrophin, in approximately 99 ambulatory DMD patients (4-7 years of age). The study is a randomized, double-blind, placebo-controlled, multicenter phase 3 trial. The primary efficacy end-point is the change from baseline in the North Star Ambulatory Assessment (NSAA), which measures gross motor function. This will be assessed at 52 weeks; all study participants will be followed for a total of 5 years post-treatment.^98,99,100 Due to unexpected patient death (in a non-ambulatory cohort) in the phase 1b (in a non-ambulatory cohort) in the phase 1b (ClinicalTrial.gov Identifier: (NCT03362502) trial, microdystrophin gene therapy was immediately placed on clinical hold.^101,102 The amended study protocol required that all participants undergo one week of in-hospital observation after receiving treatment.¹⁰²

The EMBARK study is a global, randomized, double-blind, placebo-controlled, phase 3 trial that is evaluating the safety and efficacy of SRP-9001, which is a rAAVrh74.MHCK7.microdystrophin gene therapy. The AAV vector (rAAVrh74) contains the microdystrophin construct, driven by the skeletal and cardiac muscle–specific promoter, MHCK7.98,99 In the EMBARK study, approximately 120 participants with DMD (4-7 years of age) will be enrolled. The primary efficacy endpoint includes the change from baseline to week 52 in the NSAA total score.⁹⁹ Based on SRP-9001, data demonstrating consistent statistically significant functional improvements in NSAA total scores and timed function tests (after one-year post- treatment) in DMD patients from previous studies and an integrated analysis from multiple studies (ClinicalTrial.gov Identifier: NCT03375164, NCT03769116, and NCT04626674), the ongoing EMBARK has great promise.^103,104
 

Challenges ahead, but advancements realized

Novel gene-based therapies show significant potential for transforming the treatment of NMDs. The complex pathologies of NMDs have been a huge challenge to disease management in an area once considered unremediable by gene-based therapy. However, advancements in precision medicine – specifically, gene-delivery systems (for example, AAV9 and AAVrh74 vectors) combined with gene modification strategies (ASOs and AAV-mediated silencing) – have the potential to, first, revolutionize standards of care for sporadic and inherited NMDs and, second, significantly reduce disease burden.⁶

What will be determined to be the “best” therapeutic approach will, likely, vary from NMD to NMD; further investigation is required to determine which agents offer optimal clinical efficacy and safety profiles.⁴³ Furthermore, the key to therapeutic success will continue to be early detection and diagnosis – first, by better understanding disease pathology and drug targets and, second, by validation of reliable biomarkers that are predictive of therapeutic benefit.^4,5

To sum up, development challenges remain, but therapeutic approaches to ALS, SMA, and DMD that utilize novel gene-delivery and gene-manipulation tools show great promise.



Ms. Yewhalashet is a student in the masters of business and science program, with a concentration in healthcare economics, at Keck Graduate Institute Henry E. Riggs School of Applied Life Sciences, Claremont, Calif. Dr. Davis is professor of practice in clinical and regulatory affairs, Keck Graduate Institute Henry E. Riggs School of Applied Life Sciences.
 

References

1. Aitken M et al. Understanding neuromuscular disease care. IQVIA [Internet]. Oct 30, 2018. Accessed Mar 1, 2022. https://www.iqvia.com/insights/the-iqvia-institute/reports/understanding-neuromuscular-disease-care.

2. National Institute of Neurological Disorders and Stroke. Neurological diagnostic tests and procedures fact sheet. Updated Nov 15, 2021. Ac-cessed Mar 1, 2022. http://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Neurological-Diagnostic-Tests-and-Procedures-Fact.

3. Deenen JCW et al. The epidemiology of neuromuscular disorders: A comprehensive overview of the literature. J Neuromuscul Dis. 2015;2(1):73-85.

4. Cavazzoni P. The path forward: Advancing treatments and cures for neurodegenerative diseases. U.S. Food and Drug Administration. Jul 29, 2021. Accessed Mar 1, 2022. http://www.fda.gov/news-events/congressional-testimony/path-forward-advancing-treatments-and-cures-neurodegenerative-diseases-07292021.

5. Martier R, Konstantinova P. Gene therapy for neurodegenerative diseases: Slowing down the ticking clock. Front Neurosci. 2020 Sep 18;14:580179. doi: 10.3389/fnins.2020.580179.

6. Sun J, Roy S. Gene-based therapies for neurodegenerative diseases. Nat Neurosci. 2021 Mar;24(3):297-311. doi:10.1038/s41593-020-00778-1.

7. Amado DA, Davidson BL. Gene therapy for ALS: A review. Mol Ther. 2021 Dec 1;29(12):3345-58. doi:10.1016/j.ymthe.2021.04.008.

8. Yun Y, Ha Y. CRISPR/Cas9-mediated gene correction to understand ALS. Int J Mol Sci. 2020;21(11):3801. doi:10.3390/ijms21113801.

9. National Institute of Neurological Disorders and Stroke. Amyotrophic lateral sclerosis (ALS) fact sheet. Updated Nov 15, 2021. Accessed Mar 1, 2022. http://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Amyotrophic-Lateral-Sclerosis-ALS-Fact-Sheet.

10. Cappella M et al. Gene therapy for ALS – A perspective. Int J Mol Sci. 2019;20(18):4388. doi:10.3390/ijms20184388.

11. Abramzon YA, Fratta P, Traynor BJ, Chia R. The Overlapping Genetics of Amyotrophic Lateral Sclerosis and Frontotemporal Dementia. Front Neurosci. 2020;14. Accessed August 18, 2022. https://www.frontiersin.org/articles/10.3389/fnins.2020.00042

12. Giannini M, Bayona-Feliu A, Sproviero D, Barroso SI, Cereda C, Aguilera A. TDP-43 mutations link Amyotrophic Lateral Sclerosis with R-loop homeostasis and R loop-mediated DNA damage. PLOS Genet. 2020;16(12):e1009260. doi:10.1371/journal.pgen.1009260

13. FDA-approved drugs for treating ALS. The ALS Association [Internet]. Accessed Mar 1, 2022. http://www.als.org/navigating-als/living-with-als/fda-approved-drugs.

14. Jensen TL et al. Current and future prospects for gene therapy for rare genetic diseases affecting the brain and spinal cord. Front Mol Neurosci. 2021 Oct 6;14:695937. doi:10.3389/fnmol.2021.695937.

15. ALS Gene Targeted Therapies. The ALS Association. Accessed August 22, 2022. https://www.als.org/understanding-als/who-gets-als/genetic-testing/als-gene-targeted-therapies

16. Tofersen for ALS clears phase 1/2 trial, now in phase 3. Advances in Motion. Massachusetts General Hospital [Internet]. Sep 30, 2020. Accessed Mar 1, 2022. https://advances.massgeneral.org/neuro/journal.aspx?id=1699.17. Biogen. A study to evaluate the efficacy, safety, tol-erability, pharmacokinetics, and pharmacodynamics of BIIB067 administered to adult subjects with amyotrophic lateral sclerosis and confirmed superoxide dismutase 1 mutation. ClinicalTrials.gov Identifier: NCT02623699. Updated Jul 25, 2021. Accessed Feb 17, 2022. https://clinicaltrials.gov/ct2/show/NCT02623699.

18. Biogen. Biogen announces topline results from the tofersen phase 3 study and its open-label Extension in SOD1-ALS. Press release. Oct 17, 2021. Accessed Mar 1, 2022. https://investors.biogen.com/news-releases/news-release-details/biogen-announces-topline-results-tofersen-phase-3-study-and-its.

19. Biogen. An extension study to assess the long-term safety, tolerability, pharmacokinetics, and effect on disease progression of BIIB067 ad-ministered to previously treated adults with amyotrophic lateral sclerosis caused by superoxide dismutase 1 mutation. ClinicalTrials.gov Identi-fier: NCT03070119. Updated Sep 10, 2021. Accessed Feb 17, 2022. https://clinicaltrials.gov/ct2/show/NCT03070119.

20. MS MW. #AANAM – ATLAS Trial to Assess Tofersen in Presymptomatic SOD1 ALS. Accessed February 19, 2022. https://alsnewstoday.com/news-posts/2021/04/23/aanam-atlas-clinical-trial- tofersen-presymptomatic-sod1-als-patients/

21.Biogen. A phase 3 randomized, placebo-controlled trial with a longitudinal natural history run-in and open-label extension to evaluate BIIB067 initiated in clinically presymptomatic adults with a confirmed superoxide dismutase 1 mutation. ClinicalTrials.gov Identifier: NCT04856982. Updated Feb 18, 2022. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT04856982.

22. Latozinemab | ALZFORUM. Accessed August 19, 2022. https://www.alzforum.org/therapeutics/latozinemab

23. Alector Presents AL001 (latozinemab) Data from the FTD-C9orf72 Cohort of the INFRONT-2 Phase 2 Clinical Trial | Alector. Accessed August 18, 2022. https://investors.alector.com/news- releas-es/news-release-details/alector-presents-al001-latozinemab-data-ftd-c9orf72-cohort/

24. Alector Announces First Participant Dosed in Phase 2 Study Evaluating AL001 in Amyotrophic Lateral Sclerosis (ALS) | Alector. Accessed August 18, 2022. https://investors.alector.com/news- releases/news-release-details/lector-announces-first-participant-dosed-phase-2-study-0/ 25. A Phase 2 Study to Evaluate AL001 in C9orf72-Associated ALS - Full Text View - ClinicalTrials.gov. Accessed August 19, 2022. https://clinicaltrials.gov/ct2/show/NCT05053035

26.TPN-101 | ALZFORUM. Accessed August 19, 2022. https://www.alzforum.org/therapeutics/tpn- 101

27. Transposon Therapeutics, Inc. A Phase 2a Study of TPN-101 in Patients With Amyotrophic Lateral Sclerosis (ALS) and/or Frontotemporal Dementia (FTD) Associated With Hexanucleotide Repeat Expansion in the C9orf72 Gene (C9ORF72 ALS/FTD). clinicaltrials.gov; 2022. Ac-cessed August 17, 2022. https://clinicaltrials.gov/ct2/show/NCT04993755

28. Kerk SY, Bai Y, Smith J, et al. Homozygous ALS-linked FUS P525L mutations cell- autonomously perturb transcriptome profile and chem-oreceptor signaling in human iPSC microglia. Stem Cell Rep. 2022;17(3):678-692. doi:10.1016/j.stemcr.2022.01.004

29. ION363 | ALZFORUM. Accessed August 19, 2022. https://www.alzforum.org/therapeutics/ion363 30. Ionis Pharmaceuticals, Inc. A Phase 1-3 Study to Evaluate the Efficacy, Safety, Pharmacokinetics and Pharmacodynamics of Intrathecally Administered ION363 in Amyo-trophic Lateral Sclerosis Patients With Fused in Sarcoma Mutations (FUS-ALS). clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT04768972

31. PhD LF. Engensis (VM202) - ALS News Today. Accessed August 19, 2022. https://alsnewstoday.com/vm202/

32. Helixmith Co., Ltd. A 6-Month Extension Study Following Protocol VMALS-002-2 (A Phase 2a, Double-Blind, Randomized, Place-bo-Controlled, Multicenter Study to Assess the Safety of Engensis in Participants With Amyotrophic Lateral Sclerosis). clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT05176093 33. Safety of Engensis in Participants With Amyotrophic Lateral Sclerosis - Full Text View - ClinicalTrials.gov. Accessed August 19, 2022. https://clinicaltrials.gov/ct2/show/NCT04632225

34. Biogen. A phase 1, safety, tolerability, and distribution study of a microdose of radiolabeled BIIB067 co-administered with BIIB067 to healthy adults. ClinicalTrials.gov Identifier: NCT03764488. Updated Jul 19, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT03764488.

35. Ionis Pharmaceuticals Inc. A phase 1, double-blind, placebo-controlled, dose-escalation study of the safety, tolerability, and pharmacokinet-ics of ISIS 333611 administered intrathecally to patients with familial amyotrophic lateral sclerosis due to superoxide dismutase 1 gene muta-tions. ClinicalTrials.gov Identifier: NCT01041222. Updated Apr 13, 2012. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT01041222.

36. Messina S, Sframeli M. New treatments in spinal muscular atrophy: Positive results and new challenges. J Clin Med. 2020;9(7):2222. doi:10.3390/jcm9072222.

37. Scoto M et al. Genetic therapies for inherited neuromuscular disorders. Lancet Child Adolesc Health. 2018 Aug;2(8):600-9. doi:10.1016/S2352-4642(18)30140-8.

38. Abreu NJ, Waldrop MA. Overview of gene therapy in spinal muscular atrophy and Duchenne muscular dystrophy. Pediatr Pulmonol. 2021 Apr;56(4):710-20. doi:10.1002/ppul.25055.

39. Brandsema J, Cappa R. Genetically targeted therapies for inherited neuromuscular disorders. Practical Neurology [Internet]. Jul/Aug 2021:69-73. Accessed Mar 1, 2022. https://practicalneurology.com/articles/2021-july-aug/genetically-targeted-therapies-for-inherited-neuromuscular-disorders/pdf.

40. Ojala KS et al. In search of a cure: The development of therapeutics to alter the progression of spinal muscular atrophy. Brain Sci. 2021;11(2):194. doi:10.3390/brainsci11020194.

41. McCall S. Cure SMA Releases Updated Drug Pipeline. Cure SMA. Published December 13, 2021. Accessed August 21, 2022. https://www.curesma.org/cure-sma-releases-updated-drug-pipeline- 2021/ 42. FDA approves first drug for spinal muscular atrophy. U.S. Food and Drug Administration. News release. Dec 23, 2016. Accessed Mar 1, 2022. http://www.fda.gov/news-events/press-announcements/fda-approves-first-drug-spinal-muscular-atrophy.43. Kirschner J. Postnatal gene therapy for neuromuscular diseases – Opportunities and limitations. J Perinat Med. 2021 Sep;49(8):1011-5. doi:10.1515/jpm-2021-0435.

43. Terryn J, Verfaillie CM, Van Damme P. Tweaking Progranulin Expression: Therapeutic Avenues and Opportunities. Front Mol Neurosci. 2021;14. Accessed September 4, 2022. https://www.frontiersin.org/articles/10.3389/fnmol.2021.71303144.

44. Biogen. A phase 3, randomized, double-blind, sham-procedure controlled study to assess the clinical efficacy and safety of ISIS 396443 administered intrathecally in patients with later-onset spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT02292537. Updated Feb 17, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/study/NCT02292537.

45. Why Spinraza/later-onset studies. SPINRAZA® (nusinersen) [Internet]. Accessed Mar 1, 2022. www.spinraza.com/en_us/home/why-spinraza/later-onset-studies.html#scroll-tabs.

46. Biogen. A Phase 3, Randomized, Double-Blind, Sham-Procedure Controlled Study to Assess the Clinical Efficacy and Safety of ISIS 396443 Administered Intrathecally in Patients With Infantile- Onset Spinal Muscular Atrophy. clinicaltrials.gov; 2021. Accessed February 10, 2022. https://clinicaltrials.gov/ct2/show/results/NCT02193074

47. Early-onset SMA (Type 1) | SPINRAZA® (nusinersen). Accessed Mar 1, 2022. https://www.spinraza-hcp.com/en_us/home/why-spinraza/about-spinraza.html.

48. Finkel RS et al; ENDEAR Study Group. Nusinersen versus sham control in infantile-onset spinal muscular atrophy. N Engl J Med. 2017;377(18):1723-32. doi: 10.1056/NEJMoa1702752.

49. Biogen. An open-label study to assess the efficacy, safety, tolerability, and pharmacokinetics of multiple doses of ISIS 396443 delivered intrathecally to subjects with genetically diagnosed and presymptomatic spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT02386553. Updated Nov 18, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT02386553.

50. De Vivo DC et al; NURTURE Study Group. Nusinersen initiated in infants during the presymptomatic stage of spinal muscular atrophy: In-terim efficacy and safety results from the phase 2 NURTURE study. Neuromuscul Disord. 2019 Nov;29(11):842-56. doi:10.1016/j.nmd.2019.09.007.

51. Why Spinraza/presymptomatic study. SPINRAZA® (nusinersen) [Internet]. Accessed Feb 22, 2022. www.spinraza.com/en_us/home/why-spinraza/presymptomatic-study.html#scroll-tabs.

52. FDA approves oral treatment for spinal muscular atrophy. U.S. Food and Drug Administration. News release. Aug 7, 2020. Accessed Mar 1, 2022. http://www.fda.gov/news-events/press-announcements/fda-approves-oral-treatment-spinal-muscular-atrophy.

53. Hoffmann-La Roche. A two-part seamless, open-label, multicenter study to investigate the safety, tolerability, pharmacokinetics, pharmaco-dynamics and efficacy of risdiplam (RO7034067) in infants with type 1 spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT02913482. Updated Jan 21, 2022. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT02913482.

54. Hoffmann-La Roche. A two-part seamless, multi-center randomized, placebo-controlled, double-blind study to investigate the safety, tolera-bility, pharmacokinetics, pharmacodynamics and efficacy of risdiplam (RO7034067) in type 2 and 3 spinal muscular atrophy patients. Clinical-Trials.gov Identifier: NCT02908685. Updated Dec 28, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT02908685.

55. Genentech. Genentech’s risdiplam shows significant improvement in survival and motor milestones in infants with type 1 spinal muscular atrophy (SMA). Press release. Apr 27, 2020. Accessed Mar 1, 2022. http://www.gene.com/media/press-releases/14847/2020-04-27/genentechs-risdiplam-shows-significant-i

56. Hoffmann-La Roche. An open-label study to investigate the safety, tolerability, and pharmacokinetics/pharmacodynamics of risdiplam (RO7034067) in adult and pediatric patients with spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT03032172. Updated Jan 27, 2022. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT03032172.

57. Hoffmann-La Roche. An open-label study of risdiplam in infants with genetically diagnosed and presymptomatic spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT03779334. Updated Jan 27, 2022. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT03779334.

58. McCall S. Update on Genentech/Roche Initiation of MANATEE Clinical Study. Cure SMA. Published October 20, 2021. Accessed August 20, 2022. https://www.curesma.org/update-on- genentech-roche-initiation-of-manatee-clinical-study/

59. Abati E, Manini A, Comi GP, Corti S. Inhibition of myostatin and related signaling pathways for the treatment of muscle atrophy in motor neuron diseases. Cell Mol Life Sci. 2022;79(7):374. doi:10.1007/s00018-022-04408-w

60. FDA approves innovative gene therapy to treat pediatric patients with spinal muscular atrophy, a rare disease and leading genetic cause of infant mortality. U.S. Food and Drug Administration. News release. May 24, 2019. Accessed Mar 1, 2022. http://www.fda.gov/news-events/press-announcements/fda-approves-innovative-gene-therapy-treat-pediatric-patients-spinal-muscular-atrophy-rare-disease.

61. Novartis Gene Therapies. Phase I gene transfer clinical trial for spinal muscular atrophy type 1 delivering AVXS-101. ClinicalTrials.gov Identifier: NCT02122952. Updated Jun 14, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT02122952.

62. Novartis Gene Therapies. Phase 3, open-label, single-arm, single-dose gene replacement therapy clinical trial for patients with spinal mus-cular atrophy type 1 with one or two SMN2 copies delivering AVXS-101 by intravenous infusion. ClinicalTrials.gov Identifier: NCT03306277. Updated Jun 14, 2021. Accessed Feb 21, 2022. https://clinicaltrials.gov/ct2/show/NCT03306277.

63. Mendell JR et al. Single-dose gene-replacement therapy for spinal muscular atrophy. N Engl J Med. 2017;377(18):1713-22. doi:10.1056/NEJMoa1706198.

64. Symptomatic study results. ZOLGENSMA [Internet]. Updated Nov 2021. Accessed Mar 1, 2022. Error! Hyperlink reference not valid..

65. Novartis Gene Therapies. A global study of a single, one-time dose of AVXS-101 delivered to infants with genetically diagnosed and pre-symptomatic spinal muscular atrophy with multiple copies of SMN2. ClinicalTrials.gov Identifier: NCT03505099. Updated Jan 1, 2022. Ac-cessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT03505099.

66. Chiu W et al. Current genetics and potential gene-targeting therapeutics for neuromuscular diseases. Int J Mol Sci. 2020 Dec;21(24):9589. doi:10.3390/ijms21249589.

67. Novartis Gene Therapies. A long-term follow-up study of patients in the clinical trials for spinal muscular atrophy receiving AVXS-101. Clini-calTrials.gov Identifier: NCT04042025. Updated Jun 9, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT04042025.

68. Novartis Gene Therapies. Phase 3, open-label, single-arm, single-dose gene replacement therapy clinical trial for patients with spinal mus-cular atrophy type 1 with one or two SMN2 copies delivering AVXS-101 by intravenous infusion. ClinicalTrials.gov Identifier: NCT0383718. Up-dated Jan 11, 2022. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT03837184.

69. Biogen. An open-label, dose escalation study to assess the safety, tolerability and dose-range finding of multiple doses of ISIS 396443 de-livered intrathecally to patients with spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT01703988. Updated Apr 13, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT01703988.

70. Biogen. A study to assess the efficacy, safety, tolerability, and pharmacokinetics of multiple doses of ISIS 396443 delivered intrathecally to patients with infantile-onset spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT01839656. Updated Feb 17, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT01839656.

71. Biogen. An open-label extension study for patients with spinal muscular atrophy who previously participated in investigational studies of ISIS 396443. ClinicalTrials.gov Identifier: NCT02594124. Updated Nov 15, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT02594124.

