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Has prompt diagnosis of amyotrophic lateral sclerosis become urgent?
Amyotrophic lateral sclerosis (ALS) falls easily into the Food and Drug Administration definition of “rare disease.” With an estimated prevalence in the United States of fewer than 20,000 cases,1 ALS sits comfortably below the cutoff of 200,000 cases that serves to define a disease as “rare.”
After a recent steep climb, there are something on the order of 50 therapies, across more than 10 drug classes, in clinical trials for the treatment of ALS.2 This bounty represents exciting progress toward the development of targeted therapies for a characteristically fatal disease.
That headway is coupled with a sobering limitation, however: Relatively few ALS patients are being enrolled.
The knotty problem with therapeutic trials for ALS
“Trials are generally designed for patients with adequate functional reserve and predicted survival, to ensure that a signal of benefit can be seen,” said Nicholas John Maragakis, MD, director of the ALS Clinical Trials Unit at Johns Hopkins University, Baltimore. “Many of my patients are too severely affected at presentation.”
Dr. Maragakis hasn’t calculated the precise percentage of patients he is enrolling in one of the many available trials available at the Johns Hopkins center. He estimates that it is less than 20%, however.
That percentage is comparable to what is reported by Stephen Scelsa, MD, and Daniel J. Macgowan, MD, who share much of the ALS caseload in a dedicated, comprehensive ALS center at Mount Sinai Beth Israel, New York. Both are on the faculty at the Icahn School of Medicine at Mount Sinai.
“The considerable delay in the diagnosis of ALS remains a challenge,” Dr. Scelsa acknowledges. Like Dr. Maragakis, he reports that, by the time patients develop symptoms that make referral to a comprehensive ALS center like Mount Sinai Beth Israel appropriate, many no longer meet eligibility criteria for most experimental treatments.
Some therapeutic targets in clinical trials, such as neuroinflammation, offer potential benefit even in advancing disease, but it is prevention that is usually the goal of experimental ALS therapies. This approach is associated with far more promise than attempting to reverse existing neurologic damage, which might not be possible, according to both Dr. Scelsa and Dr. Macgowan.
“The clinical trials are typically looking for patients with less than 2 years since the onset of symptoms and at least 60% of predicted respiratory function,” Dr. Macgowan said.
Because of these or other similarly restrictive criteria, coupled with common delays before patients arrive at a center where trials are available, “the window for clinical research closes very quickly,” Dr. Macgowan added, and “the band of patients who are eligible is relatively narrow.”
At Hennepin Healthcare in Minneapolis, which, like Johns Hopkins and Mount Sinai, offers an advanced multidisciplinary approach to ALS care in a dedicated clinic, the problem of late referrals is no different. Samuel Maiser, MD, chair of neurology, does attempt to counter this delay by moving quickly.
“I almost always offer a therapeutic trial to a patient with early-stage ALS,” he said. He does so earlier, rather than later, and explains: “I do not want to delay that conversation, because any delay might reduce the chance for getting into a trial.”
The generalist can make a difference in therapeutic success
The proliferation of clinical trials has made early diagnosis of ALS urgent. However, the experts interviewed for this article agreed: Accelerating the time to diagnosis is more dependent on the general neurologist or primary care physician than on the ALS specialist. ALS is a diagnosis of exclusion, but there is now very little delay in reaching a probable diagnosis at a dedicated center.
Yet neurodegenerative complaints in early-stage ALS are often nonspecific and mild; confidence in making a potential diagnosis of ALS is limited among primary care clinicians and general neurologists, who almost always see these patients first. Usually, the problem is not failure to include ALS in the differential diagnosis but hesitation in being candid when there is still doubt.
General neurologists, in particular, Dr. Maragakis said, “are often highly suspicious of a diagnosis of ALS very early on but are concerned about using this term until the clinical signs are more compelling.”
This is understandable. There is reluctance to deliver bad news when confidence in the diagnosis is limited. But the experts agreed: Delayed diagnosis is not in the patient’s interest now that there is at least the potential for entering a trial supported by a scientific rationale for benefit.
“Waiting for 100% certainty – this could actually harm our patients,” Dr. Maiser said. The tendency to avoid delivering bad news, he said, “is human nature, and it is not easy to tell people that ALS is the potential cause, but it’s important for early treatment.”
Some evidence suggests that the incidence of ALS is increasing3 but this is not necessarily evident at the clinical level. “It is not my impression that the incidence of ALS is increasing,” Dr. Macgowan said, “so much as I think we are getting better at making the diagnosis.”
Where we stand: Pathophysiology, diagnosis, treatment
Pathophysiology. ALS is characterized by muscle denervation.4 In the great majority of cases, the disease represents a proteinopathy involving loss of the TDP-43 protein from nuclei. However, pathological heterogeneity means that other pathophysiological mechanisms – mediated by oxidative stress, mitochondrial dysfunction, and neurotoxicity related to excessive stimulation of postsynaptic glutamate receptors – can participate.2,5,6
Approximately 10% of patients have a known gene associated with ALS.7 The rest have what is considered sporadic ALS, although some experts estimate that heritability will eventually be confirmed in 50% or more of cases that have been given the “sporadic” label.8,9 More than 30 genes have been linked to ALS in genomewide association studies. Among patients whose disease carries a known familial link, four genes – SOD1, TARDBP, FUS, and C9orf72 – account for approximately 70% of cases.2
Diagnosis. Genetic testing in patients with suspected or confirmed ALS is the standard of care at most, if not all, comprehensive ALS treatment centers, according to the four experts interviewed by Neurology Reviews 2023 Rare Neurological Disease Special Report for this article. Such testing was routine for years because of its potential for helping researchers to understand subtypes of disease; today, testing has assumed even greater practical value with recent approval of the first ALS gene therapy: Tofersen (Qalsody, Biogen), licensed in 2023, is an antisense oligonucleotide therapy that targets SOD1 mRNA to reduce production of the SOD1 protein, a mediator of disease progression.
“Genetic testing has been useful for telling us something about the disease and its prognosis,” Dr. Maragakis said, “but an approved gene therapy means it can have a direct effect on treatment.”
ALS therapeutics. Other gene therapies are in development. Gene signatures are likely to provide even more opportunities for clinical trials in the future.
Following three loading doses of tofersen at 14-day intervals, the maintenance regimen, administered intrathecally by lumbar puncture, is every 28 days. In the phase 3 trial, tofersen reduced levels of SOD1 protein and neurofilament light chain, a biomarker of axonal injury.10 Tofersen is appropriate only in patients with SOD1-associated ALS; the drug’s favorable clinical impact, including a positive effect, if any, on survival has not been demonstrated. Extension studies are underway.
Tofersen joins three other FDA-approved ALS therapies:
• Riluzole, an oral drug available since 1995 that slows disease progression by blocking glutamate.