72. Biogen. Escalating dose and randomized, controlled study of nusinersen (BIIB058) in participants with spinal muscular atrophy. ClinicalTri-als.gov Identifier: NCT04089566. Updated Feb 24, 2022. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT04089566.

73. National Center for Advancing Translational Sciences. Duchenne muscular dystrophy. Genetic and Rare Diseases Information Center. Up-dated Nov 2, 2020. Accessed Mar 1, 2022. https://rarediseases.info.nih.gov/diseases/6291/duchenne-muscular-dystrophy.

74. Matsuo M. Antisense oligonucleotide-mediated exon-skipping therapies: Precision medicine spreading from Duchenne muscular dystrophy. JMA J. 2021 Jul 15;4(3):232-40. doi:10.31662/jmaj.2021-0019.

75. FDA approves drug to treat Duchenne muscular dystrophy. U.S. Food and Drug Administration. News release. Feb 9, 2017. Accessed Mar 1, 2022. http://www.fda.gov/news-events/press-announcements/fda-approves-drug-treat-duchenne-muscular-dystrophy.74.

76. Duan D. Dystrophin gene replacement and gene repair therapy for Duchenne muscular dystrophy in 2016: An interview. Hum Gene Ther Clin Dev. 2016 Mar;27(1):9-18. doi:10.1089/humc.2016.001.

77. EXONDYS 51®. Parent Project Muscular Dystrophy. Accessed August 21, 2022. https://www.parentprojectmd.org/drug-development-pipeline/exondys-51/

78. Sarepta Therapeutics, Inc. A Randomized, Double-Blind, Placebo-Controlled, Multiple Dose Efficacy, Safety, Tolerability and Pharmacoki-netics Study of AVI-4658(Eteplirsen),in the Treatment of Ambulant Subjects With Duchenne Muscular Dystrophy. clinicaltrials.gov; 2020. Ac-cessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT01396239

79. Sarepta Therapeutics, Inc. Clinical Study to Assess the Safety Fo AVI-4658 in Subjects With Duchenne Muscular Dystrophy Due to a Frame-Shift Mutation Amenable to Correction by Skipping Exon 51. clinicaltrials.gov; 2015. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/study/NCT00844597

80. Sarepta Therapeutics, Inc. A 2-part, randomized, double-blind, placebo-controlled, dose-titration, safety, tolerability, and pharmacokinetics study (Part 1) followed by an open-label efficacy and safety evaluation (Part 2) of SRP-4053 in patients with Duchenne muscular dystrophy amenable to exon 53 skipping. ClinicalTrials.gov Identifier: NCT02310906. Updated Oct 19, 2020. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/results/NCT02310906.

81. Commissioner O of the. FDA grants accelerated approval to first drug for Duchenne muscular dystrophy. FDA. Published March 24, 2020. Accessed August 21, 2022. hDuchenne Muscular Dystrophy Amenable to Exon 51-Skipping Treatment. clinicaltrials.gov; 2022. Accessed Au-gust 18, 2022. https://clinicaltrials.gov/ct2/show/NCT04004065

109. National Center of Neurology and Psychiatry, Japan. Exploratory study of NS-065/NCNP-01 in Duchenne muscular dystrophy. ClinicalTri-als.gov Identifier: NCT02081625; Updated Feb 26, 2020. Accessed Mar 2, 2022. https://clinicaltrialsttps://www.fda.gov/news-events/press-announcements/fda-grants-accelerated-approval-first-drug-duchenne-muscular- dys-trophy

82. Duchenne Drug Development Pipeline. Parent Project Muscular Dystrophy. Accessed August 21, 2022. https://www.parentprojectmd.org/duchenne-drug-development-pipeline/

83. Sarepta Therapeutics Provides Update on SRP-5051 for the Treatment of Duchenne Muscular Dystrophy | Sarepta Therapeutics, Inc. Ac-cessed August 22, 2022. https://investorrelations.sarepta.com/news-releases/news-release-details/sarepta-therapeutics- pro-vides-update-srp-5051-treatment-duchenne

84. Sarepta Therapeutics, Inc. An Open-Label Extension Study for Patients With Duchenne Muscular Dystrophy Who Participated in Studies of SRP-5051. clinicaltrials.gov; 2021. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT03675126

85. VYONDYS 53. Prescribing information. Sarepta Therapeutics Inc.; 2019. Accessed Mar 2, 2022. http://www.accessdata.fda.gov/drugsatfda_docs/label/2019/211970s000lbl.pdf.

86. NS Pharma Inc. Long-term use of viltolarsen in boys with Duchenne muscular dystrophy in clinical practice (VILT-502). ClinicalTrials.gov Identifier: NCT04687020. Updated Nov 22, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT04687020.

87. VILTEPSO. Prescribing information. NS Pharma; 2020. Accessed Mar 2, 2022. http://www.accessdata.fda.gov/drugsatfda_docs/label/2020/212154s000lbl.pdf.

88. FDA approves targeted treatment for rare Duchenne muscular dystrophy mutation. U.S. Food and Drug Administration. News release. Feb 25, 2021. Accessed Mar 1, 2022. http://www.fda.gov/news-events/press-announcements/fda-approves-targeted-treatment-rare-duchenne-muscular-dystrophy-mutation-0.

89. Sarepta Therapeutics Inc. A double-blind, placebo-controlled, multi-center study with an open-label extension to evaluate the efficacy and safety of SRP-4045 and SRP-4053 in patients with Duchenne muscular dystrophy. Clinicaltrials.gov Identifier: NCT02500381. Updated Aug 19, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT02500381.

90. AMONDYS 45. Prescribing information. Sarepta Therapeutics Inc.; 2021. Accessed Feb 22, 2022. http://www.accessdata.fda.gov/drugsatfda_docs/label/2021/213026lbl.pdf.

91. Finkel RS et al. Phase 2a study of ataluren-mediated dystrophin production in patients with nonsense mutation Duchenne muscular dys-trophy. PLoS ONE. 2013;8(12):e81302. doi:10.1371/journal.pone.0081302.

92. PTC Therapeutics. A phase 2 study of PTC124 as an oral treatment for nonsense-mutation-mediated Duchenne muscular dystrophy. Clini-calTrials.gov Identifier: NCT00264888. Updated Jan 14, 2009. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT00264888.

93. PTC Therapeutics. A phase 2B efficacy and safety study of PTC124 in subjects with nonsense-mutation-mediated Duchenne and Becker muscular dystrophy. ClinicalTrials.gov Identifier: NCT00592553. Updated Apr 7, 2020. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT00592553.

94. PTC Therapeutics. A phase 3 efficacy and safety study of ataluren in patients with nonsense mutation dystrophinopathy. ClinicalTrials.gov Identifier: NCT01826487. Updated Aug 4, 2020. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT01826487.

95. Bushby K et al; PTC124-GD-007-DMD Study Group. Ataluren treatment of patients with nonsense mutation dystrophinopathy. Muscle Nerve. 2014 Oct;50(4):477-87. doi:10.1002/mus.24332.

96. Solid Biosciences LLC. A randomized, controlled, open-label, single-ascending dose, phase I/II study to investigate the safety and tolerabil-ity, and efficacy of intravenous SGT-001 in male adolescents and children with Duchenne muscular dystrophy. ClinicalTrials.gov Identifier: NCT03368742. Updated Aug 24, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT03368742.

97. Solid Biosciences reports 1.5-year data from patients in the ongoing IGNITE DMD phase I/II clinical trial of SGT-001. Press release. Solid Biosciences. Sep 27, 2021. Accessed Mar 2, 2022. http://www.solidbio.com/about/media/press-releases/solid-biosciences-reports-1-5-year-data-from-patients-in-the-ongoing-ignite-dmd-phase-i-ii-clinical-trial-of-sgt-001.

98. Potter RA et al. Dose-escalation study of systemically delivered rAAVrh74.MHCK7.microdystrophin in the mdx mouse model of Duchenne muscular dystrophy. Hum Gene Ther. 2021 Apr;32(7-8):375-89. doi:10.1089/hum.2019.255.

99. Sarepta Therapeutics, Inc. A Phase 3 Multinational, Randomized, Double-Blind, Placebo- Controlled Systemic Gene Delivery Study to Evaluate the Safety and Efficacy of SRP-9001 in Patients With Duchenne Muscular Dystrophy (EMBARK). clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT05096221

100. Pfizer. A PHASE 3, MULTICENTER, RANDOMIZED, DOUBLE-BLIND, PLACEBO CONTROLLED STUDY TO EVALUATE THE SAFETY AND EFFICACY OF PF 06939926 FOR THE TREATMENT OF DUCHENNE MUSCULAR DYSTROPHY. clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT04281485

101. Pfizer. A phase 1B multicenter open-label, single ascending dose study to evaluate the safety and tolerability of PF-06939926 in ambula-tory and non-ambulatory subjects with Duchenne muscular dystrophy. ClinicalTrials.gov Identifier: NCT03362502. Updated Mar 2, 2022. Ac-cessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT03362502.

102. MS MW. Phase 3 CIFFREO DMD Gene Therapy Trial Slated to Begin in June in US. Accessed August 21, 2022. https://musculardystrophynews.com/news/phase-3-trial-of-pfizers-gene-therapy- expected-to-open-in-us-in-june/

103. SRP-9001. Parent Project Muscular Dystrophy. Accessed August 22, 2022. https://www.parentprojectmd.org/drug-development-pipeline/srp-9001-micro-dystrophin-gene- transfer/

104. Sarepta Therapeutics’ Investigational Gene Therapy SRP-9001 for Duchenne Muscular Dystrophy Demonstrates Significant Functional Improvements Across Multiple Studies | Sarepta Therapeutics, Inc. Accessed August 22, 2022. https://investorrelations.sarepta.com/news-releases/news-release- details/sarepta-therapeutics-investigational-gene-therapy-srp-9001

105. Sarepta Therapeutics, Inc. An Open-Label Safety, Tolerability, and Efficacy Study of Eteplirsen in Patients With Duchenne Muscular Dys-trophy Who Have Completed Study 4658-102.clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT03985878

106. Sarepta Therapeutics, Inc. An Open-Label Safety, Tolerability, and Pharmacokinetics Study of Eteplirsen in Young Patients With Duchenne Mus-cular Dystrophy Amenable to Exon 51 Skipping. clinicaltrials.gov; 2021. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT03218995

107.Sarepta Therapeutics, Inc. A Randomized, Double-Blind, Dose Finding and Comparison Study of the Safety and Efficacy of a High Dose of Eteplirsen, Preceded by an Open-Label Dose Escalation, in Patients With Duchenne Muscular Dystrophy With Deletion Mutations Amenable to Exon 51 Skipping. clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT03992430

108. Sarepta Therapeutics, Inc. A Phase 2, Two-Part, Multiple-Ascending-Dose Study of SRP-5051 for Dose Determination, Then Dose Ex-pansion, in Patients With .gov/ct2/show/NCT02081625.

110. NS Pharma Inc. A phase II, dose finding study to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics of NS-065/NCNP-01 in boys with Duchenne muscular dystrophy (DMD). ClinicalTrials.gov Identifier: NCT02740972. Updated Dec 7, 2021. Ac-cessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT02740972.

111. NS Pharma Inc. A phase II, open-label, extension study to assess the safety and efficacy of NS-065/NCNP-01 in boys with Duchenne muscular dystrophy (DMD). ClinicalTrials.gov Identifier: NCT03167255. Updated Nov 24, 2021. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT03167255.

112. NS Pharma Inc. A phase 2 open label study to assess the safety, tolerability, and efficacy of viltolarsen in ambulant and non-ambulant boys with Duchenne muscular dystrophy (DMD) compared with natural history controls. ClinicalTrials.gov Identifier: NCT04956289. Updated Feb 1, 2022. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT04956289.

113. NS Pharma Inc. A phase 3 randomized, double-blind, placebo-controlled, multi-center study to assess the efficacy and safety of viltolarsen in ambulant boys with Duchenne muscular dystrophy (DMD). ClinicalTrials.gov Identifier: NCT04060199. Updated Nov 16, 2021. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT04060199.

114. NS Pharma Inc. A phase 3, multi-center, open-label extension study to assess the safety and efficacy of viltolarsen in ambulant boys with Duchenne muscular dystrophy (DMD). ClinicalTrials.gov Identifier: NCT04768062. Updated Nov 16, 2021. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT04768062.

115. Sarepta Therapeutics Inc. A randomized, double-blind, placebo-controlled, dose-titration, safety, tolerability, and pharmacokinetics study followed by an open-label safety and efficacy evaluation of SRP-4045 in advanced-stage patients with Duchenne muscular dystrophy amena-ble to exon 45 skipping. ClinicalTrials.gov Identifier: NCT02530905. Updated May 17, 2021. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT02530905.

116. Sarepta Therapeutics Inc. Long-term, open-label extension study for patients with Duchenne muscular dystrophy enrolled in clinical trials evaluating casimersen or golodirsen. ClinicalTrials.gov Identifier: NCT03532542. Updated Dec 20, 2021. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT03532542.

117. PTC Therapeutics. A phase 2 study of the safety, pharmacokinetics, and pharmacodynamics of ataluren (PTC124®) in patients aged ≥2 to <5 years old with nonsense mutation dystrophinopathy. ClinicalTrials.gov Identifier: NCT02819557. Updated Aug 28, 2020. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT02819557.

118. PTC Therapeutics. Phase 2, non-interventional, clinical study to assess dystrophin levels in subjects with nonsense mutation Duchenne muscular dystrophy who have been treated with ataluren for ≥ 9 months. ClinicalTrials.gov Identifier: NCT03796637. Updated Apr 10, 2020. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT03796637.

119. PTC Therapeutics. An Open-Label Study Evaluating the Safety and Pharmacokinetics of Ataluren in Children From ≥6 Months to <2 Years of Age With Nonsense Mutation Duchenne Muscular Dystrophy. clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT04336826 120. PTC Therapeutics. An open-label study for previously treated ataluren (PTC124®) pa-tients with nonsense mutation dystrophinopathy. ClinicalTrials.gov Identifier: NCT01557400. Updated Nov 25, 2020. Accessed Feb 21, 2022. https://clinicaltrials.gov/ct2/show/NCT01557400.

121. PTC Therapeutics. An open-label, safety study for ataluren (PTC124) patients with nonsense mutation dystrophinopathy. ClinicalTrials.gov Identifier: NCT01247207. Updated Feb 16, 2022. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT01247207.

122. PTC Therapeutics. A phase 3, randomized, double-blind, placebo-controlled efficacy and safety study of ataluren in patients with non-sense mutation Duchenne muscular dystrophy and open-label extension. ClinicalTrials.gov Identifier: NCT03179631. Updated Feb 8, 2022. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT03179631.

123. Sarepta Therapeutics, Inc. An Open-Label, Systemic Gene Delivery Study Using Commercial Process Material to Evaluate the Safety of and Expression From SRP-9001 in Subjects With Duchenne Muscular Dystrophy (ENDEAVOR). clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT04626674

124. Sarepta Therapeutics, Inc. Systemic Gene Delivery Phase I/IIa Clinical Trial for Duchenne Muscular Dystrophy Using RAA-Vrh74.MHCK7.Micro-Dystrophin (MicroDys-IV-001). clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT03375164

125. Sarepta Therapeutics Inc. A multicenter, randomized, double-blind, placebo-controlled trial for Duchenne muscular dystrophy using SRP-9001. ClinicalTrials.gov Identifier: NCT03769116. Updated Dec 2021. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT03769116.

126. Hoffmann-La Roche. A Two-Part, Seamless, Multi-Center, Randomized, Placebo-Controlled, Double-Blind Study to Investigate the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics and Efficacy of RO7204239 in Combination With Risdiplam (RO7034067) in Ambulant Pa-tients With Spinal Muscular Atrophy. clinicaltrials.gov; 2022. Accessed September 1, 2022. https://clinicaltrials.gov/ct2/show/NCT05115110

Neuromuscular diseases (NMDs) are a broad classification of heterogeneous groups of disorders characterized by progressive muscle weakness resulting from muscle or nerve dysfunction.¹ Diagnosis is based on symptoms and a full medical history, as well as on muscle and imaging tests (including electromyography, nerve-conduction studies, magnetic resonance imaging, muscle biopsy, and blood tests) to confirm or rule out specific NMDs.² Early diagnosis of NMDs can be difficult because symptoms overlap with those of many other diseases.

Although individually, NMDs are rare, collectively, they affect approximately 250,000 people in the United States. Disease types vary in regard to cause, symptoms, prevalence, age of onset, progression, and severity. Functional impairment from any NMD can lead to lifelong morbidities and shortened life expectancy.^1,3

Treatment options for NMDs are limited; most target symptoms, not disease progression. Although there is a need for safe and effective gene-based therapies for NMDs, there are challenges to developing and delivering such treatments that have impeded clinical success. These include a lack of understanding about disease pathology and drug targets, limited animal model systems, and few reliable biomarkers that are predictive of therapeutic success.^4,5

Amyotrophic lateral sclerosis

ALS is caused by progressive degeneration of upper- and lower-motor neurons, which eventually leads to respiratory failure and death 3 to 5 years after disease onset.^7-9 There are two subtypes: Familial ALS (10% of cases) and sporadic ALS (90% of cases). Commonly mutated ALS-associated genes^6,8 are:

• Superoxide dismutase type 1 (SOD1).
• Chromosome 9 open reading frame 72 (C9orf72).
• Transactive response DNA-binding protein 43 (TARDBP).
• Fused in sarcoma (FUS).

SOD1-targeted therapy is being studied, with early evidence of clinical success. Mutations in SOD1 account for 10% to 20% of familial ALS cases and 1% to 2% of sporadic ALS cases.^6,10 10 Mutations in C9orf72 account for 25 to 40% of familial ALS cases and 7% of sporadic ALS cases.^8,9,11 Mutations in TARDBP account for 3% of familial ALS cases and 2% of sporadic cases.¹² Mutations in FUS account for 4% of familial ALS cases and 1% of sporadic cases. Overall, these mutant proteins can trigger neurotoxicity, thus inducing motor-neuron death.^6,10
 

Treatment of ALS

Two treatments for ALS are Food and Drug Administration approved: riluzole (Rilutek), approved in 1995, and edaravone (Radicava), approved in 2017.

Riluzole is an oral anti-excitotoxic glutamate antagonist.¹¹ Approval of riluzole was based on the results of two studies that demonstrated a 2- to 3-month survival benefit.^10,14 For patients who have difficulty swallowing, an oral suspension (Tiglutik, approved in 2018) and an oral film (Exservan, approved in 2019) are available.

Edaravone is a free-radical scavenger that decreases oxidative stress and is administered intravenously (IV).^9,13,14 Findings from clinical trials suggest functional improvement or slower decline in function for some patients.

Although these two agents demonstrate modest therapeutic benefit, neither reverses progression of disease.^10,14
 

Gene-based therapy for ALS

Many non-viral strategies, including antisense oligonucleotide (ASO), monoclonal antibodies, reverse transcriptase inhibitors, and HGF gene replacement therapy are used as therapeutic approaches to SOD1, C9orf72, and FUS gene mutations in ALS patients, and are being evaluated in clinical studies^14,15 (Table 1^13-17).

• Change from baseline in CSF SOD1 protein concentration.¹⁷ Percent reduction in the total SOD1 protein level was much higher in the tofersen-treated group than in the control group (38% more than controls in the faster-progressing population; 26% more than controls in the slower-progressing population).¹⁸
• Change from baseline in neurofilament light-chain concentration in plasma.^17,18 Percent reduction in the level of neurofilament light chain was also observed to be higher in the tofersen-treated group than in the control group (67% more than controls in the faster-progressing population and 48% more than controls in the slower-progressing population).¹⁸

Because of these encouraging results, VALOR participants were moved to the ongoing open-label extension trial of tofersen (ClinicalTri-als.gov Identifier: NCT03070119), in which both groups were treated with the active agent.

These data suggest that early tofersen treatment might slow decline in faster-progressing patients and stabilize clinical function in slower-progressing patients.^18,19 Overall, most adverse events (AEs) in the trial among patients receiving active treatment were of mild or moderate severity, and were largely consistent with either disease progression or lumbar puncture–related complications.¹⁸

Because data from VALOR suggested potential benefit from tofersen, the ATLAS trial (ClinicalTrials.gov Identifier: NCT04856982) is investigating the clinical value of presymptomatic treatment and the optimal timing of initiation of therapy.^20,21 ATLAS is a phase 3, randomized, placebo-controlled trial that examines the clinical efficacy, safety, and tolerability of tofersen in presymptomatic adult carriers of SOD1 mutation who have an elevated neurofilament light-chain concentration.²¹ ATLAS will also evaluate the efficacy of tofersen when initiated before, rather than after, ALS manifests clinically. Enrollment is still open for this trial.^20,21

Latozinemab, also known as AL001, is a first-in-class monoclonal antibody, administered by IV infusion, that elevates levels of progranulin, a key regulator of the immune activity and lysosomal function in the brain.^22,23 Latozinemab limits progranulin endocytosis and degradation by sortilin inhibition.²² Progranulin gene mutations can reduce progranulin expression (by 50 to 70 percent reduction), which may cause neuro-degeneration due to abnormal accumulation of TAR-DNA-binding protein 43 (TDP-43) in the brain cells.^22,24 TDP-43 pathology has also been shown to be associated with C9orf72 mutations.²³ Although the mechanism is not fully understood, the role of progranulin deficiency in TDP-43 pathology is believed to be associated with neurodegenerative diseases like ALS.11,23,24,43 Previous animal models of chronic neurodegenera-tion have demonstrated how increased progranulin levels can be protective against TDP-43 pathology, increasing neuronal development and survival, thus potentially slowing disease progression.^23,24,43 Currently, latozinemab is being investigated in a randomized, double-blind, placebo-controlled, multicenter phase 2 trial (ClinicalTrials.gov Identifier: NCT05053035). Approximately, 45 C90rf72-associated ALS participants (≥ 18 years of age) will receive latozinemab or placebo infusions every 4 weeks (for 24 weeks). Study endpoints include safety, tolerability, PK, PD, as well as plasma, and CSF progranulin levels.²⁵ In previous studies, latozinemab demonstrated encouraging results in frontotemporal dementia (FTD) patients who carry a progranulin mutation. Because FTD was revealed to have significant genetic overlap with ALS, there is disease-modifying potential for latozinemab in ALS patients.^23,24

TPN-101 is a nucleoside analog reverse transcriptase inhibitor, administered orally, that was originally developed for human immunodeficiency virus (HIV) treatment. However, due to recent findings suggesting retrotransposon activity contributing to neurodegeneration in TDP-43 mediated diseases, including ALS and FTD, TNP-101 is being repurposed.²⁶ The safety and tolerability of TNP-101 are currently being evaluated in C9orf72-associated ALS and FTD patients (≥ 18 years of age). The study is a randomized, double-blind, placebo-controlled paral-lel-group phase 2a trial (ClinicalTrials.gov Identifier: NCT04993755) The study includes a screening period of 6 weeks, double-blind treatment period of 24 weeks, an open-label treatment period of 24 weeks, and 4 weeks of the post-treatment follow-up visit. Study endpoints include the incidence and severity of spontaneously reported treatment-emergent adverse events (TEAEs) associated with TNP-101 and placebo for a to-tal of 48 weeks.²⁷

ION363 is an investigational ASO, administered by IT injection, that selectively targets one of the FUS mutations (p.P525L), which is responsible for earlier disease onset and rapid ALS progression.^28,29 The clinical efficacy of ION363, specifically in clinical function and survival is being assessed in FUS-associated ALS patients (≥ 12 years of age). This randomized phase 3 study (ClinicalTrials.gov Identifier: NCT04768972) includes two parts; part 1 will consist of participants receiving a multi-dose regimen (1 dose every 4-12 weeks) of ION363 or placebo for 61 weeks followed by an open-label extension treatment period in part 2, which will consist of participants receiving ION363 (every 12 weeks) for 85 weeks. The primary endpoint of the study is the change from baseline to day 505 in functional impairment, using ALS Functional Rating Scale-Revised (ALSFRS-R). This measures functional disease severity, specifically in bulbar function, gross motor skills, fine motor skills, and respiratory. The score for all 12 questions can range from 0 (no function) to 4 (full function) with a total possible score of 48.³⁰

Engensis, also known as VM202, is a non-viral gene therapy, administered by intramuscular (IM) injection, that uses a plasmid to deliver the hepatocyte growth factor (HGF) gene to promote HGF protein production. The HGF protein plays a role in angiogenesis, the previous of muscle atrophy, and the promotion of neuronal survival and growth. Based on preclinical studies, increasing HGF protein production has been shown to reduce neurodegeneration, thus potentially halting or slowing ALS progression.³¹ Currently, the safety of engensis is being evaluated in ALS patients (18-80 years of age) in the REViVALS phase 2a (ClinicalTrials.gov Identifier: NCT04632225)/2b (ClinicalTrial.gov Identifier: NCT05176093).^32,33 The ReViVALS trial is a double-blind, randomized, placebo-controlled, multi-center study. The phase 2a study endpoints include the incidence of TEAEs, treatment-emergent serious adverse events (TESAEs), injection site reactions, and clinically significant labor-atory values post-treatment (engensis vs placebo group) for 180 days.³³ A phase 2b study will evaluate the long-term safety of engensis for an additional 6 months. Study endpoints include the incidence of AEs, changes from baseline in ALSFRS-R scores to evaluate improvement in muscle function, changes from baseline in quality of life using the ALS patient assessment questionnaire, time to all-cause mortality compared to placebo, etc.³²
 

Spinal muscular atrophy

SMA is a hereditary lower motor-neuron disease caused (in 95% of cases) by deletions or, less commonly, by mutations of the survival motor neuron 1 (SMN1) gene on chromosome 5q13 that encodes the SMN protein.⁶ Reduction in expression of the SMN protein causes motor neurons to degenerate.^36-38 Because of a large inverted duplication in chromosome 5q, two variants of SMN (SMN1 and SMN2) exist on each allele. The paralog gene, SMN2, also produces the SMN protein – although at a lower level (10% to 20% of total SMN protein production) than SMN1 does.

A single nucleotide substitution in SMN2 alters splicing and suppresses transcription of exon 7, resulting in a shortened mRNA strand that yields a truncated SMN protein product.^6,37,39 SMA is classified based on age of onset and maximum motor abilities achieved, ranging from the most severe (Type 0) to mildest (Type 4) disease.^36,40 Because SMA patients lack functional SMN1 (due to polymorphisms), disease severity is determined by copy numbers of SMN2.^6,39

 

Gene-based therapy for SMA

Three FDA-approved SMN treatments demonstrate clinically meaningful benefit in SMA: SMN2-targeting nusinersen [Spinraza] and risdiplam [Evrysdi], and SMN1-targeting onasemnogene abeparvovec-xioi [Zolgensma]³⁸ Additional approaches to SMA treatment are through SMN-independent therapies, which target muscle and nerve function. Research has strongly suggested that combined SMA therapies, specifically approved SMN-targeted and investigational SMN-independent treatments, such as GYM329 (also known as RO7204239) may be the best strategy to treat all ages, stages, and types of SMA.⁴¹ (Table 2^26-41).

• Percentage of motor milestones responders, as determined using Section 2 of the Hammersmith Infant Neurological Examination–Part 2.
• Event-free survival (that is, avoidance of combined endpoint of death or permanent ventilation).

ENDEAR met the first primary efficacy outcome, demonstrating statistically significant (P < .0001) improvement in motor milestones (head control, rolling, independent sitting, and standing). By 13 months of age, approximately 51% of nusinersen-treated participants showed improvement, compared with none in the control group.^46,47

The second primary endpoint was also met, with a statistically significant (P = .005) 47% decrease in mortality or permanent ventilation use.^46-48

The NURTURE (ClinicalTrial.gov Identifier: NCT02386553) study is also investigating the efficacy and safety of nusinersen. An ongoing, open-label, supportive phase 2 trial, NURTURE is evaluating the efficacy and safety of multiple doses of nusinersen in 25 presymptomatic SMA patients (≤ 6 weeks of age). The primary endpoint of this study is time to death or respiratory intervention.⁴⁹ Interim results demonstrate that 100% of presymptomatic infants are functioning without respiratory intervention after median follow-up of 2.9 years.^46-48

Although nusinersen has been shown to be generally safe in clinical studies, development of lumbar puncture–related complications, as well as the need for sedation during IT administration, might affect treatment tolerability in some patients.³⁹

Risdiplam was approved by the FDA in 2020 as the first orally administered small-molecule treatment of SMA (for patients ≤ 2 months of age).⁵² Risdiplam is a SMN2 splicing modifier, binding to the 5’ splice site of intron 7 and exonic splicing enhancer 2 in exon 7 of SMN2 pre-mRNA. This alternative splicing increases efficiency in SMN2 gene transcription, thus increasing SMN protein production in motor-neuron cells.³⁶ An important advantage of risdiplam is the convenience of oral administration: A large percentage of SMA patients (that is, those with Type 2 disease) have severe scoliosis, which can further complicate therapy or deter patients from using a treatment that is administered through the IT route.⁴⁰

FDA approval of risdiplam was based on clinical data from two pivotal studies, FIREFISH (ClinicalTrial.gov Identifier: NCT02913482) and SUNFISH (ClinicalTrial.gov Identifier: NCT02908685).^53-54

FIREFISH is an open-label, phase 2/3 ongoing trial in infants (1-7 months of age) with SMA Type 1. The study comprises two parts; Part 1 determined the dose of risdiplam used in Part 2, which assessed the efficacy and safety of risdiplam for 24 months. The primary endpoint was the percentage of infants sitting without support for 5 seconds after 12 months of treatment using the gross motor scale of the Bayley Scales of Infant and Toddler Development–Third Edition. A statistically significant (P < .0001) therapeutic benefit was observed in motor milestones. Approximately 29% of infants achieved the motor milestone of independent sitting for 5 seconds, which had not been observed in the natural history of SMA.^53-55

SUNFISH is an ongoing randomized, double-blind, placebo-controlled trial of risdiplam in adult and pediatric patients with SMA Types 2 and 3 (2-25 years old). This phase 2/3 study comprises two parts: Part 1 determined the dose (for 12 weeks) to be used for confirmatory Part 2 (for 12 to 24 months). The primary endpoint was the change from baseline on the 32-item Motor Function Measure at 12 months. The study met its primary endpoint, demonstrating statistically significant (P = .0156) improvement in motor function scores, with a 1.36-point increase in the risdiplam group, compared with a 0.19-point decrease in the control group.^54,55

Ongoing risdiplam clinical trials also include JEWELFISH (ClinicalTrial.gov Identifier: NCT03032172) and RAINBOW (ClinicalTrial.gov Identifier: NCT03779334).^56-57 JEWELFISH is an open-label, phase 2 trial assessing the safety of risdiplam in patients (6 months to 60 years old) who received prior treatment. The study has completed recruitment; results are pending.⁵⁶ RAINBOW is an ongoing, open-label, single-arm, phase 2 trial, evaluating the clinical efficacy and safety of risdiplam in SMA-presymptomatic newborns (≤ 6 weeks old). The study is open for enrollment.⁵⁷ Overall, interim results for JEWELFISH and RAINBOW appear promising.

In addition, combined SMA therapies, specifically risdiplam and GYM329 are currently being investigated to address the underlying cause and symptoms of SMA concurrently.⁵⁸ GYM329, is an investigational anti-myostatin antibody, selectively binding preforms of myostatin - pro-myostatin and latent myostatin, thus improving muscle mass and strength for SMA patients.⁵⁹ The safety and efficacy of GYM329 in combination with risdiplam is currently being investigated in 180 ambulant participants with SMA (2-10 years of age) in the MANATEE (ClinicalTrial.gov Identifier: NCT05115110) phase 2/3 trial. The MANATEE study is a two-part, seamless, randomized, placebo-controlled, double-blind trial. Part 1 will assess the safety of the combination treatment in approximately 36 participants; participants will receive both GYM329 (every 4 weeks) by subcutaneous (SC) injection into the abdomen and risdiplam (once per day) for 24 weeks followed by a 72-week open-label treatment period. ^54,58 The outcome measures include the incidence of AEs, percentage change from baseline in the contractile area of skeletal muscle (in dominant thigh and calf), change from baseline in RHS total score, and incidence of change from baseline in serum concentration (total myostatin, free latent myostatin, and mature myostatin) etc.⁵⁴ Part 2 will be conducted on 144 participants, specifically assessing the efficacy and safety of the optimal dose of GYM329 selected from Part 1 (combined with risdiplam) for 72 weeks. Once the treatment period is completed in either part, participants can partake in a 2-year open-label extension period.^54,58 Other outcome measures include change from baseline in lean muscle mass (assessed by full body dual-energy X- ray absorptiometry (DXA) scan), in time taken to walk/run 10 meters (measured by RHS), in time taken to rise from the floor (measured by RHS), etc.⁵⁴ Overall, this combination treatment has the potential to further improve SMA patient outcomes and will be further investigated in other patient populations (including non-ambulant patients and a broader age range) in the future.⁵⁸

An agent that alters SMN1 expression. Onasemnogene abeparvovec-xioi, FDA approved in 2019, was the first gene-replacement therapy indicated for treating SMA in children ≤ 2 years old.⁶⁰ Treatment utilizes an AAV vector type 9 (AAV9) to deliver a functional copy of SMN1 into target motor-neuron cells, thus increasing SMN protein production and improving motor function. This AAV serotype is ideal because it crosses the blood-brain barrier. Treatment is administered as a one-time IV fusion.^38,39,43

FDA approval was based on the STR1VE (ClinicalTrial.gov Identifier: NCT03306277) phase 3 study and START (ClinicalTrial.gov Identifier: NCT02122952) phase 1 study.^61,62 START was the first trial to investigate the safety and efficacy of onasemnogene abeparvovec-xioi in SMA Type 1 infants (< 6 months old). Results demonstrated remarkable clinical benefit, including 100% permanent ventilation-free survival and a 92% (11 of 12 patients) rate of improvement in motor function. Improvement in development milestones was also observed: 92% (11 of 12 patients) could sit without support for 5 seconds and 75% (9 of 12) could sit without support for 30 seconds.^14,61,63

The efficacy of onasemnogene abeparvovec-xioi seen in STR1VE was consistent with what was observed in START. STRIVE, a phase 3 open-label, single-dose trial, examined treatment efficacy and safety in 22 symptomatic infants (< 6 months old) with SMA Type 1 (one or two SMN2 copies). The primary endpoint was 30 seconds of independent sitting and event-free survival. Patients were followed for as long as 18 months. Treatment showed statistically significant (P < .0001) improvement in motor milestone development and event-free survival, which had not been observed in SMA Type 1 historically. Approximately 59% (13 of 22 patients) could sit independently for 30 seconds at 18 months of age. At 14 months of age, 91% (20 of 22 patients) were alive and achieved independence from ventilatory support.^34,35,53

Although many clinical studies suggest that onasemnogene abeparvovec-xioi can slow disease progression, the benefits and risks of long-term effects are still unknown. A 15-year observational study is investigating the long-term therapeutic effects and potential complications of onasemnogene abeparvovec-xioi. Participants in START were invited to enroll in this long-term follow-up study (ClinicalTrial.gov Identifier: NCT04042025).^66-67
 

Duchenne muscular dystrophy

DMD is the most common muscular dystrophy of childhood. With an X-linked pattern of inheritance, DMD is seen mostly in young males (1 in every 3,500 male births).^38,39,73 DMD is caused by mutation of the dystrophin encoding gene, or DMD, on the X chromosome. Deletion of one or more exons of DMD prevents production of the dystrophin protein, which leads to muscle degeneration.^38,39,43 Common DMD deletion hotspots are exon 51 (20% of cases), exon 53 (13% of cases), exon 44 (11% of cases), and exon 45 (12% of cases).⁷⁴ Nonsense mutations, which account for another 10% of DMD cases, occur when premature termination codons are found in the DMD gene. Those mutations yield truncated dystrophin protein products.^39,66

Therapy for DMD

There are many therapeutic options for DMD, including deflazacort (Emflaza), FDA approved in 2017, which has been shown to reduce inflammation and immune system activity in DMD patients (≥ 5 years old). Deflazacort is a corticosteroid prodrug; its active metabolite acts on the glucocorticoid receptor to exert anti-inflammatory and immunosuppressive effects. Studies have shown that muscle strength scores over 6-12 months and average time to loss of ambulation numerically favored deflazacort over placebo.^74,75

Gene-based therapy for DMD

Mutation-specific therapeutic approaches, such as exon skipping and nonsense suppression, have shown promise for the treatment of DMD (Table 3^58-79):

• ASO-mediated exon skipping allows one or more exons to be omitted from the mutated DMD mRNA.^74,75 Effective FDA-approved ASOs include golodirsen [Vyondys 53], viltolarsen [Viltepso], and casimersen [Amondys 45].⁷⁴
• An example of therapeutic suppression of nonsense mutations is ataluren [Translarna], an investigational agent that can promote premature termination codon read-through in DMD patients.⁶⁶

Another potential treatment approach is through the use of AAV gene transfer to treat DMD. However, because DMD is too large for the AAV vector (packaging size, 5.0 kb), microdystrophin genes (3.5-4 kb, are used as an alternative to fit into a single AAV vector.^39,76

Exon skipping targeting exon 51. Eteplirsen, approved in 2016, is indicated for the treatment of DMD patients with the confirmed DMD gene mutation that is amenable to exon 51 skipping. Eteplirsen binds to exon 51 of dystrophin pre-mRNA, causing it to be skipped, thus, restoring the reading frame in patients with DMD gene mutation amenable to exon 51 skipping. This exclusion promotes dystrophin production. Though the dystrophin protein is still functional, it is shortened.^38,77 Treatment is administered IV, once a week (over 35-60 minutes). Eteplirsen’s accelerated approval was based on 3 clinical studies (ClinicalTrial.gov Identifier: NCT01396239, NCT01540409, and NCT00844597.) ^78-81 The data demonstrated an increased expression of dystrophin in skeletal muscles in some DMD patients treated with eteplirsen. Though the clinical benefit of eteplirsen (including improved motor function) was not established, it was concluded by the FDA that the data were reasonably likely to predict clinical benefit. Continued approval for this indication may depend on the verification of a clinical benefit in confirmatory trials. Ongoing clinical trials include (ClinicalTrial.gov Identifier: NCT03992430 (MIS51ON), NCT03218995, and NCT03218995).^77,81,82

Vesleteplirsen, is an investigational agent that is designed for DMD patients who are amendable to exon 51 skip-ping. The mechanism of action of vesleteplirsen appears to be similar to that of eteplirsen.⁸³ The ongoing MOMENTUM (ClinicalTrial.gov Identifier: NCT04004065) phase 2 trial is assessing the safety and tolerability of vesleteplirsen at multiple-ascending dose levels (administered via IV infusion) in 60 participants (7-21 years of age). The study consists of two parts; participants receive escalating dose levels of vesleteplirsen (every 4 weeks) for 72 weeks during part A and participants receive the selected doses from part A (every 4 weeks) for 2 years during part B. Study endpoints include the number of AEs (up to 75 weeks) and the change from baseline to week 28 in dystrophin protein level. 84 Serious AEs of reversible hypomagnesemia were observed in part B, and as a result, the study protocol was amended to include magnesium supplementation and monitoring of magnesium levels.⁸³

Exon skipping targeting exon 53. Golodirsen, FDA approved in 2019, is indicated for the treatment of DMD in patients who have a confirmed DMD mutation that is amenable to exon 53 skipping. The mechanism of action is similar to eteplirsen, however, golodirsen is designed to bind to exon 53.^38,39 Treatment is administered by IV infusion over 35-60 minutes.

Approval of golodirsen was based primarily on a two-part, phase 1/2 clinical trial (ClinicalTrial.gov Identifier: NCT02310906). Part 1 was a randomized, placebo-controlled, dose-titration study that assessed multiple-dose efficacy in 12 DMD male patients, 6 to 15 years old, with deletions that were amenable to exon 53 skipping.

Part 2 was an open-label trial in 12 DMD patients from Part 1 of the trial plus 13 newly enrolled male DMD patients who were also amenable to exon 53 skipping and who had not already received treatment. Primary endpoints were change from baseline in total distance walked during the 6-minute walk test at Week 144 and dystrophin protein levels (measured by western blot testing) at Week 48. A statistically significant increase in the mean dystrophin level was observed, from a baseline 0.10% mean dystrophin level to a 1.02% mean dystrophin level after 48 weeks of treatment (P < .001). Common reported adverse events associated with golodirsen were headache, fever, abdominal pain, rash, and dermatitis. Renal toxicity was observed in preclinical studies of golodirsen but not in clinical studies.^80,85

Viltolarsen, approved in 2020, is also indicated for the treatment of DMD in patients with deletions amenable to exon 53 skipping. The mechanism of action and administration (IV infusion over 60 minutes) are similar to that of golodirsen.

Approval of viltolarsen was based on two phase 2 clinical trials (ClinicalTrial.gov Identifier: NCT02740972 and NCT03167255) in a total of 32 patients. NCT02740972 was a randomized, double-blind, placebo-controlled, dose-finding study that evaluated the clinical efficacy of viltolarsen in 16 male DMD patients (4-9 years old) for 24 weeks.

NCT03167255 was an open-label study that evaluated the safety and tolerability of viltolarsen in DMD male patients (5-18 years old) for 192 weeks. The efficacy endpoint was the change in dystrophin production from baseline after 24 weeks of treatment. A statistically significant increase in the mean dystrophin level was observed, from a 0.6% mean dystrophin level at baseline to a 5.9% mean dystrophin level at Week 25 (P = .01). The most common adverse events observed were upper respiratory tract infection, cough, fever, and injection-site reaction.^86-87

Exon skipping targeting exon 45. Casimersen was approved in 2021 for the treatment of DMD in patients with deletions amenable to exon 45 skipping.⁸⁸ Treatment is administered by IV infusion over 30-60 minutes. Approval was based on an increase in dystrophin production in skeletal muscle in treated patients. Clinical benefit was reported in interim results from the ESSENCE (ClinicalTrial.gov Identifier: NCT02500381) study, an ongoing double-blind, placebo-controlled phase 3 trial that is evaluating the efficacy of casimersen, compared with placebo, in male participants (6-13 years old) for 48 weeks. Efficacy is based on the change from baseline dystrophin intensity level, determined by immunohistochemistry, at Week 48.