• Edaravone, an antioxidant approved in 2017, administered orally or intravenously.
• An orally administered combination of sodium phenylbutyrate and taurursodiol marketed as Relyvrio and formerly known as AMX0035, that was introduced in 2022.
“We offer riluzole, which is safe in combination with other therapies, to most patients,” said Dr. Scelsa, who noted that treatment trials often test experimental drugs on top of riluzole. He moves to edaravone or Relyvrio, which are far more expensive, selectively. Tofersen, which is also expensive, is reserved for patients with SOD1-associated disease; however, not all eligible patients opt for this therapy after reviewing its benefits and risks.
“There is not yet a guarantee that tofersen will improve outcomes, and it requires intrathecal injections for life,”
Dr. Maiser said. “Some patients, particularly my older patients, have said, ‘No thank you,’ based on the available data.”
Dr. Macgowan pointed out that lumbar puncture repeated indefinitely can be “challenging.” He, too, discusses all available treatment options with every patient, including riluzole, which he agreed is associated with a meaningful benefit, particularly when started early.
Because of the safety of riluzole, Dr. Maragakis takes early treatment a step further. For neurologists who have a high level of suspicion of ALS in a given patient, “my advice would be to treat aggressively from the get-go. Even if not 100% certain of the diagnosis, I would start them on riluzole while waiting for confirmation.” Like the other experts interviewed here, he acknowledged that referral to a busy comprehensive ALS center often takes time, making it reasonable to initiate treatment when suspicion is high.
On the front lines, “the neurologist can tell the patient that ALS is just one of several potential explanations for symptoms but there is concern,” said Dr. Maragakis, proposing a strategy to introduce the possibility of ALS and start treatment that might slow disease while waiting for confirmation of the diagnosis. “My biggest concern is that no one is making that call,” he said, trying to address at least one reason for the current delay in making referrals.
Comprehensive care at specialty centers
Whenever possible, ALS is a disease best managed at a center that offers comprehensive management, including multidisciplinary care. On this point, the four experts agreed.
“Tertiary-care centers for ALS serve a critical purpose,”
Dr. Maiser said. For a disease that affects nearly every aspect of life, the skills of a multidisciplinary support staff offer an “opportunity to stay in front of the disease” for as long as possible. Teamwork often leads to “outside-of-the-box thinking” for helping patients and families cope with the range of disabilities that undermine the patient’s quality of life.
Details of ALS management matter. At Mount Sinai and Hennepin Healthcare, and at Johns Hopkins, where demand recently led to the opening of a second ALS clinic, the ALS center is set up to address the full spectrum of needs. Staff members have multiple skills so that they can work together to make patients comfortable and prepare them for what is inevitably progression – even if the rate of that progression varies.
All these centers incorporate a rational, thorough discussion of end-of-life options in a palliative care approach that targets optimized quality of life. One goal is to prepare patients to consider and be prepared to make decisions when it is time for tracheostomy, percutaneous endoscopic gastrostomy, and other life support options that are not always well tolerated. The goal? Avoiding unnecessary anguish during end-stage disease when impaired respiratory function – the primary cause of ALS-related death – no longer sustains unassisted survival.
“I am concerned for the many ALS patients without access to this type of comprehensive care,” Dr. Macgowan said.
Like the other experts here, he emphasized that the demands of ALS care can be “overwhelming” outside a comprehensive care setting – for the patient, their family, and individual providers.
Looking ahead
There are many reasons to be optimistic about improving the survival and care of patients with ALS. Besides therapies in clinical trials, Dr. Scelsa explained, there is the potential role for monitoring neurofilament light changes, a biomarker of neurodegeneration, in patients who are at risk of ALS.
Dr. Maragakis offered an analogy to the gene therapy onasemnogene abeparvovec, which can prevent the associated neurodegeneration of spinal muscular atrophy if initiated before symptoms appear. He said that, in ALS, neurofilament light changes or other biomarkers might offer an opportunity to halt the progression of disease before it starts – if one or more therapies in development prove workable.
In the meantime, neurologists who do not specialize in ALS should be thinking about how they can participate in speedier diagnostic pathways.
“There are a number of therapies that look promising,” Dr. Maiser told Rare Neurological Disease Special Report. He singled out strategies to degrade TDP-43 or prevent it from forming. If these treatments are found effective, it’s expected that they would be of value in sporadic ALS, the most common form. Again, though, “the challenge is getting patients on this therapy at the earliest stages of disease.”
Dr. Maragakis discloses equity ownership/stock options with Braintrust Bio and Akava; he is a patent holder with Johns Hopkins [ALS] and has received grant/research/clinical trial support from Apellis Pharma, Biogen Idec, Cytokinetics, Helixmith, Calico, Sanofi, Department of Defense ALSRP, Maryland Stem Cell Research Fund, Massachusetts General Hospital, Medicinova, and NINDS. He serves as consultant or advisory board member for Amylyx; Cytokinetics, Roche, Healey Center, Nura Bio, Northeast ALS Consortium, Akava, Inflammx, and Secretome. Dr. Scelsa did not report any conflicts of interest. Dr. Macgowan and Dr. Maiser have no relevant conflicts of interest to disclose.
References
1. Mehta P et al. Prevalence of amyotrophic lateral sclerosis in the United States using established and novel methodologies, 2017. Amyotroph Lateral Scler Frontotemporal Degener. 2023;24(1-2):108-16. doi: 10.1080/21678421.2022.2059380.
2. Mead RJ et al. Amyotrophic lateral sclerosis: A neurodegenerative disorder poised for successful therapeutic translation. Nat Rev Drug Discov. 2023;22(3):185-212. doi: 10.1038/s41573-022-00612-2.
3. Longinetti E and Fang F. Epidemiology of amyotrophic lateral sclerosis: An update of recent literature. Curr Opin Neurol. 2019;32(5):771-6. doi: 10.1097/WCO.0000000000000730.
4. van den Bos MAJ et al. Pathophysiology and diagnosis of ALS: Insights from advances in neurophysiological techniques. Int J Mol Sci. 2019;20(11):2818. doi: 10.3390/ijms20112818.
5. Neumann M et al. Ubiquitinated TDP-43 in frontotemporal lobar degeneration and amyotrophic lateral sclerosis. Science. 2006;314(5796):130-3. doi: 10.1126/science.1134108.
6. Ling S-C et al. Converging mechanisms in ALS and FTD: Disrupted RNA and protein homeostasis. Neuron. 2013;79(3):416-38. doi: 10.1016/j.neuron.2013.07.033.
7. Ranganathan R et al. Multifaceted genes in amyotrophic lateral sclerosis-frontotemporal dementia. Front Neurosci. 2020;14:684. doi: 10.3389/fnins.2020.00684.