Interim results from ESSENCE show a statistically significant increase in dystrophin production in the casimersen group, from a 0.9% mean dystrophin level at baseline to a 1.7% mean dystrophin level at Week 48 (P = .004); in the control group, a 0.54% mean dystrophin level at baseline increased to a 0.76% mean dystrophin level at Week 48 (P = .09). Common adverse events have included respiratory tract infection, headache, arthralgia, fever, and oropharyngeal pain. Renal toxicity was observed in preclinical data but not in clinical studies.^60,84

Targeting nonsense mutations. Ataluren is an investigational, orally administered nonsense mutation suppression therapy (through the read-through of stop codons).³⁷ Early clinical evidence supporting the use of ataluren in DMD was seen in an open-label, dose-ranging, phase 2a study (ClinicalTrial.gov Identifier: NCT00264888) in male DMD patients (≥ 5 years old) caused by nonsense mutation. The study demonstrated a modest (61% ) increase in dystrophin expression in 23 of 38 patients after 28 days of treatment.^37,91,92

However, a phase 2b randomized, double-blind, placebo-controlled trial (ClinicalTrial.gov Identifier: NCT00592553) and a subsequent confirmatory ACT DMD phase 3 study (ClinicalTrial.gov Identifier: NCT01826487) did not meet their primary endpoint of improvement in ambulation after 48 weeks as measured by the 6-minute walk test.^37,93,94 In ACT DMD, approximately 74% of the ataluren group did not experience disease progression, compared with 56% of the control group (P = 0386), measured by a change in the 6-minute walk test, which assessed ambulatory decline.^37,95

Based on limited data showing that ataluren is effective and well tolerated, the European Medicines Agency has given conditional approval for clinical use of the drug in Europe. However, ataluren was rejected by the FDA as a candidate therapy for DMD in the United States.²² Late-stage clinical studies of ataluren are ongoing in the United States.

AAV gene transfer with microdystrophin. Limitations on traditional gene-replacement therapy prompted exploration of gene-editing strategies for treating DMD, including using AAV-based vectors to transfer microdystrophin, an engineered version of DMD, into target muscles.⁴³ The microdystrophin gene is designed to produce a functional, truncated form of dystrophin, thus improving muscular function.

There are 3 ongoing investigational microdystrophin gene therapies that are in clinical development (ClinicalTrial.gov Identifier: NCT03368742 (IGNITE DMD), NCT04281485 (CIFFREO), and NCT05096221 (EMBARK)).^38,82

IGNITE DMD is a phase 1/2 randomized, controlled, single-ascending dose trial evaluating the safety and efficacy of a SGT-001, single IV infusion of AAV9 vector containing a microdystrophin construct in DMD patients (4-17 years old) for 12 months. At the conclusion of the trial, treatment and control groups will be followed for 5 years. The primary efficacy endpoint is the change from baseline in microdystrophin protein production in muscle-biopsy material, using western blot testing.⁹⁶ Long-term interim data on biopsy findings from three patients demonstrated clinical evidence of durable microdystrophin protein expression after 2 years of treatment.^96,97

The CIFFREO trial will assess the safety and efficacy of the PF-06939926 microdystrophin gene therapy, an investigational AAV9 containing microdystrophin, in approximately 99 ambulatory DMD patients (4-7 years of age). The study is a randomized, double-blind, placebo-controlled, multicenter phase 3 trial. The primary efficacy end-point is the change from baseline in the North Star Ambulatory Assessment (NSAA), which measures gross motor function. This will be assessed at 52 weeks; all study participants will be followed for a total of 5 years post-treatment.^98,99,100 Due to unexpected patient death (in a non-ambulatory cohort) in the phase 1b (in a non-ambulatory cohort) in the phase 1b (ClinicalTrial.gov Identifier: (NCT03362502) trial, microdystrophin gene therapy was immediately placed on clinical hold.^101,102 The amended study protocol required that all participants undergo one week of in-hospital observation after receiving treatment.¹⁰²

The EMBARK study is a global, randomized, double-blind, placebo-controlled, phase 3 trial that is evaluating the safety and efficacy of SRP-9001, which is a rAAVrh74.MHCK7.microdystrophin gene therapy. The AAV vector (rAAVrh74) contains the microdystrophin construct, driven by the skeletal and cardiac muscle–specific promoter, MHCK7.98,99 In the EMBARK study, approximately 120 participants with DMD (4-7 years of age) will be enrolled. The primary efficacy endpoint includes the change from baseline to week 52 in the NSAA total score.⁹⁹ Based on SRP-9001, data demonstrating consistent statistically significant functional improvements in NSAA total scores and timed function tests (after one-year post- treatment) in DMD patients from previous studies and an integrated analysis from multiple studies (ClinicalTrial.gov Identifier: NCT03375164, NCT03769116, and NCT04626674), the ongoing EMBARK has great promise.^103,104
 

Challenges ahead, but advancements realized

Novel gene-based therapies show significant potential for transforming the treatment of NMDs. The complex pathologies of NMDs have been a huge challenge to disease management in an area once considered unremediable by gene-based therapy. However, advancements in precision medicine – specifically, gene-delivery systems (for example, AAV9 and AAVrh74 vectors) combined with gene modification strategies (ASOs and AAV-mediated silencing) – have the potential to, first, revolutionize standards of care for sporadic and inherited NMDs and, second, significantly reduce disease burden.⁶

What will be determined to be the “best” therapeutic approach will, likely, vary from NMD to NMD; further investigation is required to determine which agents offer optimal clinical efficacy and safety profiles.⁴³ Furthermore, the key to therapeutic success will continue to be early detection and diagnosis – first, by better understanding disease pathology and drug targets and, second, by validation of reliable biomarkers that are predictive of therapeutic benefit.^4,5

To sum up, development challenges remain, but therapeutic approaches to ALS, SMA, and DMD that utilize novel gene-delivery and gene-manipulation tools show great promise.



Ms. Yewhalashet is a student in the masters of business and science program, with a concentration in healthcare economics, at Keck Graduate Institute Henry E. Riggs School of Applied Life Sciences, Claremont, Calif. Dr. Davis is professor of practice in clinical and regulatory affairs, Keck Graduate Institute Henry E. Riggs School of Applied Life Sciences.
 

References

1. Aitken M et al. Understanding neuromuscular disease care. IQVIA [Internet]. Oct 30, 2018. Accessed Mar 1, 2022. https://www.iqvia.com/insights/the-iqvia-institute/reports/understanding-neuromuscular-disease-care.

2. National Institute of Neurological Disorders and Stroke. Neurological diagnostic tests and procedures fact sheet. Updated Nov 15, 2021. Ac-cessed Mar 1, 2022. http://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Neurological-Diagnostic-Tests-and-Procedures-Fact.

3. Deenen JCW et al. The epidemiology of neuromuscular disorders: A comprehensive overview of the literature. J Neuromuscul Dis. 2015;2(1):73-85.

4. Cavazzoni P. The path forward: Advancing treatments and cures for neurodegenerative diseases. U.S. Food and Drug Administration. Jul 29, 2021. Accessed Mar 1, 2022. http://www.fda.gov/news-events/congressional-testimony/path-forward-advancing-treatments-and-cures-neurodegenerative-diseases-07292021.

5. Martier R, Konstantinova P. Gene therapy for neurodegenerative diseases: Slowing down the ticking clock. Front Neurosci. 2020 Sep 18;14:580179. doi: 10.3389/fnins.2020.580179.

6. Sun J, Roy S. Gene-based therapies for neurodegenerative diseases. Nat Neurosci. 2021 Mar;24(3):297-311. doi:10.1038/s41593-020-00778-1.

7. Amado DA, Davidson BL. Gene therapy for ALS: A review. Mol Ther. 2021 Dec 1;29(12):3345-58. doi:10.1016/j.ymthe.2021.04.008.

8. Yun Y, Ha Y. CRISPR/Cas9-mediated gene correction to understand ALS. Int J Mol Sci. 2020;21(11):3801. doi:10.3390/ijms21113801.

9. National Institute of Neurological Disorders and Stroke. Amyotrophic lateral sclerosis (ALS) fact sheet. Updated Nov 15, 2021. Accessed Mar 1, 2022. http://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Amyotrophic-Lateral-Sclerosis-ALS-Fact-Sheet.

10. Cappella M et al. Gene therapy for ALS – A perspective. Int J Mol Sci. 2019;20(18):4388. doi:10.3390/ijms20184388.

11. Abramzon YA, Fratta P, Traynor BJ, Chia R. The Overlapping Genetics of Amyotrophic Lateral Sclerosis and Frontotemporal Dementia. Front Neurosci. 2020;14. Accessed August 18, 2022. https://www.frontiersin.org/articles/10.3389/fnins.2020.00042

12. Giannini M, Bayona-Feliu A, Sproviero D, Barroso SI, Cereda C, Aguilera A. TDP-43 mutations link Amyotrophic Lateral Sclerosis with R-loop homeostasis and R loop-mediated DNA damage. PLOS Genet. 2020;16(12):e1009260. doi:10.1371/journal.pgen.1009260

13. FDA-approved drugs for treating ALS. The ALS Association [Internet]. Accessed Mar 1, 2022. http://www.als.org/navigating-als/living-with-als/fda-approved-drugs.

14. Jensen TL et al. Current and future prospects for gene therapy for rare genetic diseases affecting the brain and spinal cord. Front Mol Neurosci. 2021 Oct 6;14:695937. doi:10.3389/fnmol.2021.695937.

15. ALS Gene Targeted Therapies. The ALS Association. Accessed August 22, 2022. https://www.als.org/understanding-als/who-gets-als/genetic-testing/als-gene-targeted-therapies

16. Tofersen for ALS clears phase 1/2 trial, now in phase 3. Advances in Motion. Massachusetts General Hospital [Internet]. Sep 30, 2020. Accessed Mar 1, 2022. https://advances.massgeneral.org/neuro/journal.aspx?id=1699.17. Biogen. A study to evaluate the efficacy, safety, tol-erability, pharmacokinetics, and pharmacodynamics of BIIB067 administered to adult subjects with amyotrophic lateral sclerosis and confirmed superoxide dismutase 1 mutation. ClinicalTrials.gov Identifier: NCT02623699. Updated Jul 25, 2021. Accessed Feb 17, 2022. https://clinicaltrials.gov/ct2/show/NCT02623699.

18. Biogen. Biogen announces topline results from the tofersen phase 3 study and its open-label Extension in SOD1-ALS. Press release. Oct 17, 2021. Accessed Mar 1, 2022. https://investors.biogen.com/news-releases/news-release-details/biogen-announces-topline-results-tofersen-phase-3-study-and-its.

19. Biogen. An extension study to assess the long-term safety, tolerability, pharmacokinetics, and effect on disease progression of BIIB067 ad-ministered to previously treated adults with amyotrophic lateral sclerosis caused by superoxide dismutase 1 mutation. ClinicalTrials.gov Identi-fier: NCT03070119. Updated Sep 10, 2021. Accessed Feb 17, 2022. https://clinicaltrials.gov/ct2/show/NCT03070119.

20. MS MW. #AANAM – ATLAS Trial to Assess Tofersen in Presymptomatic SOD1 ALS. Accessed February 19, 2022. https://alsnewstoday.com/news-posts/2021/04/23/aanam-atlas-clinical-trial- tofersen-presymptomatic-sod1-als-patients/

21.Biogen. A phase 3 randomized, placebo-controlled trial with a longitudinal natural history run-in and open-label extension to evaluate BIIB067 initiated in clinically presymptomatic adults with a confirmed superoxide dismutase 1 mutation. ClinicalTrials.gov Identifier: NCT04856982. Updated Feb 18, 2022. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT04856982.

22. Latozinemab | ALZFORUM. Accessed August 19, 2022. https://www.alzforum.org/therapeutics/latozinemab

23. Alector Presents AL001 (latozinemab) Data from the FTD-C9orf72 Cohort of the INFRONT-2 Phase 2 Clinical Trial | Alector. Accessed August 18, 2022. https://investors.alector.com/news- releas-es/news-release-details/alector-presents-al001-latozinemab-data-ftd-c9orf72-cohort/

24. Alector Announces First Participant Dosed in Phase 2 Study Evaluating AL001 in Amyotrophic Lateral Sclerosis (ALS) | Alector. Accessed August 18, 2022. https://investors.alector.com/news- releases/news-release-details/lector-announces-first-participant-dosed-phase-2-study-0/ 25. A Phase 2 Study to Evaluate AL001 in C9orf72-Associated ALS - Full Text View - ClinicalTrials.gov. Accessed August 19, 2022. https://clinicaltrials.gov/ct2/show/NCT05053035

26.TPN-101 | ALZFORUM. Accessed August 19, 2022. https://www.alzforum.org/therapeutics/tpn- 101

27. Transposon Therapeutics, Inc. A Phase 2a Study of TPN-101 in Patients With Amyotrophic Lateral Sclerosis (ALS) and/or Frontotemporal Dementia (FTD) Associated With Hexanucleotide Repeat Expansion in the C9orf72 Gene (C9ORF72 ALS/FTD). clinicaltrials.gov; 2022. Ac-cessed August 17, 2022. https://clinicaltrials.gov/ct2/show/NCT04993755

28. Kerk SY, Bai Y, Smith J, et al. Homozygous ALS-linked FUS P525L mutations cell- autonomously perturb transcriptome profile and chem-oreceptor signaling in human iPSC microglia. Stem Cell Rep. 2022;17(3):678-692. doi:10.1016/j.stemcr.2022.01.004

29. ION363 | ALZFORUM. Accessed August 19, 2022. https://www.alzforum.org/therapeutics/ion363 30. Ionis Pharmaceuticals, Inc. A Phase 1-3 Study to Evaluate the Efficacy, Safety, Pharmacokinetics and Pharmacodynamics of Intrathecally Administered ION363 in Amyo-trophic Lateral Sclerosis Patients With Fused in Sarcoma Mutations (FUS-ALS). clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT04768972

31. PhD LF. Engensis (VM202) - ALS News Today. Accessed August 19, 2022. https://alsnewstoday.com/vm202/

32. Helixmith Co., Ltd. A 6-Month Extension Study Following Protocol VMALS-002-2 (A Phase 2a, Double-Blind, Randomized, Place-bo-Controlled, Multicenter Study to Assess the Safety of Engensis in Participants With Amyotrophic Lateral Sclerosis). clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT05176093 33. Safety of Engensis in Participants With Amyotrophic Lateral Sclerosis - Full Text View - ClinicalTrials.gov. Accessed August 19, 2022. https://clinicaltrials.gov/ct2/show/NCT04632225

34. Biogen. A phase 1, safety, tolerability, and distribution study of a microdose of radiolabeled BIIB067 co-administered with BIIB067 to healthy adults. ClinicalTrials.gov Identifier: NCT03764488. Updated Jul 19, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT03764488.

35. Ionis Pharmaceuticals Inc. A phase 1, double-blind, placebo-controlled, dose-escalation study of the safety, tolerability, and pharmacokinet-ics of ISIS 333611 administered intrathecally to patients with familial amyotrophic lateral sclerosis due to superoxide dismutase 1 gene muta-tions. ClinicalTrials.gov Identifier: NCT01041222. Updated Apr 13, 2012. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT01041222.

36. Messina S, Sframeli M. New treatments in spinal muscular atrophy: Positive results and new challenges. J Clin Med. 2020;9(7):2222. doi:10.3390/jcm9072222.

37. Scoto M et al. Genetic therapies for inherited neuromuscular disorders. Lancet Child Adolesc Health. 2018 Aug;2(8):600-9. doi:10.1016/S2352-4642(18)30140-8.

38. Abreu NJ, Waldrop MA. Overview of gene therapy in spinal muscular atrophy and Duchenne muscular dystrophy. Pediatr Pulmonol. 2021 Apr;56(4):710-20. doi:10.1002/ppul.25055.

39. Brandsema J, Cappa R. Genetically targeted therapies for inherited neuromuscular disorders. Practical Neurology [Internet]. Jul/Aug 2021:69-73. Accessed Mar 1, 2022. https://practicalneurology.com/articles/2021-july-aug/genetically-targeted-therapies-for-inherited-neuromuscular-disorders/pdf.

40. Ojala KS et al. In search of a cure: The development of therapeutics to alter the progression of spinal muscular atrophy. Brain Sci. 2021;11(2):194. doi:10.3390/brainsci11020194.

41. McCall S. Cure SMA Releases Updated Drug Pipeline. Cure SMA. Published December 13, 2021. Accessed August 21, 2022. https://www.curesma.org/cure-sma-releases-updated-drug-pipeline- 2021/ 42. FDA approves first drug for spinal muscular atrophy. U.S. Food and Drug Administration. News release. Dec 23, 2016. Accessed Mar 1, 2022. http://www.fda.gov/news-events/press-announcements/fda-approves-first-drug-spinal-muscular-atrophy.43. Kirschner J. Postnatal gene therapy for neuromuscular diseases – Opportunities and limitations. J Perinat Med. 2021 Sep;49(8):1011-5. doi:10.1515/jpm-2021-0435.

43. Terryn J, Verfaillie CM, Van Damme P. Tweaking Progranulin Expression: Therapeutic Avenues and Opportunities. Front Mol Neurosci. 2021;14. Accessed September 4, 2022. https://www.frontiersin.org/articles/10.3389/fnmol.2021.71303144.

44. Biogen. A phase 3, randomized, double-blind, sham-procedure controlled study to assess the clinical efficacy and safety of ISIS 396443 administered intrathecally in patients with later-onset spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT02292537. Updated Feb 17, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/study/NCT02292537.

45. Why Spinraza/later-onset studies. SPINRAZA® (nusinersen) [Internet]. Accessed Mar 1, 2022. www.spinraza.com/en_us/home/why-spinraza/later-onset-studies.html#scroll-tabs.

46. Biogen. A Phase 3, Randomized, Double-Blind, Sham-Procedure Controlled Study to Assess the Clinical Efficacy and Safety of ISIS 396443 Administered Intrathecally in Patients With Infantile- Onset Spinal Muscular Atrophy. clinicaltrials.gov; 2021. Accessed February 10, 2022. https://clinicaltrials.gov/ct2/show/results/NCT02193074

47. Early-onset SMA (Type 1) | SPINRAZA® (nusinersen). Accessed Mar 1, 2022. https://www.spinraza-hcp.com/en_us/home/why-spinraza/about-spinraza.html.

48. Finkel RS et al; ENDEAR Study Group. Nusinersen versus sham control in infantile-onset spinal muscular atrophy. N Engl J Med. 2017;377(18):1723-32. doi: 10.1056/NEJMoa1702752.

49. Biogen. An open-label study to assess the efficacy, safety, tolerability, and pharmacokinetics of multiple doses of ISIS 396443 delivered intrathecally to subjects with genetically diagnosed and presymptomatic spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT02386553. Updated Nov 18, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT02386553.

50. De Vivo DC et al; NURTURE Study Group. Nusinersen initiated in infants during the presymptomatic stage of spinal muscular atrophy: In-terim efficacy and safety results from the phase 2 NURTURE study. Neuromuscul Disord. 2019 Nov;29(11):842-56. doi:10.1016/j.nmd.2019.09.007.

51. Why Spinraza/presymptomatic study. SPINRAZA® (nusinersen) [Internet]. Accessed Feb 22, 2022. www.spinraza.com/en_us/home/why-spinraza/presymptomatic-study.html#scroll-tabs.

52. FDA approves oral treatment for spinal muscular atrophy. U.S. Food and Drug Administration. News release. Aug 7, 2020. Accessed Mar 1, 2022. http://www.fda.gov/news-events/press-announcements/fda-approves-oral-treatment-spinal-muscular-atrophy.

53. Hoffmann-La Roche. A two-part seamless, open-label, multicenter study to investigate the safety, tolerability, pharmacokinetics, pharmaco-dynamics and efficacy of risdiplam (RO7034067) in infants with type 1 spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT02913482. Updated Jan 21, 2022. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT02913482.

54. Hoffmann-La Roche. A two-part seamless, multi-center randomized, placebo-controlled, double-blind study to investigate the safety, tolera-bility, pharmacokinetics, pharmacodynamics and efficacy of risdiplam (RO7034067) in type 2 and 3 spinal muscular atrophy patients. Clinical-Trials.gov Identifier: NCT02908685. Updated Dec 28, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT02908685.

55. Genentech. Genentech’s risdiplam shows significant improvement in survival and motor milestones in infants with type 1 spinal muscular atrophy (SMA). Press release. Apr 27, 2020. Accessed Mar 1, 2022. http://www.gene.com/media/press-releases/14847/2020-04-27/genentechs-risdiplam-shows-significant-i

56. Hoffmann-La Roche. An open-label study to investigate the safety, tolerability, and pharmacokinetics/pharmacodynamics of risdiplam (RO7034067) in adult and pediatric patients with spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT03032172. Updated Jan 27, 2022. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT03032172.

57. Hoffmann-La Roche. An open-label study of risdiplam in infants with genetically diagnosed and presymptomatic spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT03779334. Updated Jan 27, 2022. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT03779334.

58. McCall S. Update on Genentech/Roche Initiation of MANATEE Clinical Study. Cure SMA. Published October 20, 2021. Accessed August 20, 2022. https://www.curesma.org/update-on- genentech-roche-initiation-of-manatee-clinical-study/

59. Abati E, Manini A, Comi GP, Corti S. Inhibition of myostatin and related signaling pathways for the treatment of muscle atrophy in motor neuron diseases. Cell Mol Life Sci. 2022;79(7):374. doi:10.1007/s00018-022-04408-w

60. FDA approves innovative gene therapy to treat pediatric patients with spinal muscular atrophy, a rare disease and leading genetic cause of infant mortality. U.S. Food and Drug Administration. News release. May 24, 2019. Accessed Mar 1, 2022. http://www.fda.gov/news-events/press-announcements/fda-approves-innovative-gene-therapy-treat-pediatric-patients-spinal-muscular-atrophy-rare-disease.

61. Novartis Gene Therapies. Phase I gene transfer clinical trial for spinal muscular atrophy type 1 delivering AVXS-101. ClinicalTrials.gov Identifier: NCT02122952. Updated Jun 14, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT02122952.

62. Novartis Gene Therapies. Phase 3, open-label, single-arm, single-dose gene replacement therapy clinical trial for patients with spinal mus-cular atrophy type 1 with one or two SMN2 copies delivering AVXS-101 by intravenous infusion. ClinicalTrials.gov Identifier: NCT03306277. Updated Jun 14, 2021. Accessed Feb 21, 2022. https://clinicaltrials.gov/ct2/show/NCT03306277.

63. Mendell JR et al. Single-dose gene-replacement therapy for spinal muscular atrophy. N Engl J Med. 2017;377(18):1713-22. doi:10.1056/NEJMoa1706198.

64. Symptomatic study results. ZOLGENSMA [Internet]. Updated Nov 2021. Accessed Mar 1, 2022. Error! Hyperlink reference not valid..

65. Novartis Gene Therapies. A global study of a single, one-time dose of AVXS-101 delivered to infants with genetically diagnosed and pre-symptomatic spinal muscular atrophy with multiple copies of SMN2. ClinicalTrials.gov Identifier: NCT03505099. Updated Jan 1, 2022. Ac-cessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT03505099.

66. Chiu W et al. Current genetics and potential gene-targeting therapeutics for neuromuscular diseases. Int J Mol Sci. 2020 Dec;21(24):9589. doi:10.3390/ijms21249589.

67. Novartis Gene Therapies. A long-term follow-up study of patients in the clinical trials for spinal muscular atrophy receiving AVXS-101. Clini-calTrials.gov Identifier: NCT04042025. Updated Jun 9, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT04042025.

68. Novartis Gene Therapies. Phase 3, open-label, single-arm, single-dose gene replacement therapy clinical trial for patients with spinal mus-cular atrophy type 1 with one or two SMN2 copies delivering AVXS-101 by intravenous infusion. ClinicalTrials.gov Identifier: NCT0383718. Up-dated Jan 11, 2022. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT03837184.

69. Biogen. An open-label, dose escalation study to assess the safety, tolerability and dose-range finding of multiple doses of ISIS 396443 de-livered intrathecally to patients with spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT01703988. Updated Apr 13, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT01703988.

70. Biogen. A study to assess the efficacy, safety, tolerability, and pharmacokinetics of multiple doses of ISIS 396443 delivered intrathecally to patients with infantile-onset spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT01839656. Updated Feb 17, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT01839656.

71. Biogen. An open-label extension study for patients with spinal muscular atrophy who previously participated in investigational studies of ISIS 396443. ClinicalTrials.gov Identifier: NCT02594124. Updated Nov 15, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT02594124.

72. Biogen. Escalating dose and randomized, controlled study of nusinersen (BIIB058) in participants with spinal muscular atrophy. ClinicalTri-als.gov Identifier: NCT04089566. Updated Feb 24, 2022. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT04089566.

73. National Center for Advancing Translational Sciences. Duchenne muscular dystrophy. Genetic and Rare Diseases Information Center. Up-dated Nov 2, 2020. Accessed Mar 1, 2022. https://rarediseases.info.nih.gov/diseases/6291/duchenne-muscular-dystrophy.

74. Matsuo M. Antisense oligonucleotide-mediated exon-skipping therapies: Precision medicine spreading from Duchenne muscular dystrophy. JMA J. 2021 Jul 15;4(3):232-40. doi:10.31662/jmaj.2021-0019.

75. FDA approves drug to treat Duchenne muscular dystrophy. U.S. Food and Drug Administration. News release. Feb 9, 2017. Accessed Mar 1, 2022. http://www.fda.gov/news-events/press-announcements/fda-approves-drug-treat-duchenne-muscular-dystrophy.74.

76. Duan D. Dystrophin gene replacement and gene repair therapy for Duchenne muscular dystrophy in 2016: An interview. Hum Gene Ther Clin Dev. 2016 Mar;27(1):9-18. doi:10.1089/humc.2016.001.

77. EXONDYS 51®. Parent Project Muscular Dystrophy. Accessed August 21, 2022. https://www.parentprojectmd.org/drug-development-pipeline/exondys-51/

78. Sarepta Therapeutics, Inc. A Randomized, Double-Blind, Placebo-Controlled, Multiple Dose Efficacy, Safety, Tolerability and Pharmacoki-netics Study of AVI-4658(Eteplirsen),in the Treatment of Ambulant Subjects With Duchenne Muscular Dystrophy. clinicaltrials.gov; 2020. Ac-cessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT01396239

79. Sarepta Therapeutics, Inc. Clinical Study to Assess the Safety Fo AVI-4658 in Subjects With Duchenne Muscular Dystrophy Due to a Frame-Shift Mutation Amenable to Correction by Skipping Exon 51. clinicaltrials.gov; 2015. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/study/NCT00844597

80. Sarepta Therapeutics, Inc. A 2-part, randomized, double-blind, placebo-controlled, dose-titration, safety, tolerability, and pharmacokinetics study (Part 1) followed by an open-label efficacy and safety evaluation (Part 2) of SRP-4053 in patients with Duchenne muscular dystrophy amenable to exon 53 skipping. ClinicalTrials.gov Identifier: NCT02310906. Updated Oct 19, 2020. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/results/NCT02310906.

81. Commissioner O of the. FDA grants accelerated approval to first drug for Duchenne muscular dystrophy. FDA. Published March 24, 2020. Accessed August 21, 2022. hDuchenne Muscular Dystrophy Amenable to Exon 51-Skipping Treatment. clinicaltrials.gov; 2022. Accessed Au-gust 18, 2022. https://clinicaltrials.gov/ct2/show/NCT04004065

109. National Center of Neurology and Psychiatry, Japan. Exploratory study of NS-065/NCNP-01 in Duchenne muscular dystrophy. ClinicalTri-als.gov Identifier: NCT02081625; Updated Feb 26, 2020. Accessed Mar 2, 2022. https://clinicaltrialsttps://www.fda.gov/news-events/press-announcements/fda-grants-accelerated-approval-first-drug-duchenne-muscular- dys-trophy

82. Duchenne Drug Development Pipeline. Parent Project Muscular Dystrophy. Accessed August 21, 2022. https://www.parentprojectmd.org/duchenne-drug-development-pipeline/

83. Sarepta Therapeutics Provides Update on SRP-5051 for the Treatment of Duchenne Muscular Dystrophy | Sarepta Therapeutics, Inc. Ac-cessed August 22, 2022. https://investorrelations.sarepta.com/news-releases/news-release-details/sarepta-therapeutics- pro-vides-update-srp-5051-treatment-duchenne

84. Sarepta Therapeutics, Inc. An Open-Label Extension Study for Patients With Duchenne Muscular Dystrophy Who Participated in Studies of SRP-5051. clinicaltrials.gov; 2021. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT03675126

85. VYONDYS 53. Prescribing information. Sarepta Therapeutics Inc.; 2019. Accessed Mar 2, 2022. http://www.accessdata.fda.gov/drugsatfda_docs/label/2019/211970s000lbl.pdf.

86. NS Pharma Inc. Long-term use of viltolarsen in boys with Duchenne muscular dystrophy in clinical practice (VILT-502). ClinicalTrials.gov Identifier: NCT04687020. Updated Nov 22, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT04687020.

87. VILTEPSO. Prescribing information. NS Pharma; 2020. Accessed Mar 2, 2022. http://www.accessdata.fda.gov/drugsatfda_docs/label/2020/212154s000lbl.pdf.

88. FDA approves targeted treatment for rare Duchenne muscular dystrophy mutation. U.S. Food and Drug Administration. News release. Feb 25, 2021. Accessed Mar 1, 2022. http://www.fda.gov/news-events/press-announcements/fda-approves-targeted-treatment-rare-duchenne-muscular-dystrophy-mutation-0.

89. Sarepta Therapeutics Inc. A double-blind, placebo-controlled, multi-center study with an open-label extension to evaluate the efficacy and safety of SRP-4045 and SRP-4053 in patients with Duchenne muscular dystrophy. Clinicaltrials.gov Identifier: NCT02500381. Updated Aug 19, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT02500381.

90. AMONDYS 45. Prescribing information. Sarepta Therapeutics Inc.; 2021. Accessed Feb 22, 2022. http://www.accessdata.fda.gov/drugsatfda_docs/label/2021/213026lbl.pdf.

91. Finkel RS et al. Phase 2a study of ataluren-mediated dystrophin production in patients with nonsense mutation Duchenne muscular dys-trophy. PLoS ONE. 2013;8(12):e81302. doi:10.1371/journal.pone.0081302.

92. PTC Therapeutics. A phase 2 study of PTC124 as an oral treatment for nonsense-mutation-mediated Duchenne muscular dystrophy. Clini-calTrials.gov Identifier: NCT00264888. Updated Jan 14, 2009. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT00264888.

93. PTC Therapeutics. A phase 2B efficacy and safety study of PTC124 in subjects with nonsense-mutation-mediated Duchenne and Becker muscular dystrophy. ClinicalTrials.gov Identifier: NCT00592553. Updated Apr 7, 2020. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT00592553.

94. PTC Therapeutics. A phase 3 efficacy and safety study of ataluren in patients with nonsense mutation dystrophinopathy. ClinicalTrials.gov Identifier: NCT01826487. Updated Aug 4, 2020. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT01826487.

95. Bushby K et al; PTC124-GD-007-DMD Study Group. Ataluren treatment of patients with nonsense mutation dystrophinopathy. Muscle Nerve. 2014 Oct;50(4):477-87. doi:10.1002/mus.24332.

96. Solid Biosciences LLC. A randomized, controlled, open-label, single-ascending dose, phase I/II study to investigate the safety and tolerabil-ity, and efficacy of intravenous SGT-001 in male adolescents and children with Duchenne muscular dystrophy. ClinicalTrials.gov Identifier: NCT03368742. Updated Aug 24, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT03368742.

97. Solid Biosciences reports 1.5-year data from patients in the ongoing IGNITE DMD phase I/II clinical trial of SGT-001. Press release. Solid Biosciences. Sep 27, 2021. Accessed Mar 2, 2022. http://www.solidbio.com/about/media/press-releases/solid-biosciences-reports-1-5-year-data-from-patients-in-the-ongoing-ignite-dmd-phase-i-ii-clinical-trial-of-sgt-001.

98. Potter RA et al. Dose-escalation study of systemically delivered rAAVrh74.MHCK7.microdystrophin in the mdx mouse model of Duchenne muscular dystrophy. Hum Gene Ther. 2021 Apr;32(7-8):375-89. doi:10.1089/hum.2019.255.

99. Sarepta Therapeutics, Inc. A Phase 3 Multinational, Randomized, Double-Blind, Placebo- Controlled Systemic Gene Delivery Study to Evaluate the Safety and Efficacy of SRP-9001 in Patients With Duchenne Muscular Dystrophy (EMBARK). clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT05096221

100. Pfizer. A PHASE 3, MULTICENTER, RANDOMIZED, DOUBLE-BLIND, PLACEBO CONTROLLED STUDY TO EVALUATE THE SAFETY AND EFFICACY OF PF 06939926 FOR THE TREATMENT OF DUCHENNE MUSCULAR DYSTROPHY. clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT04281485

101. Pfizer. A phase 1B multicenter open-label, single ascending dose study to evaluate the safety and tolerability of PF-06939926 in ambula-tory and non-ambulatory subjects with Duchenne muscular dystrophy. ClinicalTrials.gov Identifier: NCT03362502. Updated Mar 2, 2022. Ac-cessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT03362502.

102. MS MW. Phase 3 CIFFREO DMD Gene Therapy Trial Slated to Begin in June in US. Accessed August 21, 2022. https://musculardystrophynews.com/news/phase-3-trial-of-pfizers-gene-therapy- expected-to-open-in-us-in-june/

103. SRP-9001. Parent Project Muscular Dystrophy. Accessed August 22, 2022. https://www.parentprojectmd.org/drug-development-pipeline/srp-9001-micro-dystrophin-gene- transfer/

104. Sarepta Therapeutics’ Investigational Gene Therapy SRP-9001 for Duchenne Muscular Dystrophy Demonstrates Significant Functional Improvements Across Multiple Studies | Sarepta Therapeutics, Inc. Accessed August 22, 2022. https://investorrelations.sarepta.com/news-releases/news-release- details/sarepta-therapeutics-investigational-gene-therapy-srp-9001

105. Sarepta Therapeutics, Inc. An Open-Label Safety, Tolerability, and Efficacy Study of Eteplirsen in Patients With Duchenne Muscular Dys-trophy Who Have Completed Study 4658-102.clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT03985878

106. Sarepta Therapeutics, Inc. An Open-Label Safety, Tolerability, and Pharmacokinetics Study of Eteplirsen in Young Patients With Duchenne Mus-cular Dystrophy Amenable to Exon 51 Skipping. clinicaltrials.gov; 2021. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT03218995

107.Sarepta Therapeutics, Inc. A Randomized, Double-Blind, Dose Finding and Comparison Study of the Safety and Efficacy of a High Dose of Eteplirsen, Preceded by an Open-Label Dose Escalation, in Patients With Duchenne Muscular Dystrophy With Deletion Mutations Amenable to Exon 51 Skipping. clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT03992430

108. Sarepta Therapeutics, Inc. A Phase 2, Two-Part, Multiple-Ascending-Dose Study of SRP-5051 for Dose Determination, Then Dose Ex-pansion, in Patients With .gov/ct2/show/NCT02081625.

110. NS Pharma Inc. A phase II, dose finding study to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics of NS-065/NCNP-01 in boys with Duchenne muscular dystrophy (DMD). ClinicalTrials.gov Identifier: NCT02740972. Updated Dec 7, 2021. Ac-cessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT02740972.

111. NS Pharma Inc. A phase II, open-label, extension study to assess the safety and efficacy of NS-065/NCNP-01 in boys with Duchenne muscular dystrophy (DMD). ClinicalTrials.gov Identifier: NCT03167255. Updated Nov 24, 2021. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT03167255.

112. NS Pharma Inc. A phase 2 open label study to assess the safety, tolerability, and efficacy of viltolarsen in ambulant and non-ambulant boys with Duchenne muscular dystrophy (DMD) compared with natural history controls. ClinicalTrials.gov Identifier: NCT04956289. Updated Feb 1, 2022. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT04956289.

113. NS Pharma Inc. A phase 3 randomized, double-blind, placebo-controlled, multi-center study to assess the efficacy and safety of viltolarsen in ambulant boys with Duchenne muscular dystrophy (DMD). ClinicalTrials.gov Identifier: NCT04060199. Updated Nov 16, 2021. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT04060199.

114. NS Pharma Inc. A phase 3, multi-center, open-label extension study to assess the safety and efficacy of viltolarsen in ambulant boys with Duchenne muscular dystrophy (DMD). ClinicalTrials.gov Identifier: NCT04768062. Updated Nov 16, 2021. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT04768062.

115. Sarepta Therapeutics Inc. A randomized, double-blind, placebo-controlled, dose-titration, safety, tolerability, and pharmacokinetics study followed by an open-label safety and efficacy evaluation of SRP-4045 in advanced-stage patients with Duchenne muscular dystrophy amena-ble to exon 45 skipping. ClinicalTrials.gov Identifier: NCT02530905. Updated May 17, 2021. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT02530905.

116. Sarepta Therapeutics Inc. Long-term, open-label extension study for patients with Duchenne muscular dystrophy enrolled in clinical trials evaluating casimersen or golodirsen. ClinicalTrials.gov Identifier: NCT03532542. Updated Dec 20, 2021. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT03532542.

117. PTC Therapeutics. A phase 2 study of the safety, pharmacokinetics, and pharmacodynamics of ataluren (PTC124®) in patients aged ≥2 to <5 years old with nonsense mutation dystrophinopathy. ClinicalTrials.gov Identifier: NCT02819557. Updated Aug 28, 2020. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT02819557.

118. PTC Therapeutics. Phase 2, non-interventional, clinical study to assess dystrophin levels in subjects with nonsense mutation Duchenne muscular dystrophy who have been treated with ataluren for ≥ 9 months. ClinicalTrials.gov Identifier: NCT03796637. Updated Apr 10, 2020. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT03796637.

119. PTC Therapeutics. An Open-Label Study Evaluating the Safety and Pharmacokinetics of Ataluren in Children From ≥6 Months to <2 Years of Age With Nonsense Mutation Duchenne Muscular Dystrophy. clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT04336826 120. PTC Therapeutics. An open-label study for previously treated ataluren (PTC124®) pa-tients with nonsense mutation dystrophinopathy. ClinicalTrials.gov Identifier: NCT01557400. Updated Nov 25, 2020. Accessed Feb 21, 2022. https://clinicaltrials.gov/ct2/show/NCT01557400.

121. PTC Therapeutics. An open-label, safety study for ataluren (PTC124) patients with nonsense mutation dystrophinopathy. ClinicalTrials.gov Identifier: NCT01247207. Updated Feb 16, 2022. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT01247207.

122. PTC Therapeutics. A phase 3, randomized, double-blind, placebo-controlled efficacy and safety study of ataluren in patients with non-sense mutation Duchenne muscular dystrophy and open-label extension. ClinicalTrials.gov Identifier: NCT03179631. Updated Feb 8, 2022. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT03179631.

123. Sarepta Therapeutics, Inc. An Open-Label, Systemic Gene Delivery Study Using Commercial Process Material to Evaluate the Safety of and Expression From SRP-9001 in Subjects With Duchenne Muscular Dystrophy (ENDEAVOR). clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT04626674

124. Sarepta Therapeutics, Inc. Systemic Gene Delivery Phase I/IIa Clinical Trial for Duchenne Muscular Dystrophy Using RAA-Vrh74.MHCK7.Micro-Dystrophin (MicroDys-IV-001). clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT03375164

125. Sarepta Therapeutics Inc. A multicenter, randomized, double-blind, placebo-controlled trial for Duchenne muscular dystrophy using SRP-9001. ClinicalTrials.gov Identifier: NCT03769116. Updated Dec 2021. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT03769116.

126. Hoffmann-La Roche. A Two-Part, Seamless, Multi-Center, Randomized, Placebo-Controlled, Double-Blind Study to Investigate the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics and Efficacy of RO7204239 in Combination With Risdiplam (RO7034067) in Ambulant Pa-tients With Spinal Muscular Atrophy. clinicaltrials.gov; 2022. Accessed September 1, 2022. https://clinicaltrials.gov/ct2/show/NCT05115110

Neuromuscular diseases (NMDs) are a broad classification of heterogeneous groups of disorders characterized by progressive muscle weakness resulting from muscle or nerve dysfunction.¹ Diagnosis is based on symptoms and a full medical history, as well as on muscle and imaging tests (including electromyography, nerve-conduction studies, magnetic resonance imaging, muscle biopsy, and blood tests) to confirm or rule out specific NMDs.² Early diagnosis of NMDs can be difficult because symptoms overlap with those of many other diseases.

Although individually, NMDs are rare, collectively, they affect approximately 250,000 people in the United States. Disease types vary in regard to cause, symptoms, prevalence, age of onset, progression, and severity. Functional impairment from any NMD can lead to lifelong morbidities and shortened life expectancy.^1,3

Treatment options for NMDs are limited; most target symptoms, not disease progression. Although there is a need for safe and effective gene-based therapies for NMDs, there are challenges to developing and delivering such treatments that have impeded clinical success. These include a lack of understanding about disease pathology and drug targets, limited animal model systems, and few reliable biomarkers that are predictive of therapeutic success.^4,5

Amyotrophic lateral sclerosis

ALS is caused by progressive degeneration of upper- and lower-motor neurons, which eventually leads to respiratory failure and death 3 to 5 years after disease onset.^7-9 There are two subtypes: Familial ALS (10% of cases) and sporadic ALS (90% of cases). Commonly mutated ALS-associated genes^6,8 are:

• Superoxide dismutase type 1 (SOD1).
• Chromosome 9 open reading frame 72 (C9orf72).
• Transactive response DNA-binding protein 43 (TARDBP).
• Fused in sarcoma (FUS).

SOD1-targeted therapy is being studied, with early evidence of clinical success. Mutations in SOD1 account for 10% to 20% of familial ALS cases and 1% to 2% of sporadic ALS cases.^6,10 10 Mutations in C9orf72 account for 25 to 40% of familial ALS cases and 7% of sporadic ALS cases.^8,9,11 Mutations in TARDBP account for 3% of familial ALS cases and 2% of sporadic cases.¹² Mutations in FUS account for 4% of familial ALS cases and 1% of sporadic cases. Overall, these mutant proteins can trigger neurotoxicity, thus inducing motor-neuron death.^6,10
 

Treatment of ALS

Two treatments for ALS are Food and Drug Administration approved: riluzole (Rilutek), approved in 1995, and edaravone (Radicava), approved in 2017.

Riluzole is an oral anti-excitotoxic glutamate antagonist.¹¹ Approval of riluzole was based on the results of two studies that demonstrated a 2- to 3-month survival benefit.^10,14 For patients who have difficulty swallowing, an oral suspension (Tiglutik, approved in 2018) and an oral film (Exservan, approved in 2019) are available.

Edaravone is a free-radical scavenger that decreases oxidative stress and is administered intravenously (IV).^9,13,14 Findings from clinical trials suggest functional improvement or slower decline in function for some patients.