8. Ryan M et al. Lifetime risk and heritability of amyotrophic lateral sclerosis. JAMA Neurol. 2019;76(11):1367-74. doi: 10.1001/jamaneurol.2019.2044.
9. van Rheenen W et al. Common and rare variant association analyses in amyotrophic lateral sclerosis identify 15 risk loci with distinct genetic architectures and neuron-specific biology. Nat Genet. 2021;53(12):1636-48. doi: 10.1038/s41588-021-00973-1.
10. Miller TM et al; VALOR and OLE Working Group. Trial of antisense oligonucleotide tofersen for SOD1 ALS. N Engl J Med. 2022;387(12):1099-110. doi: 10.1056/NEJMoa2204705.
Amyotrophic lateral sclerosis (ALS) falls easily into the Food and Drug Administration definition of “rare disease.” With an estimated prevalence in the United States of fewer than 20,000 cases,1 ALS sits comfortably below the cutoff of 200,000 cases that serves to define a disease as “rare.”
After a recent steep climb, there are something on the order of 50 therapies, across more than 10 drug classes, in clinical trials for the treatment of ALS.2 This bounty represents exciting progress toward the development of targeted therapies for a characteristically fatal disease.
That headway is coupled with a sobering limitation, however: Relatively few ALS patients are being enrolled.
The knotty problem with therapeutic trials for ALS
“Trials are generally designed for patients with adequate functional reserve and predicted survival, to ensure that a signal of benefit can be seen,” said Nicholas John Maragakis, MD, director of the ALS Clinical Trials Unit at Johns Hopkins University, Baltimore. “Many of my patients are too severely affected at presentation.”
Dr. Maragakis hasn’t calculated the precise percentage of patients he is enrolling in one of the many available trials available at the Johns Hopkins center. He estimates that it is less than 20%, however.
That percentage is comparable to what is reported by Stephen Scelsa, MD, and Daniel J. Macgowan, MD, who share much of the ALS caseload in a dedicated, comprehensive ALS center at Mount Sinai Beth Israel, New York. Both are on the faculty at the Icahn School of Medicine at Mount Sinai.
“The considerable delay in the diagnosis of ALS remains a challenge,” Dr. Scelsa acknowledges. Like Dr. Maragakis, he reports that, by the time patients develop symptoms that make referral to a comprehensive ALS center like Mount Sinai Beth Israel appropriate, many no longer meet eligibility criteria for most experimental treatments.
Some therapeutic targets in clinical trials, such as neuroinflammation, offer potential benefit even in advancing disease, but it is prevention that is usually the goal of experimental ALS therapies. This approach is associated with far more promise than attempting to reverse existing neurologic damage, which might not be possible, according to both Dr. Scelsa and Dr. Macgowan.
“The clinical trials are typically looking for patients with less than 2 years since the onset of symptoms and at least 60% of predicted respiratory function,” Dr. Macgowan said.
Because of these or other similarly restrictive criteria, coupled with common delays before patients arrive at a center where trials are available, “the window for clinical research closes very quickly,” Dr. Macgowan added, and “the band of patients who are eligible is relatively narrow.”
At Hennepin Healthcare in Minneapolis, which, like Johns Hopkins and Mount Sinai, offers an advanced multidisciplinary approach to ALS care in a dedicated clinic, the problem of late referrals is no different. Samuel Maiser, MD, chair of neurology, does attempt to counter this delay by moving quickly.
“I almost always offer a therapeutic trial to a patient with early-stage ALS,” he said. He does so earlier, rather than later, and explains: “I do not want to delay that conversation, because any delay might reduce the chance for getting into a trial.”
The generalist can make a difference in therapeutic success
The proliferation of clinical trials has made early diagnosis of ALS urgent. However, the experts interviewed for this article agreed: Accelerating the time to diagnosis is more dependent on the general neurologist or primary care physician than on the ALS specialist. ALS is a diagnosis of exclusion, but there is now very little delay in reaching a probable diagnosis at a dedicated center.
Yet neurodegenerative complaints in early-stage ALS are often nonspecific and mild; confidence in making a potential diagnosis of ALS is limited among primary care clinicians and general neurologists, who almost always see these patients first. Usually, the problem is not failure to include ALS in the differential diagnosis but hesitation in being candid when there is still doubt.
General neurologists, in particular, Dr. Maragakis said, “are often highly suspicious of a diagnosis of ALS very early on but are concerned about using this term until the clinical signs are more compelling.”
This is understandable. There is reluctance to deliver bad news when confidence in the diagnosis is limited. But the experts agreed: Delayed diagnosis is not in the patient’s interest now that there is at least the potential for entering a trial supported by a scientific rationale for benefit.
“Waiting for 100% certainty – this could actually harm our patients,” Dr. Maiser said. The tendency to avoid delivering bad news, he said, “is human nature, and it is not easy to tell people that ALS is the potential cause, but it’s important for early treatment.”
Some evidence suggests that the incidence of ALS is increasing3 but this is not necessarily evident at the clinical level. “It is not my impression that the incidence of ALS is increasing,” Dr. Macgowan said, “so much as I think we are getting better at making the diagnosis.”
Where we stand: Pathophysiology, diagnosis, treatment
Pathophysiology. ALS is characterized by muscle denervation.4 In the great majority of cases, the disease represents a proteinopathy involving loss of the TDP-43 protein from nuclei. However, pathological heterogeneity means that other pathophysiological mechanisms – mediated by oxidative stress, mitochondrial dysfunction, and neurotoxicity related to excessive stimulation of postsynaptic glutamate receptors – can participate.2,5,6
Approximately 10% of patients have a known gene associated with ALS.7 The rest have what is considered sporadic ALS, although some experts estimate that heritability will eventually be confirmed in 50% or more of cases that have been given the “sporadic” label.8,9 More than 30 genes have been linked to ALS in genomewide association studies. Among patients whose disease carries a known familial link, four genes – SOD1, TARDBP, FUS, and C9orf72 – account for approximately 70% of cases.2
Diagnosis. Genetic testing in patients with suspected or confirmed ALS is the standard of care at most, if not all, comprehensive ALS treatment centers, according to the four experts interviewed by Neurology Reviews 2023 Rare Neurological Disease Special Report for this article. Such testing was routine for years because of its potential for helping researchers to understand subtypes of disease; today, testing has assumed even greater practical value with recent approval of the first ALS gene therapy: Tofersen (Qalsody, Biogen), licensed in 2023, is an antisense oligonucleotide therapy that targets SOD1 mRNA to reduce production of the SOD1 protein, a mediator of disease progression.
“Genetic testing has been useful for telling us something about the disease and its prognosis,” Dr. Maragakis said, “but an approved gene therapy means it can have a direct effect on treatment.”
ALS therapeutics. Other gene therapies are in development. Gene signatures are likely to provide even more opportunities for clinical trials in the future.
Following three loading doses of tofersen at 14-day intervals, the maintenance regimen, administered intrathecally by lumbar puncture, is every 28 days. In the phase 3 trial, tofersen reduced levels of SOD1 protein and neurofilament light chain, a biomarker of axonal injury.10 Tofersen is appropriate only in patients with SOD1-associated ALS; the drug’s favorable clinical impact, including a positive effect, if any, on survival has not been demonstrated. Extension studies are underway.
Tofersen joins three other FDA-approved ALS therapies:
• Riluzole, an oral drug available since 1995 that slows disease progression by blocking glutamate.
• Edaravone, an antioxidant approved in 2017, administered orally or intravenously.
• An orally administered combination of sodium phenylbutyrate and taurursodiol marketed as Relyvrio and formerly known as AMX0035, that was introduced in 2022.
“We offer riluzole, which is safe in combination with other therapies, to most patients,” said Dr. Scelsa, who noted that treatment trials often test experimental drugs on top of riluzole. He moves to edaravone or Relyvrio, which are far more expensive, selectively. Tofersen, which is also expensive, is reserved for patients with SOD1-associated disease; however, not all eligible patients opt for this therapy after reviewing its benefits and risks.
“There is not yet a guarantee that tofersen will improve outcomes, and it requires intrathecal injections for life,”
Dr. Maiser said. “Some patients, particularly my older patients, have said, ‘No thank you,’ based on the available data.”
Dr. Macgowan pointed out that lumbar puncture repeated indefinitely can be “challenging.” He, too, discusses all available treatment options with every patient, including riluzole, which he agreed is associated with a meaningful benefit, particularly when started early.
Because of the safety of riluzole, Dr. Maragakis takes early treatment a step further. For neurologists who have a high level of suspicion of ALS in a given patient, “my advice would be to treat aggressively from the get-go. Even if not 100% certain of the diagnosis, I would start them on riluzole while waiting for confirmation.” Like the other experts interviewed here, he acknowledged that referral to a busy comprehensive ALS center often takes time, making it reasonable to initiate treatment when suspicion is high.
On the front lines, “the neurologist can tell the patient that ALS is just one of several potential explanations for symptoms but there is concern,” said Dr. Maragakis, proposing a strategy to introduce the possibility of ALS and start treatment that might slow disease while waiting for confirmation of the diagnosis. “My biggest concern is that no one is making that call,” he said, trying to address at least one reason for the current delay in making referrals.
Comprehensive care at specialty centers
Whenever possible, ALS is a disease best managed at a center that offers comprehensive management, including multidisciplinary care. On this point, the four experts agreed.
“Tertiary-care centers for ALS serve a critical purpose,”
Dr. Maiser said. For a disease that affects nearly every aspect of life, the skills of a multidisciplinary support staff offer an “opportunity to stay in front of the disease” for as long as possible. Teamwork often leads to “outside-of-the-box thinking” for helping patients and families cope with the range of disabilities that undermine the patient’s quality of life.
Details of ALS management matter. At Mount Sinai and Hennepin Healthcare, and at Johns Hopkins, where demand recently led to the opening of a second ALS clinic, the ALS center is set up to address the full spectrum of needs. Staff members have multiple skills so that they can work together to make patients comfortable and prepare them for what is inevitably progression – even if the rate of that progression varies.
All these centers incorporate a rational, thorough discussion of end-of-life options in a palliative care approach that targets optimized quality of life. One goal is to prepare patients to consider and be prepared to make decisions when it is time for tracheostomy, percutaneous endoscopic gastrostomy, and other life support options that are not always well tolerated. The goal? Avoiding unnecessary anguish during end-stage disease when impaired respiratory function – the primary cause of ALS-related death – no longer sustains unassisted survival.
“I am concerned for the many ALS patients without access to this type of comprehensive care,” Dr. Macgowan said.
Like the other experts here, he emphasized that the demands of ALS care can be “overwhelming” outside a comprehensive care setting – for the patient, their family, and individual providers.
Looking ahead
There are many reasons to be optimistic about improving the survival and care of patients with ALS. Besides therapies in clinical trials, Dr. Scelsa explained, there is the potential role for monitoring neurofilament light changes, a biomarker of neurodegeneration, in patients who are at risk of ALS.
Dr. Maragakis offered an analogy to the gene therapy onasemnogene abeparvovec, which can prevent the associated neurodegeneration of spinal muscular atrophy if initiated before symptoms appear. He said that, in ALS, neurofilament light changes or other biomarkers might offer an opportunity to halt the progression of disease before it starts – if one or more therapies in development prove workable.
In the meantime, neurologists who do not specialize in ALS should be thinking about how they can participate in speedier diagnostic pathways.
“There are a number of therapies that look promising,” Dr. Maiser told Rare Neurological Disease Special Report. He singled out strategies to degrade TDP-43 or prevent it from forming. If these treatments are found effective, it’s expected that they would be of value in sporadic ALS, the most common form. Again, though, “the challenge is getting patients on this therapy at the earliest stages of disease.”
Dr. Maragakis discloses equity ownership/stock options with Braintrust Bio and Akava; he is a patent holder with Johns Hopkins [ALS] and has received grant/research/clinical trial support from Apellis Pharma, Biogen Idec, Cytokinetics, Helixmith, Calico, Sanofi, Department of Defense ALSRP, Maryland Stem Cell Research Fund, Massachusetts General Hospital, Medicinova, and NINDS. He serves as consultant or advisory board member for Amylyx; Cytokinetics, Roche, Healey Center, Nura Bio, Northeast ALS Consortium, Akava, Inflammx, and Secretome. Dr. Scelsa did not report any conflicts of interest. Dr. Macgowan and Dr. Maiser have no relevant conflicts of interest to disclose.
References
1. Mehta P et al. Prevalence of amyotrophic lateral sclerosis in the United States using established and novel methodologies, 2017. Amyotroph Lateral Scler Frontotemporal Degener. 2023;24(1-2):108-16. doi: 10.1080/21678421.2022.2059380.
2. Mead RJ et al. Amyotrophic lateral sclerosis: A neurodegenerative disorder poised for successful therapeutic translation. Nat Rev Drug Discov. 2023;22(3):185-212. doi: 10.1038/s41573-022-00612-2.
3. Longinetti E and Fang F. Epidemiology of amyotrophic lateral sclerosis: An update of recent literature. Curr Opin Neurol. 2019;32(5):771-6. doi: 10.1097/WCO.0000000000000730.
4. van den Bos MAJ et al. Pathophysiology and diagnosis of ALS: Insights from advances in neurophysiological techniques. Int J Mol Sci. 2019;20(11):2818. doi: 10.3390/ijms20112818.
5. Neumann M et al. Ubiquitinated TDP-43 in frontotemporal lobar degeneration and amyotrophic lateral sclerosis. Science. 2006;314(5796):130-3. doi: 10.1126/science.1134108.