Although these two agents demonstrate modest therapeutic benefit, neither reverses progression of disease.^10,14
 

Gene-based therapy for ALS

Many non-viral strategies, including antisense oligonucleotide (ASO), monoclonal antibodies, reverse transcriptase inhibitors, and HGF gene replacement therapy are used as therapeutic approaches to SOD1, C9orf72, and FUS gene mutations in ALS patients, and are being evaluated in clinical studies^14,15 (Table 1^13-17).

• Change from baseline in CSF SOD1 protein concentration.¹⁷ Percent reduction in the total SOD1 protein level was much higher in the tofersen-treated group than in the control group (38% more than controls in the faster-progressing population; 26% more than controls in the slower-progressing population).¹⁸
• Change from baseline in neurofilament light-chain concentration in plasma.^17,18 Percent reduction in the level of neurofilament light chain was also observed to be higher in the tofersen-treated group than in the control group (67% more than controls in the faster-progressing population and 48% more than controls in the slower-progressing population).¹⁸

Because of these encouraging results, VALOR participants were moved to the ongoing open-label extension trial of tofersen (ClinicalTri-als.gov Identifier: NCT03070119), in which both groups were treated with the active agent.

These data suggest that early tofersen treatment might slow decline in faster-progressing patients and stabilize clinical function in slower-progressing patients.^18,19 Overall, most adverse events (AEs) in the trial among patients receiving active treatment were of mild or moderate severity, and were largely consistent with either disease progression or lumbar puncture–related complications.¹⁸

Because data from VALOR suggested potential benefit from tofersen, the ATLAS trial (ClinicalTrials.gov Identifier: NCT04856982) is investigating the clinical value of presymptomatic treatment and the optimal timing of initiation of therapy.^20,21 ATLAS is a phase 3, randomized, placebo-controlled trial that examines the clinical efficacy, safety, and tolerability of tofersen in presymptomatic adult carriers of SOD1 mutation who have an elevated neurofilament light-chain concentration.²¹ ATLAS will also evaluate the efficacy of tofersen when initiated before, rather than after, ALS manifests clinically. Enrollment is still open for this trial.^20,21

Latozinemab, also known as AL001, is a first-in-class monoclonal antibody, administered by IV infusion, that elevates levels of progranulin, a key regulator of the immune activity and lysosomal function in the brain.^22,23 Latozinemab limits progranulin endocytosis and degradation by sortilin inhibition.²² Progranulin gene mutations can reduce progranulin expression (by 50 to 70 percent reduction), which may cause neuro-degeneration due to abnormal accumulation of TAR-DNA-binding protein 43 (TDP-43) in the brain cells.^22,24 TDP-43 pathology has also been shown to be associated with C9orf72 mutations.²³ Although the mechanism is not fully understood, the role of progranulin deficiency in TDP-43 pathology is believed to be associated with neurodegenerative diseases like ALS.11,23,24,43 Previous animal models of chronic neurodegenera-tion have demonstrated how increased progranulin levels can be protective against TDP-43 pathology, increasing neuronal development and survival, thus potentially slowing disease progression.^23,24,43 Currently, latozinemab is being investigated in a randomized, double-blind, placebo-controlled, multicenter phase 2 trial (ClinicalTrials.gov Identifier: NCT05053035). Approximately, 45 C90rf72-associated ALS participants (≥ 18 years of age) will receive latozinemab or placebo infusions every 4 weeks (for 24 weeks). Study endpoints include safety, tolerability, PK, PD, as well as plasma, and CSF progranulin levels.²⁵ In previous studies, latozinemab demonstrated encouraging results in frontotemporal dementia (FTD) patients who carry a progranulin mutation. Because FTD was revealed to have significant genetic overlap with ALS, there is disease-modifying potential for latozinemab in ALS patients.^23,24

TPN-101 is a nucleoside analog reverse transcriptase inhibitor, administered orally, that was originally developed for human immunodeficiency virus (HIV) treatment. However, due to recent findings suggesting retrotransposon activity contributing to neurodegeneration in TDP-43 mediated diseases, including ALS and FTD, TNP-101 is being repurposed.²⁶ The safety and tolerability of TNP-101 are currently being evaluated in C9orf72-associated ALS and FTD patients (≥ 18 years of age). The study is a randomized, double-blind, placebo-controlled paral-lel-group phase 2a trial (ClinicalTrials.gov Identifier: NCT04993755) The study includes a screening period of 6 weeks, double-blind treatment period of 24 weeks, an open-label treatment period of 24 weeks, and 4 weeks of the post-treatment follow-up visit. Study endpoints include the incidence and severity of spontaneously reported treatment-emergent adverse events (TEAEs) associated with TNP-101 and placebo for a to-tal of 48 weeks.²⁷

ION363 is an investigational ASO, administered by IT injection, that selectively targets one of the FUS mutations (p.P525L), which is responsible for earlier disease onset and rapid ALS progression.^28,29 The clinical efficacy of ION363, specifically in clinical function and survival is being assessed in FUS-associated ALS patients (≥ 12 years of age). This randomized phase 3 study (ClinicalTrials.gov Identifier: NCT04768972) includes two parts; part 1 will consist of participants receiving a multi-dose regimen (1 dose every 4-12 weeks) of ION363 or placebo for 61 weeks followed by an open-label extension treatment period in part 2, which will consist of participants receiving ION363 (every 12 weeks) for 85 weeks. The primary endpoint of the study is the change from baseline to day 505 in functional impairment, using ALS Functional Rating Scale-Revised (ALSFRS-R). This measures functional disease severity, specifically in bulbar function, gross motor skills, fine motor skills, and respiratory. The score for all 12 questions can range from 0 (no function) to 4 (full function) with a total possible score of 48.³⁰

Engensis, also known as VM202, is a non-viral gene therapy, administered by intramuscular (IM) injection, that uses a plasmid to deliver the hepatocyte growth factor (HGF) gene to promote HGF protein production. The HGF protein plays a role in angiogenesis, the previous of muscle atrophy, and the promotion of neuronal survival and growth. Based on preclinical studies, increasing HGF protein production has been shown to reduce neurodegeneration, thus potentially halting or slowing ALS progression.³¹ Currently, the safety of engensis is being evaluated in ALS patients (18-80 years of age) in the REViVALS phase 2a (ClinicalTrials.gov Identifier: NCT04632225)/2b (ClinicalTrial.gov Identifier: NCT05176093).^32,33 The ReViVALS trial is a double-blind, randomized, placebo-controlled, multi-center study. The phase 2a study endpoints include the incidence of TEAEs, treatment-emergent serious adverse events (TESAEs), injection site reactions, and clinically significant labor-atory values post-treatment (engensis vs placebo group) for 180 days.³³ A phase 2b study will evaluate the long-term safety of engensis for an additional 6 months. Study endpoints include the incidence of AEs, changes from baseline in ALSFRS-R scores to evaluate improvement in muscle function, changes from baseline in quality of life using the ALS patient assessment questionnaire, time to all-cause mortality compared to placebo, etc.³²
 

Spinal muscular atrophy

SMA is a hereditary lower motor-neuron disease caused (in 95% of cases) by deletions or, less commonly, by mutations of the survival motor neuron 1 (SMN1) gene on chromosome 5q13 that encodes the SMN protein.⁶ Reduction in expression of the SMN protein causes motor neurons to degenerate.^36-38 Because of a large inverted duplication in chromosome 5q, two variants of SMN (SMN1 and SMN2) exist on each allele. The paralog gene, SMN2, also produces the SMN protein – although at a lower level (10% to 20% of total SMN protein production) than SMN1 does.

A single nucleotide substitution in SMN2 alters splicing and suppresses transcription of exon 7, resulting in a shortened mRNA strand that yields a truncated SMN protein product.^6,37,39 SMA is classified based on age of onset and maximum motor abilities achieved, ranging from the most severe (Type 0) to mildest (Type 4) disease.^36,40 Because SMA patients lack functional SMN1 (due to polymorphisms), disease severity is determined by copy numbers of SMN2.^6,39

 

Gene-based therapy for SMA

Three FDA-approved SMN treatments demonstrate clinically meaningful benefit in SMA: SMN2-targeting nusinersen [Spinraza] and risdiplam [Evrysdi], and SMN1-targeting onasemnogene abeparvovec-xioi [Zolgensma]³⁸ Additional approaches to SMA treatment are through SMN-independent therapies, which target muscle and nerve function. Research has strongly suggested that combined SMA therapies, specifically approved SMN-targeted and investigational SMN-independent treatments, such as GYM329 (also known as RO7204239) may be the best strategy to treat all ages, stages, and types of SMA.⁴¹ (Table 2^26-41).

• Percentage of motor milestones responders, as determined using Section 2 of the Hammersmith Infant Neurological Examination–Part 2.
• Event-free survival (that is, avoidance of combined endpoint of death or permanent ventilation).

ENDEAR met the first primary efficacy outcome, demonstrating statistically significant (P < .0001) improvement in motor milestones (head control, rolling, independent sitting, and standing). By 13 months of age, approximately 51% of nusinersen-treated participants showed improvement, compared with none in the control group.^46,47

The second primary endpoint was also met, with a statistically significant (P = .005) 47% decrease in mortality or permanent ventilation use.^46-48

The NURTURE (ClinicalTrial.gov Identifier: NCT02386553) study is also investigating the efficacy and safety of nusinersen. An ongoing, open-label, supportive phase 2 trial, NURTURE is evaluating the efficacy and safety of multiple doses of nusinersen in 25 presymptomatic SMA patients (≤ 6 weeks of age). The primary endpoint of this study is time to death or respiratory intervention.⁴⁹ Interim results demonstrate that 100% of presymptomatic infants are functioning without respiratory intervention after median follow-up of 2.9 years.^46-48

Although nusinersen has been shown to be generally safe in clinical studies, development of lumbar puncture–related complications, as well as the need for sedation during IT administration, might affect treatment tolerability in some patients.³⁹

Risdiplam was approved by the FDA in 2020 as the first orally administered small-molecule treatment of SMA (for patients ≤ 2 months of age).⁵² Risdiplam is a SMN2 splicing modifier, binding to the 5’ splice site of intron 7 and exonic splicing enhancer 2 in exon 7 of SMN2 pre-mRNA. This alternative splicing increases efficiency in SMN2 gene transcription, thus increasing SMN protein production in motor-neuron cells.³⁶ An important advantage of risdiplam is the convenience of oral administration: A large percentage of SMA patients (that is, those with Type 2 disease) have severe scoliosis, which can further complicate therapy or deter patients from using a treatment that is administered through the IT route.⁴⁰

FDA approval of risdiplam was based on clinical data from two pivotal studies, FIREFISH (ClinicalTrial.gov Identifier: NCT02913482) and SUNFISH (ClinicalTrial.gov Identifier: NCT02908685).^53-54

FIREFISH is an open-label, phase 2/3 ongoing trial in infants (1-7 months of age) with SMA Type 1. The study comprises two parts; Part 1 determined the dose of risdiplam used in Part 2, which assessed the efficacy and safety of risdiplam for 24 months. The primary endpoint was the percentage of infants sitting without support for 5 seconds after 12 months of treatment using the gross motor scale of the Bayley Scales of Infant and Toddler Development–Third Edition. A statistically significant (P < .0001) therapeutic benefit was observed in motor milestones. Approximately 29% of infants achieved the motor milestone of independent sitting for 5 seconds, which had not been observed in the natural history of SMA.^53-55

SUNFISH is an ongoing randomized, double-blind, placebo-controlled trial of risdiplam in adult and pediatric patients with SMA Types 2 and 3 (2-25 years old). This phase 2/3 study comprises two parts: Part 1 determined the dose (for 12 weeks) to be used for confirmatory Part 2 (for 12 to 24 months). The primary endpoint was the change from baseline on the 32-item Motor Function Measure at 12 months. The study met its primary endpoint, demonstrating statistically significant (P = .0156) improvement in motor function scores, with a 1.36-point increase in the risdiplam group, compared with a 0.19-point decrease in the control group.^54,55

Ongoing risdiplam clinical trials also include JEWELFISH (ClinicalTrial.gov Identifier: NCT03032172) and RAINBOW (ClinicalTrial.gov Identifier: NCT03779334).^56-57 JEWELFISH is an open-label, phase 2 trial assessing the safety of risdiplam in patients (6 months to 60 years old) who received prior treatment. The study has completed recruitment; results are pending.⁵⁶ RAINBOW is an ongoing, open-label, single-arm, phase 2 trial, evaluating the clinical efficacy and safety of risdiplam in SMA-presymptomatic newborns (≤ 6 weeks old). The study is open for enrollment.⁵⁷ Overall, interim results for JEWELFISH and RAINBOW appear promising.

In addition, combined SMA therapies, specifically risdiplam and GYM329 are currently being investigated to address the underlying cause and symptoms of SMA concurrently.⁵⁸ GYM329, is an investigational anti-myostatin antibody, selectively binding preforms of myostatin - pro-myostatin and latent myostatin, thus improving muscle mass and strength for SMA patients.⁵⁹ The safety and efficacy of GYM329 in combination with risdiplam is currently being investigated in 180 ambulant participants with SMA (2-10 years of age) in the MANATEE (ClinicalTrial.gov Identifier: NCT05115110) phase 2/3 trial. The MANATEE study is a two-part, seamless, randomized, placebo-controlled, double-blind trial. Part 1 will assess the safety of the combination treatment in approximately 36 participants; participants will receive both GYM329 (every 4 weeks) by subcutaneous (SC) injection into the abdomen and risdiplam (once per day) for 24 weeks followed by a 72-week open-label treatment period. ^54,58 The outcome measures include the incidence of AEs, percentage change from baseline in the contractile area of skeletal muscle (in dominant thigh and calf), change from baseline in RHS total score, and incidence of change from baseline in serum concentration (total myostatin, free latent myostatin, and mature myostatin) etc.⁵⁴ Part 2 will be conducted on 144 participants, specifically assessing the efficacy and safety of the optimal dose of GYM329 selected from Part 1 (combined with risdiplam) for 72 weeks. Once the treatment period is completed in either part, participants can partake in a 2-year open-label extension period.^54,58 Other outcome measures include change from baseline in lean muscle mass (assessed by full body dual-energy X- ray absorptiometry (DXA) scan), in time taken to walk/run 10 meters (measured by RHS), in time taken to rise from the floor (measured by RHS), etc.⁵⁴ Overall, this combination treatment has the potential to further improve SMA patient outcomes and will be further investigated in other patient populations (including non-ambulant patients and a broader age range) in the future.⁵⁸

An agent that alters SMN1 expression. Onasemnogene abeparvovec-xioi, FDA approved in 2019, was the first gene-replacement therapy indicated for treating SMA in children ≤ 2 years old.⁶⁰ Treatment utilizes an AAV vector type 9 (AAV9) to deliver a functional copy of SMN1 into target motor-neuron cells, thus increasing SMN protein production and improving motor function. This AAV serotype is ideal because it crosses the blood-brain barrier. Treatment is administered as a one-time IV fusion.^38,39,43

FDA approval was based on the STR1VE (ClinicalTrial.gov Identifier: NCT03306277) phase 3 study and START (ClinicalTrial.gov Identifier: NCT02122952) phase 1 study.^61,62 START was the first trial to investigate the safety and efficacy of onasemnogene abeparvovec-xioi in SMA Type 1 infants (< 6 months old). Results demonstrated remarkable clinical benefit, including 100% permanent ventilation-free survival and a 92% (11 of 12 patients) rate of improvement in motor function. Improvement in development milestones was also observed: 92% (11 of 12 patients) could sit without support for 5 seconds and 75% (9 of 12) could sit without support for 30 seconds.^14,61,63

The efficacy of onasemnogene abeparvovec-xioi seen in STR1VE was consistent with what was observed in START. STRIVE, a phase 3 open-label, single-dose trial, examined treatment efficacy and safety in 22 symptomatic infants (< 6 months old) with SMA Type 1 (one or two SMN2 copies). The primary endpoint was 30 seconds of independent sitting and event-free survival. Patients were followed for as long as 18 months. Treatment showed statistically significant (P < .0001) improvement in motor milestone development and event-free survival, which had not been observed in SMA Type 1 historically. Approximately 59% (13 of 22 patients) could sit independently for 30 seconds at 18 months of age. At 14 months of age, 91% (20 of 22 patients) were alive and achieved independence from ventilatory support.^34,35,53

Although many clinical studies suggest that onasemnogene abeparvovec-xioi can slow disease progression, the benefits and risks of long-term effects are still unknown. A 15-year observational study is investigating the long-term therapeutic effects and potential complications of onasemnogene abeparvovec-xioi. Participants in START were invited to enroll in this long-term follow-up study (ClinicalTrial.gov Identifier: NCT04042025).^66-67
 

Duchenne muscular dystrophy

DMD is the most common muscular dystrophy of childhood. With an X-linked pattern of inheritance, DMD is seen mostly in young males (1 in every 3,500 male births).^38,39,73 DMD is caused by mutation of the dystrophin encoding gene, or DMD, on the X chromosome. Deletion of one or more exons of DMD prevents production of the dystrophin protein, which leads to muscle degeneration.^38,39,43 Common DMD deletion hotspots are exon 51 (20% of cases), exon 53 (13% of cases), exon 44 (11% of cases), and exon 45 (12% of cases).⁷⁴ Nonsense mutations, which account for another 10% of DMD cases, occur when premature termination codons are found in the DMD gene. Those mutations yield truncated dystrophin protein products.^39,66

Therapy for DMD

There are many therapeutic options for DMD, including deflazacort (Emflaza), FDA approved in 2017, which has been shown to reduce inflammation and immune system activity in DMD patients (≥ 5 years old). Deflazacort is a corticosteroid prodrug; its active metabolite acts on the glucocorticoid receptor to exert anti-inflammatory and immunosuppressive effects. Studies have shown that muscle strength scores over 6-12 months and average time to loss of ambulation numerically favored deflazacort over placebo.^74,75

Gene-based therapy for DMD

Mutation-specific therapeutic approaches, such as exon skipping and nonsense suppression, have shown promise for the treatment of DMD (Table 3^58-79):

• ASO-mediated exon skipping allows one or more exons to be omitted from the mutated DMD mRNA.^74,75 Effective FDA-approved ASOs include golodirsen [Vyondys 53], viltolarsen [Viltepso], and casimersen [Amondys 45].⁷⁴
• An example of therapeutic suppression of nonsense mutations is ataluren [Translarna], an investigational agent that can promote premature termination codon read-through in DMD patients.⁶⁶

Another potential treatment approach is through the use of AAV gene transfer to treat DMD. However, because DMD is too large for the AAV vector (packaging size, 5.0 kb), microdystrophin genes (3.5-4 kb, are used as an alternative to fit into a single AAV vector.^39,76

Exon skipping targeting exon 51. Eteplirsen, approved in 2016, is indicated for the treatment of DMD patients with the confirmed DMD gene mutation that is amenable to exon 51 skipping. Eteplirsen binds to exon 51 of dystrophin pre-mRNA, causing it to be skipped, thus, restoring the reading frame in patients with DMD gene mutation amenable to exon 51 skipping. This exclusion promotes dystrophin production. Though the dystrophin protein is still functional, it is shortened.^38,77 Treatment is administered IV, once a week (over 35-60 minutes). Eteplirsen’s accelerated approval was based on 3 clinical studies (ClinicalTrial.gov Identifier: NCT01396239, NCT01540409, and NCT00844597.) ^78-81 The data demonstrated an increased expression of dystrophin in skeletal muscles in some DMD patients treated with eteplirsen. Though the clinical benefit of eteplirsen (including improved motor function) was not established, it was concluded by the FDA that the data were reasonably likely to predict clinical benefit. Continued approval for this indication may depend on the verification of a clinical benefit in confirmatory trials. Ongoing clinical trials include (ClinicalTrial.gov Identifier: NCT03992430 (MIS51ON), NCT03218995, and NCT03218995).^77,81,82

Vesleteplirsen, is an investigational agent that is designed for DMD patients who are amendable to exon 51 skip-ping. The mechanism of action of vesleteplirsen appears to be similar to that of eteplirsen.⁸³ The ongoing MOMENTUM (ClinicalTrial.gov Identifier: NCT04004065) phase 2 trial is assessing the safety and tolerability of vesleteplirsen at multiple-ascending dose levels (administered via IV infusion) in 60 participants (7-21 years of age). The study consists of two parts; participants receive escalating dose levels of vesleteplirsen (every 4 weeks) for 72 weeks during part A and participants receive the selected doses from part A (every 4 weeks) for 2 years during part B. Study endpoints include the number of AEs (up to 75 weeks) and the change from baseline to week 28 in dystrophin protein level. 84 Serious AEs of reversible hypomagnesemia were observed in part B, and as a result, the study protocol was amended to include magnesium supplementation and monitoring of magnesium levels.⁸³

Exon skipping targeting exon 53. Golodirsen, FDA approved in 2019, is indicated for the treatment of DMD in patients who have a confirmed DMD mutation that is amenable to exon 53 skipping. The mechanism of action is similar to eteplirsen, however, golodirsen is designed to bind to exon 53.^38,39 Treatment is administered by IV infusion over 35-60 minutes.

Approval of golodirsen was based primarily on a two-part, phase 1/2 clinical trial (ClinicalTrial.gov Identifier: NCT02310906). Part 1 was a randomized, placebo-controlled, dose-titration study that assessed multiple-dose efficacy in 12 DMD male patients, 6 to 15 years old, with deletions that were amenable to exon 53 skipping.