6. Ling S-C et al. Converging mechanisms in ALS and FTD: Disrupted RNA and protein homeostasis. Neuron. 2013;79(3):416-38. doi: 10.1016/j.neuron.2013.07.033.
7. Ranganathan R et al. Multifaceted genes in amyotrophic lateral sclerosis-frontotemporal dementia. Front Neurosci. 2020;14:684. doi: 10.3389/fnins.2020.00684.
8. Ryan M et al. Lifetime risk and heritability of amyotrophic lateral sclerosis. JAMA Neurol. 2019;76(11):1367-74. doi: 10.1001/jamaneurol.2019.2044.
9. van Rheenen W et al. Common and rare variant association analyses in amyotrophic lateral sclerosis identify 15 risk loci with distinct genetic architectures and neuron-specific biology. Nat Genet. 2021;53(12):1636-48. doi: 10.1038/s41588-021-00973-1.
10. Miller TM et al; VALOR and OLE Working Group. Trial of antisense oligonucleotide tofersen for SOD1 ALS. N Engl J Med. 2022;387(12):1099-110. doi: 10.1056/NEJMoa2204705.
Amyotrophic lateral sclerosis (ALS) falls easily into the Food and Drug Administration definition of “rare disease.” With an estimated prevalence in the United States of fewer than 20,000 cases,1 ALS sits comfortably below the cutoff of 200,000 cases that serves to define a disease as “rare.”
After a recent steep climb, there are something on the order of 50 therapies, across more than 10 drug classes, in clinical trials for the treatment of ALS.2 This bounty represents exciting progress toward the development of targeted therapies for a characteristically fatal disease.
That headway is coupled with a sobering limitation, however: Relatively few ALS patients are being enrolled.
The knotty problem with therapeutic trials for ALS
“Trials are generally designed for patients with adequate functional reserve and predicted survival, to ensure that a signal of benefit can be seen,” said Nicholas John Maragakis, MD, director of the ALS Clinical Trials Unit at Johns Hopkins University, Baltimore. “Many of my patients are too severely affected at presentation.”
Dr. Maragakis hasn’t calculated the precise percentage of patients he is enrolling in one of the many available trials available at the Johns Hopkins center. He estimates that it is less than 20%, however.
That percentage is comparable to what is reported by Stephen Scelsa, MD, and Daniel J. Macgowan, MD, who share much of the ALS caseload in a dedicated, comprehensive ALS center at Mount Sinai Beth Israel, New York. Both are on the faculty at the Icahn School of Medicine at Mount Sinai.
“The considerable delay in the diagnosis of ALS remains a challenge,” Dr. Scelsa acknowledges. Like Dr. Maragakis, he reports that, by the time patients develop symptoms that make referral to a comprehensive ALS center like Mount Sinai Beth Israel appropriate, many no longer meet eligibility criteria for most experimental treatments.
Some therapeutic targets in clinical trials, such as neuroinflammation, offer potential benefit even in advancing disease, but it is prevention that is usually the goal of experimental ALS therapies. This approach is associated with far more promise than attempting to reverse existing neurologic damage, which might not be possible, according to both Dr. Scelsa and Dr. Macgowan.
“The clinical trials are typically looking for patients with less than 2 years since the onset of symptoms and at least 60% of predicted respiratory function,” Dr. Macgowan said.
Because of these or other similarly restrictive criteria, coupled with common delays before patients arrive at a center where trials are available, “the window for clinical research closes very quickly,” Dr. Macgowan added, and “the band of patients who are eligible is relatively narrow.”
At Hennepin Healthcare in Minneapolis, which, like Johns Hopkins and Mount Sinai, offers an advanced multidisciplinary approach to ALS care in a dedicated clinic, the problem of late referrals is no different. Samuel Maiser, MD, chair of neurology, does attempt to counter this delay by moving quickly.
“I almost always offer a therapeutic trial to a patient with early-stage ALS,” he said. He does so earlier, rather than later, and explains: “I do not want to delay that conversation, because any delay might reduce the chance for getting into a trial.”
The generalist can make a difference in therapeutic success
The proliferation of clinical trials has made early diagnosis of ALS urgent. However, the experts interviewed for this article agreed: Accelerating the time to diagnosis is more dependent on the general neurologist or primary care physician than on the ALS specialist. ALS is a diagnosis of exclusion, but there is now very little delay in reaching a probable diagnosis at a dedicated center.
Yet neurodegenerative complaints in early-stage ALS are often nonspecific and mild; confidence in making a potential diagnosis of ALS is limited among primary care clinicians and general neurologists, who almost always see these patients first. Usually, the problem is not failure to include ALS in the differential diagnosis but hesitation in being candid when there is still doubt.
General neurologists, in particular, Dr. Maragakis said, “are often highly suspicious of a diagnosis of ALS very early on but are concerned about using this term until the clinical signs are more compelling.”
This is understandable. There is reluctance to deliver bad news when confidence in the diagnosis is limited. But the experts agreed: Delayed diagnosis is not in the patient’s interest now that there is at least the potential for entering a trial supported by a scientific rationale for benefit.
“Waiting for 100% certainty – this could actually harm our patients,” Dr. Maiser said. The tendency to avoid delivering bad news, he said, “is human nature, and it is not easy to tell people that ALS is the potential cause, but it’s important for early treatment.”
Some evidence suggests that the incidence of ALS is increasing3 but this is not necessarily evident at the clinical level. “It is not my impression that the incidence of ALS is increasing,” Dr. Macgowan said, “so much as I think we are getting better at making the diagnosis.”
Where we stand: Pathophysiology, diagnosis, treatment
Pathophysiology. ALS is characterized by muscle denervation.4 In the great majority of cases, the disease represents a proteinopathy involving loss of the TDP-43 protein from nuclei. However, pathological heterogeneity means that other pathophysiological mechanisms – mediated by oxidative stress, mitochondrial dysfunction, and neurotoxicity related to excessive stimulation of postsynaptic glutamate receptors – can participate.2,5,6
Approximately 10% of patients have a known gene associated with ALS.7 The rest have what is considered sporadic ALS, although some experts estimate that heritability will eventually be confirmed in 50% or more of cases that have been given the “sporadic” label.8,9 More than 30 genes have been linked to ALS in genomewide association studies. Among patients whose disease carries a known familial link, four genes – SOD1, TARDBP, FUS, and C9orf72 – account for approximately 70% of cases.2
Diagnosis. Genetic testing in patients with suspected or confirmed ALS is the standard of care at most, if not all, comprehensive ALS treatment centers, according to the four experts interviewed by Neurology Reviews 2023 Rare Neurological Disease Special Report for this article. Such testing was routine for years because of its potential for helping researchers to understand subtypes of disease; today, testing has assumed even greater practical value with recent approval of the first ALS gene therapy: Tofersen (Qalsody, Biogen), licensed in 2023, is an antisense oligonucleotide therapy that targets SOD1 mRNA to reduce production of the SOD1 protein, a mediator of disease progression.
“Genetic testing has been useful for telling us something about the disease and its prognosis,” Dr. Maragakis said, “but an approved gene therapy means it can have a direct effect on treatment.”
ALS therapeutics. Other gene therapies are in development. Gene signatures are likely to provide even more opportunities for clinical trials in the future.
Following three loading doses of tofersen at 14-day intervals, the maintenance regimen, administered intrathecally by lumbar puncture, is every 28 days. In the phase 3 trial, tofersen reduced levels of SOD1 protein and neurofilament light chain, a biomarker of axonal injury.10 Tofersen is appropriate only in patients with SOD1-associated ALS; the drug’s favorable clinical impact, including a positive effect, if any, on survival has not been demonstrated. Extension studies are underway.
Tofersen joins three other FDA-approved ALS therapies:
• Riluzole, an oral drug available since 1995 that slows disease progression by blocking glutamate.
• Edaravone, an antioxidant approved in 2017, administered orally or intravenously.
• An orally administered combination of sodium phenylbutyrate and taurursodiol marketed as Relyvrio and formerly known as AMX0035, that was introduced in 2022.
“We offer riluzole, which is safe in combination with other therapies, to most patients,” said Dr. Scelsa, who noted that treatment trials often test experimental drugs on top of riluzole. He moves to edaravone or Relyvrio, which are far more expensive, selectively. Tofersen, which is also expensive, is reserved for patients with SOD1-associated disease; however, not all eligible patients opt for this therapy after reviewing its benefits and risks.
“There is not yet a guarantee that tofersen will improve outcomes, and it requires intrathecal injections for life,”
Dr. Maiser said. “Some patients, particularly my older patients, have said, ‘No thank you,’ based on the available data.”
Dr. Macgowan pointed out that lumbar puncture repeated indefinitely can be “challenging.” He, too, discusses all available treatment options with every patient, including riluzole, which he agreed is associated with a meaningful benefit, particularly when started early.
Because of the safety of riluzole, Dr. Maragakis takes early treatment a step further. For neurologists who have a high level of suspicion of ALS in a given patient, “my advice would be to treat aggressively from the get-go. Even if not 100% certain of the diagnosis, I would start them on riluzole while waiting for confirmation.” Like the other experts interviewed here, he acknowledged that referral to a busy comprehensive ALS center often takes time, making it reasonable to initiate treatment when suspicion is high.
On the front lines, “the neurologist can tell the patient that ALS is just one of several potential explanations for symptoms but there is concern,” said Dr. Maragakis, proposing a strategy to introduce the possibility of ALS and start treatment that might slow disease while waiting for confirmation of the diagnosis. “My biggest concern is that no one is making that call,” he said, trying to address at least one reason for the current delay in making referrals.
Comprehensive care at specialty centers
Whenever possible, ALS is a disease best managed at a center that offers comprehensive management, including multidisciplinary care. On this point, the four experts agreed.
“Tertiary-care centers for ALS serve a critical purpose,”
Dr. Maiser said. For a disease that affects nearly every aspect of life, the skills of a multidisciplinary support staff offer an “opportunity to stay in front of the disease” for as long as possible. Teamwork often leads to “outside-of-the-box thinking” for helping patients and families cope with the range of disabilities that undermine the patient’s quality of life.
Details of ALS management matter. At Mount Sinai and Hennepin Healthcare, and at Johns Hopkins, where demand recently led to the opening of a second ALS clinic, the ALS center is set up to address the full spectrum of needs. Staff members have multiple skills so that they can work together to make patients comfortable and prepare them for what is inevitably progression – even if the rate of that progression varies.
All these centers incorporate a rational, thorough discussion of end-of-life options in a palliative care approach that targets optimized quality of life. One goal is to prepare patients to consider and be prepared to make decisions when it is time for tracheostomy, percutaneous endoscopic gastrostomy, and other life support options that are not always well tolerated. The goal? Avoiding unnecessary anguish during end-stage disease when impaired respiratory function – the primary cause of ALS-related death – no longer sustains unassisted survival.
“I am concerned for the many ALS patients without access to this type of comprehensive care,” Dr. Macgowan said.
Like the other experts here, he emphasized that the demands of ALS care can be “overwhelming” outside a comprehensive care setting – for the patient, their family, and individual providers.
Looking ahead
There are many reasons to be optimistic about improving the survival and care of patients with ALS. Besides therapies in clinical trials, Dr. Scelsa explained, there is the potential role for monitoring neurofilament light changes, a biomarker of neurodegeneration, in patients who are at risk of ALS.
Dr. Maragakis offered an analogy to the gene therapy onasemnogene abeparvovec, which can prevent the associated neurodegeneration of spinal muscular atrophy if initiated before symptoms appear. He said that, in ALS, neurofilament light changes or other biomarkers might offer an opportunity to halt the progression of disease before it starts – if one or more therapies in development prove workable.
In the meantime, neurologists who do not specialize in ALS should be thinking about how they can participate in speedier diagnostic pathways.
“There are a number of therapies that look promising,” Dr. Maiser told Rare Neurological Disease Special Report. He singled out strategies to degrade TDP-43 or prevent it from forming. If these treatments are found effective, it’s expected that they would be of value in sporadic ALS, the most common form. Again, though, “the challenge is getting patients on this therapy at the earliest stages of disease.”
Dr. Maragakis discloses equity ownership/stock options with Braintrust Bio and Akava; he is a patent holder with Johns Hopkins [ALS] and has received grant/research/clinical trial support from Apellis Pharma, Biogen Idec, Cytokinetics, Helixmith, Calico, Sanofi, Department of Defense ALSRP, Maryland Stem Cell Research Fund, Massachusetts General Hospital, Medicinova, and NINDS. He serves as consultant or advisory board member for Amylyx; Cytokinetics, Roche, Healey Center, Nura Bio, Northeast ALS Consortium, Akava, Inflammx, and Secretome. Dr. Scelsa did not report any conflicts of interest. Dr. Macgowan and Dr. Maiser have no relevant conflicts of interest to disclose.
References
1. Mehta P et al. Prevalence of amyotrophic lateral sclerosis in the United States using established and novel methodologies, 2017. Amyotroph Lateral Scler Frontotemporal Degener. 2023;24(1-2):108-16. doi: 10.1080/21678421.2022.2059380.
2. Mead RJ et al. Amyotrophic lateral sclerosis: A neurodegenerative disorder poised for successful therapeutic translation. Nat Rev Drug Discov. 2023;22(3):185-212. doi: 10.1038/s41573-022-00612-2.