Part 2 was an open-label trial in 12 DMD patients from Part 1 of the trial plus 13 newly enrolled male DMD patients who were also amenable to exon 53 skipping and who had not already received treatment. Primary endpoints were change from baseline in total distance walked during the 6-minute walk test at Week 144 and dystrophin protein levels (measured by western blot testing) at Week 48. A statistically significant increase in the mean dystrophin level was observed, from a baseline 0.10% mean dystrophin level to a 1.02% mean dystrophin level after 48 weeks of treatment (P < .001). Common reported adverse events associated with golodirsen were headache, fever, abdominal pain, rash, and dermatitis. Renal toxicity was observed in preclinical studies of golodirsen but not in clinical studies.^80,85

Viltolarsen, approved in 2020, is also indicated for the treatment of DMD in patients with deletions amenable to exon 53 skipping. The mechanism of action and administration (IV infusion over 60 minutes) are similar to that of golodirsen.

Approval of viltolarsen was based on two phase 2 clinical trials (ClinicalTrial.gov Identifier: NCT02740972 and NCT03167255) in a total of 32 patients. NCT02740972 was a randomized, double-blind, placebo-controlled, dose-finding study that evaluated the clinical efficacy of viltolarsen in 16 male DMD patients (4-9 years old) for 24 weeks.

NCT03167255 was an open-label study that evaluated the safety and tolerability of viltolarsen in DMD male patients (5-18 years old) for 192 weeks. The efficacy endpoint was the change in dystrophin production from baseline after 24 weeks of treatment. A statistically significant increase in the mean dystrophin level was observed, from a 0.6% mean dystrophin level at baseline to a 5.9% mean dystrophin level at Week 25 (P = .01). The most common adverse events observed were upper respiratory tract infection, cough, fever, and injection-site reaction.^86-87

Exon skipping targeting exon 45. Casimersen was approved in 2021 for the treatment of DMD in patients with deletions amenable to exon 45 skipping.⁸⁸ Treatment is administered by IV infusion over 30-60 minutes. Approval was based on an increase in dystrophin production in skeletal muscle in treated patients. Clinical benefit was reported in interim results from the ESSENCE (ClinicalTrial.gov Identifier: NCT02500381) study, an ongoing double-blind, placebo-controlled phase 3 trial that is evaluating the efficacy of casimersen, compared with placebo, in male participants (6-13 years old) for 48 weeks. Efficacy is based on the change from baseline dystrophin intensity level, determined by immunohistochemistry, at Week 48.

Interim results from ESSENCE show a statistically significant increase in dystrophin production in the casimersen group, from a 0.9% mean dystrophin level at baseline to a 1.7% mean dystrophin level at Week 48 (P = .004); in the control group, a 0.54% mean dystrophin level at baseline increased to a 0.76% mean dystrophin level at Week 48 (P = .09). Common adverse events have included respiratory tract infection, headache, arthralgia, fever, and oropharyngeal pain. Renal toxicity was observed in preclinical data but not in clinical studies.^60,84

Targeting nonsense mutations. Ataluren is an investigational, orally administered nonsense mutation suppression therapy (through the read-through of stop codons).³⁷ Early clinical evidence supporting the use of ataluren in DMD was seen in an open-label, dose-ranging, phase 2a study (ClinicalTrial.gov Identifier: NCT00264888) in male DMD patients (≥ 5 years old) caused by nonsense mutation. The study demonstrated a modest (61% ) increase in dystrophin expression in 23 of 38 patients after 28 days of treatment.^37,91,92

However, a phase 2b randomized, double-blind, placebo-controlled trial (ClinicalTrial.gov Identifier: NCT00592553) and a subsequent confirmatory ACT DMD phase 3 study (ClinicalTrial.gov Identifier: NCT01826487) did not meet their primary endpoint of improvement in ambulation after 48 weeks as measured by the 6-minute walk test.^37,93,94 In ACT DMD, approximately 74% of the ataluren group did not experience disease progression, compared with 56% of the control group (P = 0386), measured by a change in the 6-minute walk test, which assessed ambulatory decline.^37,95

Based on limited data showing that ataluren is effective and well tolerated, the European Medicines Agency has given conditional approval for clinical use of the drug in Europe. However, ataluren was rejected by the FDA as a candidate therapy for DMD in the United States.²² Late-stage clinical studies of ataluren are ongoing in the United States.

AAV gene transfer with microdystrophin. Limitations on traditional gene-replacement therapy prompted exploration of gene-editing strategies for treating DMD, including using AAV-based vectors to transfer microdystrophin, an engineered version of DMD, into target muscles.⁴³ The microdystrophin gene is designed to produce a functional, truncated form of dystrophin, thus improving muscular function.

There are 3 ongoing investigational microdystrophin gene therapies that are in clinical development (ClinicalTrial.gov Identifier: NCT03368742 (IGNITE DMD), NCT04281485 (CIFFREO), and NCT05096221 (EMBARK)).^38,82

IGNITE DMD is a phase 1/2 randomized, controlled, single-ascending dose trial evaluating the safety and efficacy of a SGT-001, single IV infusion of AAV9 vector containing a microdystrophin construct in DMD patients (4-17 years old) for 12 months. At the conclusion of the trial, treatment and control groups will be followed for 5 years. The primary efficacy endpoint is the change from baseline in microdystrophin protein production in muscle-biopsy material, using western blot testing.⁹⁶ Long-term interim data on biopsy findings from three patients demonstrated clinical evidence of durable microdystrophin protein expression after 2 years of treatment.^96,97

The CIFFREO trial will assess the safety and efficacy of the PF-06939926 microdystrophin gene therapy, an investigational AAV9 containing microdystrophin, in approximately 99 ambulatory DMD patients (4-7 years of age). The study is a randomized, double-blind, placebo-controlled, multicenter phase 3 trial. The primary efficacy end-point is the change from baseline in the North Star Ambulatory Assessment (NSAA), which measures gross motor function. This will be assessed at 52 weeks; all study participants will be followed for a total of 5 years post-treatment.^98,99,100 Due to unexpected patient death (in a non-ambulatory cohort) in the phase 1b (in a non-ambulatory cohort) in the phase 1b (ClinicalTrial.gov Identifier: (NCT03362502) trial, microdystrophin gene therapy was immediately placed on clinical hold.^101,102 The amended study protocol required that all participants undergo one week of in-hospital observation after receiving treatment.¹⁰²

The EMBARK study is a global, randomized, double-blind, placebo-controlled, phase 3 trial that is evaluating the safety and efficacy of SRP-9001, which is a rAAVrh74.MHCK7.microdystrophin gene therapy. The AAV vector (rAAVrh74) contains the microdystrophin construct, driven by the skeletal and cardiac muscle–specific promoter, MHCK7.98,99 In the EMBARK study, approximately 120 participants with DMD (4-7 years of age) will be enrolled. The primary efficacy endpoint includes the change from baseline to week 52 in the NSAA total score.⁹⁹ Based on SRP-9001, data demonstrating consistent statistically significant functional improvements in NSAA total scores and timed function tests (after one-year post- treatment) in DMD patients from previous studies and an integrated analysis from multiple studies (ClinicalTrial.gov Identifier: NCT03375164, NCT03769116, and NCT04626674), the ongoing EMBARK has great promise.^103,104
 

Challenges ahead, but advancements realized

Novel gene-based therapies show significant potential for transforming the treatment of NMDs. The complex pathologies of NMDs have been a huge challenge to disease management in an area once considered unremediable by gene-based therapy. However, advancements in precision medicine – specifically, gene-delivery systems (for example, AAV9 and AAVrh74 vectors) combined with gene modification strategies (ASOs and AAV-mediated silencing) – have the potential to, first, revolutionize standards of care for sporadic and inherited NMDs and, second, significantly reduce disease burden.⁶

What will be determined to be the “best” therapeutic approach will, likely, vary from NMD to NMD; further investigation is required to determine which agents offer optimal clinical efficacy and safety profiles.⁴³ Furthermore, the key to therapeutic success will continue to be early detection and diagnosis – first, by better understanding disease pathology and drug targets and, second, by validation of reliable biomarkers that are predictive of therapeutic benefit.^4,5

To sum up, development challenges remain, but therapeutic approaches to ALS, SMA, and DMD that utilize novel gene-delivery and gene-manipulation tools show great promise.



Ms. Yewhalashet is a student in the masters of business and science program, with a concentration in healthcare economics, at Keck Graduate Institute Henry E. Riggs School of Applied Life Sciences, Claremont, Calif. Dr. Davis is professor of practice in clinical and regulatory affairs, Keck Graduate Institute Henry E. Riggs School of Applied Life Sciences.
 

References

1. Aitken M et al. Understanding neuromuscular disease care. IQVIA [Internet]. Oct 30, 2018. Accessed Mar 1, 2022. https://www.iqvia.com/insights/the-iqvia-institute/reports/understanding-neuromuscular-disease-care.

2. National Institute of Neurological Disorders and Stroke. Neurological diagnostic tests and procedures fact sheet. Updated Nov 15, 2021. Ac-cessed Mar 1, 2022. http://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Neurological-Diagnostic-Tests-and-Procedures-Fact.

3. Deenen JCW et al. The epidemiology of neuromuscular disorders: A comprehensive overview of the literature. J Neuromuscul Dis. 2015;2(1):73-85.

4. Cavazzoni P. The path forward: Advancing treatments and cures for neurodegenerative diseases. U.S. Food and Drug Administration. Jul 29, 2021. Accessed Mar 1, 2022. http://www.fda.gov/news-events/congressional-testimony/path-forward-advancing-treatments-and-cures-neurodegenerative-diseases-07292021.

5. Martier R, Konstantinova P. Gene therapy for neurodegenerative diseases: Slowing down the ticking clock. Front Neurosci. 2020 Sep 18;14:580179. doi: 10.3389/fnins.2020.580179.

6. Sun J, Roy S. Gene-based therapies for neurodegenerative diseases. Nat Neurosci. 2021 Mar;24(3):297-311. doi:10.1038/s41593-020-00778-1.

7. Amado DA, Davidson BL. Gene therapy for ALS: A review. Mol Ther. 2021 Dec 1;29(12):3345-58. doi:10.1016/j.ymthe.2021.04.008.

8. Yun Y, Ha Y. CRISPR/Cas9-mediated gene correction to understand ALS. Int J Mol Sci. 2020;21(11):3801. doi:10.3390/ijms21113801.

9. National Institute of Neurological Disorders and Stroke. Amyotrophic lateral sclerosis (ALS) fact sheet. Updated Nov 15, 2021. Accessed Mar 1, 2022. http://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Amyotrophic-Lateral-Sclerosis-ALS-Fact-Sheet.

10. Cappella M et al. Gene therapy for ALS – A perspective. Int J Mol Sci. 2019;20(18):4388. doi:10.3390/ijms20184388.

11. Abramzon YA, Fratta P, Traynor BJ, Chia R. The Overlapping Genetics of Amyotrophic Lateral Sclerosis and Frontotemporal Dementia. Front Neurosci. 2020;14. Accessed August 18, 2022. https://www.frontiersin.org/articles/10.3389/fnins.2020.00042

12. Giannini M, Bayona-Feliu A, Sproviero D, Barroso SI, Cereda C, Aguilera A. TDP-43 mutations link Amyotrophic Lateral Sclerosis with R-loop homeostasis and R loop-mediated DNA damage. PLOS Genet. 2020;16(12):e1009260. doi:10.1371/journal.pgen.1009260

13. FDA-approved drugs for treating ALS. The ALS Association [Internet]. Accessed Mar 1, 2022. http://www.als.org/navigating-als/living-with-als/fda-approved-drugs.

14. Jensen TL et al. Current and future prospects for gene therapy for rare genetic diseases affecting the brain and spinal cord. Front Mol Neurosci. 2021 Oct 6;14:695937. doi:10.3389/fnmol.2021.695937.

15. ALS Gene Targeted Therapies. The ALS Association. Accessed August 22, 2022. https://www.als.org/understanding-als/who-gets-als/genetic-testing/als-gene-targeted-therapies

16. Tofersen for ALS clears phase 1/2 trial, now in phase 3. Advances in Motion. Massachusetts General Hospital [Internet]. Sep 30, 2020. Accessed Mar 1, 2022. https://advances.massgeneral.org/neuro/journal.aspx?id=1699.17. Biogen. A study to evaluate the efficacy, safety, tol-erability, pharmacokinetics, and pharmacodynamics of BIIB067 administered to adult subjects with amyotrophic lateral sclerosis and confirmed superoxide dismutase 1 mutation. ClinicalTrials.gov Identifier: NCT02623699. Updated Jul 25, 2021. Accessed Feb 17, 2022. https://clinicaltrials.gov/ct2/show/NCT02623699.

18. Biogen. Biogen announces topline results from the tofersen phase 3 study and its open-label Extension in SOD1-ALS. Press release. Oct 17, 2021. Accessed Mar 1, 2022. https://investors.biogen.com/news-releases/news-release-details/biogen-announces-topline-results-tofersen-phase-3-study-and-its.

19. Biogen. An extension study to assess the long-term safety, tolerability, pharmacokinetics, and effect on disease progression of BIIB067 ad-ministered to previously treated adults with amyotrophic lateral sclerosis caused by superoxide dismutase 1 mutation. ClinicalTrials.gov Identi-fier: NCT03070119. Updated Sep 10, 2021. Accessed Feb 17, 2022. https://clinicaltrials.gov/ct2/show/NCT03070119.

20. MS MW. #AANAM – ATLAS Trial to Assess Tofersen in Presymptomatic SOD1 ALS. Accessed February 19, 2022. https://alsnewstoday.com/news-posts/2021/04/23/aanam-atlas-clinical-trial- tofersen-presymptomatic-sod1-als-patients/

21.Biogen. A phase 3 randomized, placebo-controlled trial with a longitudinal natural history run-in and open-label extension to evaluate BIIB067 initiated in clinically presymptomatic adults with a confirmed superoxide dismutase 1 mutation. ClinicalTrials.gov Identifier: NCT04856982. Updated Feb 18, 2022. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT04856982.

22. Latozinemab | ALZFORUM. Accessed August 19, 2022. https://www.alzforum.org/therapeutics/latozinemab

23. Alector Presents AL001 (latozinemab) Data from the FTD-C9orf72 Cohort of the INFRONT-2 Phase 2 Clinical Trial | Alector. Accessed August 18, 2022. https://investors.alector.com/news- releas-es/news-release-details/alector-presents-al001-latozinemab-data-ftd-c9orf72-cohort/

24. Alector Announces First Participant Dosed in Phase 2 Study Evaluating AL001 in Amyotrophic Lateral Sclerosis (ALS) | Alector. Accessed August 18, 2022. https://investors.alector.com/news- releases/news-release-details/lector-announces-first-participant-dosed-phase-2-study-0/ 25. A Phase 2 Study to Evaluate AL001 in C9orf72-Associated ALS - Full Text View - ClinicalTrials.gov. Accessed August 19, 2022. https://clinicaltrials.gov/ct2/show/NCT05053035

26.TPN-101 | ALZFORUM. Accessed August 19, 2022. https://www.alzforum.org/therapeutics/tpn- 101

27. Transposon Therapeutics, Inc. A Phase 2a Study of TPN-101 in Patients With Amyotrophic Lateral Sclerosis (ALS) and/or Frontotemporal Dementia (FTD) Associated With Hexanucleotide Repeat Expansion in the C9orf72 Gene (C9ORF72 ALS/FTD). clinicaltrials.gov; 2022. Ac-cessed August 17, 2022. https://clinicaltrials.gov/ct2/show/NCT04993755

28. Kerk SY, Bai Y, Smith J, et al. Homozygous ALS-linked FUS P525L mutations cell- autonomously perturb transcriptome profile and chem-oreceptor signaling in human iPSC microglia. Stem Cell Rep. 2022;17(3):678-692. doi:10.1016/j.stemcr.2022.01.004

29. ION363 | ALZFORUM. Accessed August 19, 2022. https://www.alzforum.org/therapeutics/ion363 30. Ionis Pharmaceuticals, Inc. A Phase 1-3 Study to Evaluate the Efficacy, Safety, Pharmacokinetics and Pharmacodynamics of Intrathecally Administered ION363 in Amyo-trophic Lateral Sclerosis Patients With Fused in Sarcoma Mutations (FUS-ALS). clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT04768972

31. PhD LF. Engensis (VM202) - ALS News Today. Accessed August 19, 2022. https://alsnewstoday.com/vm202/

32. Helixmith Co., Ltd. A 6-Month Extension Study Following Protocol VMALS-002-2 (A Phase 2a, Double-Blind, Randomized, Place-bo-Controlled, Multicenter Study to Assess the Safety of Engensis in Participants With Amyotrophic Lateral Sclerosis). clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT05176093 33. Safety of Engensis in Participants With Amyotrophic Lateral Sclerosis - Full Text View - ClinicalTrials.gov. Accessed August 19, 2022. https://clinicaltrials.gov/ct2/show/NCT04632225

34. Biogen. A phase 1, safety, tolerability, and distribution study of a microdose of radiolabeled BIIB067 co-administered with BIIB067 to healthy adults. ClinicalTrials.gov Identifier: NCT03764488. Updated Jul 19, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT03764488.

35. Ionis Pharmaceuticals Inc. A phase 1, double-blind, placebo-controlled, dose-escalation study of the safety, tolerability, and pharmacokinet-ics of ISIS 333611 administered intrathecally to patients with familial amyotrophic lateral sclerosis due to superoxide dismutase 1 gene muta-tions. ClinicalTrials.gov Identifier: NCT01041222. Updated Apr 13, 2012. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT01041222.

36. Messina S, Sframeli M. New treatments in spinal muscular atrophy: Positive results and new challenges. J Clin Med. 2020;9(7):2222. doi:10.3390/jcm9072222.

37. Scoto M et al. Genetic therapies for inherited neuromuscular disorders. Lancet Child Adolesc Health. 2018 Aug;2(8):600-9. doi:10.1016/S2352-4642(18)30140-8.

38. Abreu NJ, Waldrop MA. Overview of gene therapy in spinal muscular atrophy and Duchenne muscular dystrophy. Pediatr Pulmonol. 2021 Apr;56(4):710-20. doi:10.1002/ppul.25055.

39. Brandsema J, Cappa R. Genetically targeted therapies for inherited neuromuscular disorders. Practical Neurology [Internet]. Jul/Aug 2021:69-73. Accessed Mar 1, 2022. https://practicalneurology.com/articles/2021-july-aug/genetically-targeted-therapies-for-inherited-neuromuscular-disorders/pdf.

40. Ojala KS et al. In search of a cure: The development of therapeutics to alter the progression of spinal muscular atrophy. Brain Sci. 2021;11(2):194. doi:10.3390/brainsci11020194.

41. McCall S. Cure SMA Releases Updated Drug Pipeline. Cure SMA. Published December 13, 2021. Accessed August 21, 2022. https://www.curesma.org/cure-sma-releases-updated-drug-pipeline- 2021/ 42. FDA approves first drug for spinal muscular atrophy. U.S. Food and Drug Administration. News release. Dec 23, 2016. Accessed Mar 1, 2022. http://www.fda.gov/news-events/press-announcements/fda-approves-first-drug-spinal-muscular-atrophy.43. Kirschner J. Postnatal gene therapy for neuromuscular diseases – Opportunities and limitations. J Perinat Med. 2021 Sep;49(8):1011-5. doi:10.1515/jpm-2021-0435.

43. Terryn J, Verfaillie CM, Van Damme P. Tweaking Progranulin Expression: Therapeutic Avenues and Opportunities. Front Mol Neurosci. 2021;14. Accessed September 4, 2022. https://www.frontiersin.org/articles/10.3389/fnmol.2021.71303144.

44. Biogen. A phase 3, randomized, double-blind, sham-procedure controlled study to assess the clinical efficacy and safety of ISIS 396443 administered intrathecally in patients with later-onset spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT02292537. Updated Feb 17, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/study/NCT02292537.

45. Why Spinraza/later-onset studies. SPINRAZA® (nusinersen) [Internet]. Accessed Mar 1, 2022. www.spinraza.com/en_us/home/why-spinraza/later-onset-studies.html#scroll-tabs.

46. Biogen. A Phase 3, Randomized, Double-Blind, Sham-Procedure Controlled Study to Assess the Clinical Efficacy and Safety of ISIS 396443 Administered Intrathecally in Patients With Infantile- Onset Spinal Muscular Atrophy. clinicaltrials.gov; 2021. Accessed February 10, 2022. https://clinicaltrials.gov/ct2/show/results/NCT02193074

47. Early-onset SMA (Type 1) | SPINRAZA® (nusinersen). Accessed Mar 1, 2022. https://www.spinraza-hcp.com/en_us/home/why-spinraza/about-spinraza.html.

48. Finkel RS et al; ENDEAR Study Group. Nusinersen versus sham control in infantile-onset spinal muscular atrophy. N Engl J Med. 2017;377(18):1723-32. doi: 10.1056/NEJMoa1702752.

49. Biogen. An open-label study to assess the efficacy, safety, tolerability, and pharmacokinetics of multiple doses of ISIS 396443 delivered intrathecally to subjects with genetically diagnosed and presymptomatic spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT02386553. Updated Nov 18, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT02386553.

50. De Vivo DC et al; NURTURE Study Group. Nusinersen initiated in infants during the presymptomatic stage of spinal muscular atrophy: In-terim efficacy and safety results from the phase 2 NURTURE study. Neuromuscul Disord. 2019 Nov;29(11):842-56. doi:10.1016/j.nmd.2019.09.007.

51. Why Spinraza/presymptomatic study. SPINRAZA® (nusinersen) [Internet]. Accessed Feb 22, 2022. www.spinraza.com/en_us/home/why-spinraza/presymptomatic-study.html#scroll-tabs.