3. Longinetti E and Fang F. Epidemiology of amyotrophic lateral sclerosis: An update of recent literature. Curr Opin Neurol. 2019;32(5):771-6. doi: 10.1097/WCO.0000000000000730.
4. van den Bos MAJ et al. Pathophysiology and diagnosis of ALS: Insights from advances in neurophysiological techniques. Int J Mol Sci. 2019;20(11):2818. doi: 10.3390/ijms20112818.
5. Neumann M et al. Ubiquitinated TDP-43 in frontotemporal lobar degeneration and amyotrophic lateral sclerosis. Science. 2006;314(5796):130-3. doi: 10.1126/science.1134108.
6. Ling S-C et al. Converging mechanisms in ALS and FTD: Disrupted RNA and protein homeostasis. Neuron. 2013;79(3):416-38. doi: 10.1016/j.neuron.2013.07.033.
7. Ranganathan R et al. Multifaceted genes in amyotrophic lateral sclerosis-frontotemporal dementia. Front Neurosci. 2020;14:684. doi: 10.3389/fnins.2020.00684.
8. Ryan M et al. Lifetime risk and heritability of amyotrophic lateral sclerosis. JAMA Neurol. 2019;76(11):1367-74. doi: 10.1001/jamaneurol.2019.2044.
9. van Rheenen W et al. Common and rare variant association analyses in amyotrophic lateral sclerosis identify 15 risk loci with distinct genetic architectures and neuron-specific biology. Nat Genet. 2021;53(12):1636-48. doi: 10.1038/s41588-021-00973-1.
10. Miller TM et al; VALOR and OLE Working Group. Trial of antisense oligonucleotide tofersen for SOD1 ALS. N Engl J Med. 2022;387(12):1099-110. doi: 10.1056/NEJMoa2204705.
Emerging therapies in Duchenne and facioscapulohumeral muscular dystrophy
“There have been so many breakthroughs recently on the side of genetically targeted treatment [for muscular dystrophy] that supports muscle better,” said John F. Brandsema, MD, a child neurologist and section head at Children’s Hospital of Philadelphia, in an interview with Neurology Reviews 2023 Rare Neurological Disease Special Report. “We’re starting to see clinical response to some things that have been in trials – after decades of banging our heads on the wall trying new therapies, only to see them fail. I think it’s about reframing Duchenne muscular dystrophy [DMD] and facioscapulohumeral muscular dystrophy [FSHD] as treatable by target therapy because previously, they were treated with supportive care.”
DMD: Current and emerging therapies
DMD is caused by a mutation in the dystrophin gene on the X chromosome that inhibits production of dystrophin, a protein that shields muscles from injury during contraction. Dystrophin deficiency prevents muscle recovery, resulting in muscle-cell death and, ultimately, loss of function due to muscle degeneration.
FDA-approved exon-skipping therapies. Treatment modalities for what has historically been an incurable, lifespan-shortening disease involved supportive care that addresses symptoms, not the underlying cause. Consequently, many patients with DMD live only into their 20s and 30s. The tide began to turn in 2016, however, when the U.S. Food and Drug Administration granted accelerated approval for eteplirsen, an exon 51–skipping treatment that was the first RNA-based therapy for DMD to target the underlying cause. Additional exon-skipping therapies followed, including casimersen, which skips exon 45, and golodirsen and viltolarsen, which skip exon 53.
AOC 1044: Novel exon-skipping. In April 2023, the FDA granted orphan-drug designation to the experimental drug antibody oligonucleotide conjugate (AOC) 1044 that skips exon 44. A small interfering RNA (siRNA), AOC 1044 works in patients who have a mutation amenable to exon 44 skipping (a disease type known as DMD44) by delivering phosphorodiamidate morpholino to skeletal muscle and heart tissue that skips exon 44. The process allows for dystrophin production, thereby preventing degradation of muscle tissue.
The orphan drug status of AOC 1044 made it available to the population of patients enrolled in the EXPLORE44 Phase 1/2 trial. However, studies demonstrating effectiveness of the drug – with the hope of, ultimately, providing widespread access to AOC 1044 – are still underway. In one of those studies, investigators expect to enroll approximately 40 healthy volunteers and 24 DMD44 patients 7-27 years of age.3 The study will evaluate the effects of exon skipping and dystrophin protein levels in participants who have DMD44.
Delandistrogene moxeparvovec. Oct. 27, 2021, marked the inception of the phase 3 Multinational, Randomized, Double-Blind, Placebo-Controlled Systemic Gene Delivery Study to Evaluate the Safety and Efficacy of SRP-9001 in Subjects With Duchenne Muscular Dystrophy (EMBARK). The trial is evaluating the safety and efficacy of the gene-therapy agent delandistrogene moxeparvovec in ambulatory boys who were 4 to less than 8 years of age at randomization. The 126 boys enrolled in the trial met the criteria of (1) a diagnosis of DMD confirmed by documented clinical findings and previous genetic testing and (2) a pathogenic frameshift mutation stop codon located between exons 18 and 79 (inclusive), except for a mutation fully contained within exon 45.
Additional inclusion criteria were (1) the ability to cooperate with motor-assessment testing and (2) receiving a steady daily dose of oral corticosteroid for 12 weeks or longer prior to screening, and (3) the expectation of maintaining the study dosage throughout screening. Boys who had previously received gene therapy, investigational medication, or any treatment that could have amplified dystrophin expression within the time limit specified by the protocol were ineligible to participate. Boys were excluded from the study if they presented with any other illness, medical condition, or need for chronic drug treatment.
Exon-skipping therapies in trials. Various biotech and pharmaceutical companies have initiated clinical trials to explore the potential of additional exon-skipping therapies for the DMD population:
ENTR-601-44 is another exon 44–skipping therapy in the pipeline.
On Aug. 22, 2023, the FDA approved delandistrogene moxeparvovec-rokl, a recombinant gene therapy utilizing an adenovirus vector. The product is indicated for ambulatory patients with DMD 4-5 years of age who have a confirmed mutation of the dystrophin gene.
Dyne Therapeutics is actively recruiting participants to investigate Dyne 251, its exon 51–skipping therapy.
Trials are in the works by BioMarin Pharmaceutical for its next-generation peptide-conjugated phosphorodiamidate morpholino oligomers (PPMO) for skipping exon 51.
Despite the prospects of such therapy, therapeutic targeting of exon 44 addresses only patients with DMD44, who account for approximately 10% of the DMD population. Disease involving the most prevalent site of a dystrophin gene mutation, exon 51, affects 13% of the DMD population. This leaves the majority of patients with DMD without gene therapy. Yet Dr. Brandsema is optimistic nevertheless.
“We were just failing over and over again with DMD treatment, but there is some hope now,” Dr. Brandsema said. “Also, FSHD is right on the cusp of having new therapies approaching.”