52. FDA approves oral treatment for spinal muscular atrophy. U.S. Food and Drug Administration. News release. Aug 7, 2020. Accessed Mar 1, 2022. http://www.fda.gov/news-events/press-announcements/fda-approves-oral-treatment-spinal-muscular-atrophy.

53. Hoffmann-La Roche. A two-part seamless, open-label, multicenter study to investigate the safety, tolerability, pharmacokinetics, pharmaco-dynamics and efficacy of risdiplam (RO7034067) in infants with type 1 spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT02913482. Updated Jan 21, 2022. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT02913482.

54. Hoffmann-La Roche. A two-part seamless, multi-center randomized, placebo-controlled, double-blind study to investigate the safety, tolera-bility, pharmacokinetics, pharmacodynamics and efficacy of risdiplam (RO7034067) in type 2 and 3 spinal muscular atrophy patients. Clinical-Trials.gov Identifier: NCT02908685. Updated Dec 28, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT02908685.

55. Genentech. Genentech’s risdiplam shows significant improvement in survival and motor milestones in infants with type 1 spinal muscular atrophy (SMA). Press release. Apr 27, 2020. Accessed Mar 1, 2022. http://www.gene.com/media/press-releases/14847/2020-04-27/genentechs-risdiplam-shows-significant-i

56. Hoffmann-La Roche. An open-label study to investigate the safety, tolerability, and pharmacokinetics/pharmacodynamics of risdiplam (RO7034067) in adult and pediatric patients with spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT03032172. Updated Jan 27, 2022. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT03032172.

57. Hoffmann-La Roche. An open-label study of risdiplam in infants with genetically diagnosed and presymptomatic spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT03779334. Updated Jan 27, 2022. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT03779334.

58. McCall S. Update on Genentech/Roche Initiation of MANATEE Clinical Study. Cure SMA. Published October 20, 2021. Accessed August 20, 2022. https://www.curesma.org/update-on- genentech-roche-initiation-of-manatee-clinical-study/

59. Abati E, Manini A, Comi GP, Corti S. Inhibition of myostatin and related signaling pathways for the treatment of muscle atrophy in motor neuron diseases. Cell Mol Life Sci. 2022;79(7):374. doi:10.1007/s00018-022-04408-w

60. FDA approves innovative gene therapy to treat pediatric patients with spinal muscular atrophy, a rare disease and leading genetic cause of infant mortality. U.S. Food and Drug Administration. News release. May 24, 2019. Accessed Mar 1, 2022. http://www.fda.gov/news-events/press-announcements/fda-approves-innovative-gene-therapy-treat-pediatric-patients-spinal-muscular-atrophy-rare-disease.

61. Novartis Gene Therapies. Phase I gene transfer clinical trial for spinal muscular atrophy type 1 delivering AVXS-101. ClinicalTrials.gov Identifier: NCT02122952. Updated Jun 14, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT02122952.

62. Novartis Gene Therapies. Phase 3, open-label, single-arm, single-dose gene replacement therapy clinical trial for patients with spinal mus-cular atrophy type 1 with one or two SMN2 copies delivering AVXS-101 by intravenous infusion. ClinicalTrials.gov Identifier: NCT03306277. Updated Jun 14, 2021. Accessed Feb 21, 2022. https://clinicaltrials.gov/ct2/show/NCT03306277.

63. Mendell JR et al. Single-dose gene-replacement therapy for spinal muscular atrophy. N Engl J Med. 2017;377(18):1713-22. doi:10.1056/NEJMoa1706198.

64. Symptomatic study results. ZOLGENSMA [Internet]. Updated Nov 2021. Accessed Mar 1, 2022. Error! Hyperlink reference not valid..

65. Novartis Gene Therapies. A global study of a single, one-time dose of AVXS-101 delivered to infants with genetically diagnosed and pre-symptomatic spinal muscular atrophy with multiple copies of SMN2. ClinicalTrials.gov Identifier: NCT03505099. Updated Jan 1, 2022. Ac-cessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT03505099.

66. Chiu W et al. Current genetics and potential gene-targeting therapeutics for neuromuscular diseases. Int J Mol Sci. 2020 Dec;21(24):9589. doi:10.3390/ijms21249589.

67. Novartis Gene Therapies. A long-term follow-up study of patients in the clinical trials for spinal muscular atrophy receiving AVXS-101. Clini-calTrials.gov Identifier: NCT04042025. Updated Jun 9, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT04042025.

68. Novartis Gene Therapies. Phase 3, open-label, single-arm, single-dose gene replacement therapy clinical trial for patients with spinal mus-cular atrophy type 1 with one or two SMN2 copies delivering AVXS-101 by intravenous infusion. ClinicalTrials.gov Identifier: NCT0383718. Up-dated Jan 11, 2022. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT03837184.

69. Biogen. An open-label, dose escalation study to assess the safety, tolerability and dose-range finding of multiple doses of ISIS 396443 de-livered intrathecally to patients with spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT01703988. Updated Apr 13, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT01703988.

70. Biogen. A study to assess the efficacy, safety, tolerability, and pharmacokinetics of multiple doses of ISIS 396443 delivered intrathecally to patients with infantile-onset spinal muscular atrophy. ClinicalTrials.gov Identifier: NCT01839656. Updated Feb 17, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT01839656.

71. Biogen. An open-label extension study for patients with spinal muscular atrophy who previously participated in investigational studies of ISIS 396443. ClinicalTrials.gov Identifier: NCT02594124. Updated Nov 15, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT02594124.

72. Biogen. Escalating dose and randomized, controlled study of nusinersen (BIIB058) in participants with spinal muscular atrophy. ClinicalTri-als.gov Identifier: NCT04089566. Updated Feb 24, 2022. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT04089566.

73. National Center for Advancing Translational Sciences. Duchenne muscular dystrophy. Genetic and Rare Diseases Information Center. Up-dated Nov 2, 2020. Accessed Mar 1, 2022. https://rarediseases.info.nih.gov/diseases/6291/duchenne-muscular-dystrophy.

74. Matsuo M. Antisense oligonucleotide-mediated exon-skipping therapies: Precision medicine spreading from Duchenne muscular dystrophy. JMA J. 2021 Jul 15;4(3):232-40. doi:10.31662/jmaj.2021-0019.

75. FDA approves drug to treat Duchenne muscular dystrophy. U.S. Food and Drug Administration. News release. Feb 9, 2017. Accessed Mar 1, 2022. http://www.fda.gov/news-events/press-announcements/fda-approves-drug-treat-duchenne-muscular-dystrophy.74.

76. Duan D. Dystrophin gene replacement and gene repair therapy for Duchenne muscular dystrophy in 2016: An interview. Hum Gene Ther Clin Dev. 2016 Mar;27(1):9-18. doi:10.1089/humc.2016.001.

77. EXONDYS 51®. Parent Project Muscular Dystrophy. Accessed August 21, 2022. https://www.parentprojectmd.org/drug-development-pipeline/exondys-51/

78. Sarepta Therapeutics, Inc. A Randomized, Double-Blind, Placebo-Controlled, Multiple Dose Efficacy, Safety, Tolerability and Pharmacoki-netics Study of AVI-4658(Eteplirsen),in the Treatment of Ambulant Subjects With Duchenne Muscular Dystrophy. clinicaltrials.gov; 2020. Ac-cessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT01396239

79. Sarepta Therapeutics, Inc. Clinical Study to Assess the Safety Fo AVI-4658 in Subjects With Duchenne Muscular Dystrophy Due to a Frame-Shift Mutation Amenable to Correction by Skipping Exon 51. clinicaltrials.gov; 2015. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/study/NCT00844597

80. Sarepta Therapeutics, Inc. A 2-part, randomized, double-blind, placebo-controlled, dose-titration, safety, tolerability, and pharmacokinetics study (Part 1) followed by an open-label efficacy and safety evaluation (Part 2) of SRP-4053 in patients with Duchenne muscular dystrophy amenable to exon 53 skipping. ClinicalTrials.gov Identifier: NCT02310906. Updated Oct 19, 2020. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/results/NCT02310906.

81. Commissioner O of the. FDA grants accelerated approval to first drug for Duchenne muscular dystrophy. FDA. Published March 24, 2020. Accessed August 21, 2022. hDuchenne Muscular Dystrophy Amenable to Exon 51-Skipping Treatment. clinicaltrials.gov; 2022. Accessed Au-gust 18, 2022. https://clinicaltrials.gov/ct2/show/NCT04004065

109. National Center of Neurology and Psychiatry, Japan. Exploratory study of NS-065/NCNP-01 in Duchenne muscular dystrophy. ClinicalTri-als.gov Identifier: NCT02081625; Updated Feb 26, 2020. Accessed Mar 2, 2022. https://clinicaltrialsttps://www.fda.gov/news-events/press-announcements/fda-grants-accelerated-approval-first-drug-duchenne-muscular- dys-trophy

82. Duchenne Drug Development Pipeline. Parent Project Muscular Dystrophy. Accessed August 21, 2022. https://www.parentprojectmd.org/duchenne-drug-development-pipeline/

83. Sarepta Therapeutics Provides Update on SRP-5051 for the Treatment of Duchenne Muscular Dystrophy | Sarepta Therapeutics, Inc. Ac-cessed August 22, 2022. https://investorrelations.sarepta.com/news-releases/news-release-details/sarepta-therapeutics- pro-vides-update-srp-5051-treatment-duchenne

84. Sarepta Therapeutics, Inc. An Open-Label Extension Study for Patients With Duchenne Muscular Dystrophy Who Participated in Studies of SRP-5051. clinicaltrials.gov; 2021. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT03675126

85. VYONDYS 53. Prescribing information. Sarepta Therapeutics Inc.; 2019. Accessed Mar 2, 2022. http://www.accessdata.fda.gov/drugsatfda_docs/label/2019/211970s000lbl.pdf.

86. NS Pharma Inc. Long-term use of viltolarsen in boys with Duchenne muscular dystrophy in clinical practice (VILT-502). ClinicalTrials.gov Identifier: NCT04687020. Updated Nov 22, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT04687020.

87. VILTEPSO. Prescribing information. NS Pharma; 2020. Accessed Mar 2, 2022. http://www.accessdata.fda.gov/drugsatfda_docs/label/2020/212154s000lbl.pdf.

88. FDA approves targeted treatment for rare Duchenne muscular dystrophy mutation. U.S. Food and Drug Administration. News release. Feb 25, 2021. Accessed Mar 1, 2022. http://www.fda.gov/news-events/press-announcements/fda-approves-targeted-treatment-rare-duchenne-muscular-dystrophy-mutation-0.

89. Sarepta Therapeutics Inc. A double-blind, placebo-controlled, multi-center study with an open-label extension to evaluate the efficacy and safety of SRP-4045 and SRP-4053 in patients with Duchenne muscular dystrophy. Clinicaltrials.gov Identifier: NCT02500381. Updated Aug 19, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT02500381.

90. AMONDYS 45. Prescribing information. Sarepta Therapeutics Inc.; 2021. Accessed Feb 22, 2022. http://www.accessdata.fda.gov/drugsatfda_docs/label/2021/213026lbl.pdf.

91. Finkel RS et al. Phase 2a study of ataluren-mediated dystrophin production in patients with nonsense mutation Duchenne muscular dys-trophy. PLoS ONE. 2013;8(12):e81302. doi:10.1371/journal.pone.0081302.

92. PTC Therapeutics. A phase 2 study of PTC124 as an oral treatment for nonsense-mutation-mediated Duchenne muscular dystrophy. Clini-calTrials.gov Identifier: NCT00264888. Updated Jan 14, 2009. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT00264888.

93. PTC Therapeutics. A phase 2B efficacy and safety study of PTC124 in subjects with nonsense-mutation-mediated Duchenne and Becker muscular dystrophy. ClinicalTrials.gov Identifier: NCT00592553. Updated Apr 7, 2020. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT00592553.

94. PTC Therapeutics. A phase 3 efficacy and safety study of ataluren in patients with nonsense mutation dystrophinopathy. ClinicalTrials.gov Identifier: NCT01826487. Updated Aug 4, 2020. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT01826487.

95. Bushby K et al; PTC124-GD-007-DMD Study Group. Ataluren treatment of patients with nonsense mutation dystrophinopathy. Muscle Nerve. 2014 Oct;50(4):477-87. doi:10.1002/mus.24332.

96. Solid Biosciences LLC. A randomized, controlled, open-label, single-ascending dose, phase I/II study to investigate the safety and tolerabil-ity, and efficacy of intravenous SGT-001 in male adolescents and children with Duchenne muscular dystrophy. ClinicalTrials.gov Identifier: NCT03368742. Updated Aug 24, 2021. Accessed Mar 1, 2022. https://clinicaltrials.gov/ct2/show/NCT03368742.

97. Solid Biosciences reports 1.5-year data from patients in the ongoing IGNITE DMD phase I/II clinical trial of SGT-001. Press release. Solid Biosciences. Sep 27, 2021. Accessed Mar 2, 2022. http://www.solidbio.com/about/media/press-releases/solid-biosciences-reports-1-5-year-data-from-patients-in-the-ongoing-ignite-dmd-phase-i-ii-clinical-trial-of-sgt-001.

98. Potter RA et al. Dose-escalation study of systemically delivered rAAVrh74.MHCK7.microdystrophin in the mdx mouse model of Duchenne muscular dystrophy. Hum Gene Ther. 2021 Apr;32(7-8):375-89. doi:10.1089/hum.2019.255.

99. Sarepta Therapeutics, Inc. A Phase 3 Multinational, Randomized, Double-Blind, Placebo- Controlled Systemic Gene Delivery Study to Evaluate the Safety and Efficacy of SRP-9001 in Patients With Duchenne Muscular Dystrophy (EMBARK). clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT05096221

100. Pfizer. A PHASE 3, MULTICENTER, RANDOMIZED, DOUBLE-BLIND, PLACEBO CONTROLLED STUDY TO EVALUATE THE SAFETY AND EFFICACY OF PF 06939926 FOR THE TREATMENT OF DUCHENNE MUSCULAR DYSTROPHY. clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT04281485

101. Pfizer. A phase 1B multicenter open-label, single ascending dose study to evaluate the safety and tolerability of PF-06939926 in ambula-tory and non-ambulatory subjects with Duchenne muscular dystrophy. ClinicalTrials.gov Identifier: NCT03362502. Updated Mar 2, 2022. Ac-cessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT03362502.

102. MS MW. Phase 3 CIFFREO DMD Gene Therapy Trial Slated to Begin in June in US. Accessed August 21, 2022. https://musculardystrophynews.com/news/phase-3-trial-of-pfizers-gene-therapy- expected-to-open-in-us-in-june/

103. SRP-9001. Parent Project Muscular Dystrophy. Accessed August 22, 2022. https://www.parentprojectmd.org/drug-development-pipeline/srp-9001-micro-dystrophin-gene- transfer/

104. Sarepta Therapeutics’ Investigational Gene Therapy SRP-9001 for Duchenne Muscular Dystrophy Demonstrates Significant Functional Improvements Across Multiple Studies | Sarepta Therapeutics, Inc. Accessed August 22, 2022. https://investorrelations.sarepta.com/news-releases/news-release- details/sarepta-therapeutics-investigational-gene-therapy-srp-9001

105. Sarepta Therapeutics, Inc. An Open-Label Safety, Tolerability, and Efficacy Study of Eteplirsen in Patients With Duchenne Muscular Dys-trophy Who Have Completed Study 4658-102.clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT03985878

106. Sarepta Therapeutics, Inc. An Open-Label Safety, Tolerability, and Pharmacokinetics Study of Eteplirsen in Young Patients With Duchenne Mus-cular Dystrophy Amenable to Exon 51 Skipping. clinicaltrials.gov; 2021. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT03218995

107.Sarepta Therapeutics, Inc. A Randomized, Double-Blind, Dose Finding and Comparison Study of the Safety and Efficacy of a High Dose of Eteplirsen, Preceded by an Open-Label Dose Escalation, in Patients With Duchenne Muscular Dystrophy With Deletion Mutations Amenable to Exon 51 Skipping. clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT03992430

108. Sarepta Therapeutics, Inc. A Phase 2, Two-Part, Multiple-Ascending-Dose Study of SRP-5051 for Dose Determination, Then Dose Ex-pansion, in Patients With .gov/ct2/show/NCT02081625.

110. NS Pharma Inc. A phase II, dose finding study to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics of NS-065/NCNP-01 in boys with Duchenne muscular dystrophy (DMD). ClinicalTrials.gov Identifier: NCT02740972. Updated Dec 7, 2021. Ac-cessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT02740972.

111. NS Pharma Inc. A phase II, open-label, extension study to assess the safety and efficacy of NS-065/NCNP-01 in boys with Duchenne muscular dystrophy (DMD). ClinicalTrials.gov Identifier: NCT03167255. Updated Nov 24, 2021. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT03167255.

112. NS Pharma Inc. A phase 2 open label study to assess the safety, tolerability, and efficacy of viltolarsen in ambulant and non-ambulant boys with Duchenne muscular dystrophy (DMD) compared with natural history controls. ClinicalTrials.gov Identifier: NCT04956289. Updated Feb 1, 2022. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT04956289.

113. NS Pharma Inc. A phase 3 randomized, double-blind, placebo-controlled, multi-center study to assess the efficacy and safety of viltolarsen in ambulant boys with Duchenne muscular dystrophy (DMD). ClinicalTrials.gov Identifier: NCT04060199. Updated Nov 16, 2021. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT04060199.

114. NS Pharma Inc. A phase 3, multi-center, open-label extension study to assess the safety and efficacy of viltolarsen in ambulant boys with Duchenne muscular dystrophy (DMD). ClinicalTrials.gov Identifier: NCT04768062. Updated Nov 16, 2021. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT04768062.

115. Sarepta Therapeutics Inc. A randomized, double-blind, placebo-controlled, dose-titration, safety, tolerability, and pharmacokinetics study followed by an open-label safety and efficacy evaluation of SRP-4045 in advanced-stage patients with Duchenne muscular dystrophy amena-ble to exon 45 skipping. ClinicalTrials.gov Identifier: NCT02530905. Updated May 17, 2021. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT02530905.

116. Sarepta Therapeutics Inc. Long-term, open-label extension study for patients with Duchenne muscular dystrophy enrolled in clinical trials evaluating casimersen or golodirsen. ClinicalTrials.gov Identifier: NCT03532542. Updated Dec 20, 2021. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT03532542.

117. PTC Therapeutics. A phase 2 study of the safety, pharmacokinetics, and pharmacodynamics of ataluren (PTC124®) in patients aged ≥2 to <5 years old with nonsense mutation dystrophinopathy. ClinicalTrials.gov Identifier: NCT02819557. Updated Aug 28, 2020. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT02819557.

118. PTC Therapeutics. Phase 2, non-interventional, clinical study to assess dystrophin levels in subjects with nonsense mutation Duchenne muscular dystrophy who have been treated with ataluren for ≥ 9 months. ClinicalTrials.gov Identifier: NCT03796637. Updated Apr 10, 2020. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT03796637.

119. PTC Therapeutics. An Open-Label Study Evaluating the Safety and Pharmacokinetics of Ataluren in Children From ≥6 Months to <2 Years of Age With Nonsense Mutation Duchenne Muscular Dystrophy. clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT04336826 120. PTC Therapeutics. An open-label study for previously treated ataluren (PTC124®) pa-tients with nonsense mutation dystrophinopathy. ClinicalTrials.gov Identifier: NCT01557400. Updated Nov 25, 2020. Accessed Feb 21, 2022. https://clinicaltrials.gov/ct2/show/NCT01557400.

121. PTC Therapeutics. An open-label, safety study for ataluren (PTC124) patients with nonsense mutation dystrophinopathy. ClinicalTrials.gov Identifier: NCT01247207. Updated Feb 16, 2022. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT01247207.

122. PTC Therapeutics. A phase 3, randomized, double-blind, placebo-controlled efficacy and safety study of ataluren in patients with non-sense mutation Duchenne muscular dystrophy and open-label extension. ClinicalTrials.gov Identifier: NCT03179631. Updated Feb 8, 2022. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT03179631.

123. Sarepta Therapeutics, Inc. An Open-Label, Systemic Gene Delivery Study Using Commercial Process Material to Evaluate the Safety of and Expression From SRP-9001 in Subjects With Duchenne Muscular Dystrophy (ENDEAVOR). clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT04626674

124. Sarepta Therapeutics, Inc. Systemic Gene Delivery Phase I/IIa Clinical Trial for Duchenne Muscular Dystrophy Using RAA-Vrh74.MHCK7.Micro-Dystrophin (MicroDys-IV-001). clinicaltrials.gov; 2022. Accessed August 18, 2022. https://clinicaltrials.gov/ct2/show/NCT03375164

125. Sarepta Therapeutics Inc. A multicenter, randomized, double-blind, placebo-controlled trial for Duchenne muscular dystrophy using SRP-9001. ClinicalTrials.gov Identifier: NCT03769116. Updated Dec 2021. Accessed Mar 2, 2022. https://clinicaltrials.gov/ct2/show/NCT03769116.

126. Hoffmann-La Roche. A Two-Part, Seamless, Multi-Center, Randomized, Placebo-Controlled, Double-Blind Study to Investigate the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics and Efficacy of RO7204239 in Combination With Risdiplam (RO7034067) in Ambulant Pa-tients With Spinal Muscular Atrophy. clinicaltrials.gov; 2022. Accessed September 1, 2022. https://clinicaltrials.gov/ct2/show/NCT05115110