FSHD: Emerging therapies
The third more common type of muscular dystrophy is not a life-threatening condition. FSHD affects approximately 4 of every 100,000 people.1 An autosomal-dominant condition, FSHD is ultimately caused by inappropriate expression of the DUX4 protein product – a consequence of a complex genetic activity involving DUX4, its chromosomal locus, and the number of repeats of a microsatellite called D4Z4.4 The disease usually starts in proximal regions of the face (that is, surrounding the eyes and mouth), before spreading to muscular groups of the limbs – most prominently, muscles of the scapulae and humeri. Symptoms usually appear in these places initially, but the condition can affect any part of the body. Fifty percent of FSHD patients experience loss of high-frequency hearing and present with retinovasculopathy. Like DMD, FSHD varies in severity, with some forms presenting at birth.
AOC 1020-CS1 is an example of a new FSHD treatment under investigation. The phase 1/2 FORTITUDE trial is a randomized, double-blind, placebo-controlled study exploring the safety, tolerability, pharmacokinetics, pharmacodynamics, and potential efficacy of single- and multiple-dose AOC 1020-CS1 therapy in FSHD.5 The trial began in April 2023; estimated completion date is September 2025.
As with many rare diseases, however, following patients and capturing data that fully narrate their story remains challenging in both DMD and FSHD. Although clinical trials undoubtedly offer hope of expanding treatment options and additional insights into disease-state management, the often insidious, complex nature of some rare diseases, such as DMD and FSHD, presents some limitations.
“Patients are hard to measure,” Dr. Brandsema explained, “because they’re so variable at baseline in history and progress in a different [slower] way than timelines are set up in our system to study drugs.”
Neonatal screening and early diagnosis: Imperative for improving outcomes
Neonatal screening helps with early detection and treatment. Prompt diagnosis does not necessarily prolong a DMD patient’s life, but it can enhance their quality of life.
DNA diagnostics. A critical component of the path to treatment is DNA diagnostics. According to Barry J. Byrne, MD, PhD, chief medical advisor of the Muscular Dystrophy Association, the Human Genome Project conducted by the National Institutes of Health helped make DNA tests affordable; such tests run about $800 today. However, given continuous advancements in sequencing, Dr. Byrne said that whole-exome sequencing for $100 is within reach.
In terms of accessibility, some nations – Canada is an example – include testing as part of national health care services. In the United States, coverage for testing varies by health insurance plan. In addition, some plans have favored rapid diagnostic testing, and the overall cost is often individualized to the patient.
Early diagnosis and supportive care. Early diagnosis can certainly help improve DMD patients’ quality of life; supportive care provides some benefit. Dr. Byrne stressed the importance of managing extraskeletal clinical manifestations in this patient population. A critical area is initiating cardiovascular treatment immediately following diagnosis, even if the patient does not exhibit cardiovascular symptoms.
“Cardiac manifestations are actually the cause of mortality in DMD, and most boys with DMD should begin cardiovascular treatment shortly after diagnosis,” Dr. Byrne told Neurology Reviews 2023 Rare Neurological Disease Special Report. “The message to neurologists is that these patients can benefit from early cardiovascular treatment because we can prevent the complications of DMD-related heart failure until much later in life.”
Historically, clinicians used echocardiography as the mainstay tool to assess cardiovascular function; however, more and more clinicians are turning to magnetic resonance imaging for such investigation. Dr. Byrne, a cardiologist, explained that magnetic resonance imaging identifies cardiovascular dysfunction at earlier stages than echocardiography can. In addition, although DMD patients frequently experience fatigue, Dr. Byrne cautions neurologists that fatigue is usually related to muscle weakness, not necessarily heart failure.
DMD therapies carry a hefty price
Right now, the projected price range of AOC 1044 is $3.2 million to $3.4 million. Akin to the case with onasemnogene abeparvovec-xioi (Zolgensma) for spinal muscular atrophy, the world’s first gene therapy and first seven-figure drug, the manufacturer of AOC 1044 based pricing on the anticipated cost of treating a DMD44 patient throughout the lifespan, according to Dr. Byrne.
Delandistrogene moxeparvovec might come with an even higher price tag. A cost-effectiveness analysis study priced the therapy at $5 million. In a presentation to investors, the manufacturer projected the price in the range of $5 million to $13 million.6,7
‘It takes a village’: Comprehensive care requires a multidisciplinary team
Dr. Brandsema and Dr. Byrne agree: Optimizing outcomes requires ongoing coordinated and collaborative efforts of an interdisciplinary team of health care providers for the duration of DMD and FSHD patients’ lifespan.
A neurologist by training, Dr. Brandsema recognizes the importance of interdisciplinary collaboration in caring for patients with DMD, given the multiorgan manifestations of the disease.
“We have some hope with DMD, and FSHD is right on the cusp of having new therapies approaching ... It is important to recognize that interdisciplinary follow-up and optimized standard of care are important after dosing.”
“I think many patients living with neurological disorders have multiple providers they rely on for care,” Dr. Byrne said, “but cardiovascular and pulmonary care are important because both are affected in the case of DMD – not so much in FSHD.”
Ultimately, advancements in therapy and care give patients living with these disorders, and their caregivers, a renewed sense of hope – hope that their life will be improved by breakthrough therapies that have been approved or will arrive soon.
Dr. Brandsema discloses he is a consultant for Alexion, Audentes, AveXis/Novartis, Biogen, Cytokinetics, Dyne, Edgewise, Fibrogen, Genentech/Roche, Janssen, Marathon, Momenta, NS Pharma, PTC Therapeutics, Sarepta, Scholar Rock, Takeda, and WaVe. He is a speaker for AveXis and Biogen, a medical advisory council member for Cure SMA, and a site investigator for clinical trials with Alexion, Astellas, AveXis/Novartis, Biogen, Catabasis, CSL Behring, Cytokinetics, Fibrogen, Genentech/Roche, Ionis, Lilly, Janssen, Pfizer, PTC Therapeutics, Sarepta, Scholar Rock, Summit, and WaVe. Dr. Byrne has no relevant financial disclosures.
References
1. Centers for Disease Control and Prevention. What is muscular dystrophy? Updated Nov. 21, 2022. Accessed Sept. 3, 2023. https://www.cdc.gov/ncbddd/musculardystrophy/facts.html.
2. FDA approves first gene therapy for treatment of certain patients with Duchenne muscular dystrophy. U.S. Food and Drug Administration. Press release. June 22, 2023. Accessed Sept. 3, 2023. https://www.fda.gov/news-events/press-announcements/fda-approves-first-gene-therapy-treatment-certain-patients-duchenne-muscular-dystrophy.
3. Study of AOC 1044 in healthy adult volunteers and participants with Duchenne muscular dystrophy (DMD) mutations amenable to exon 44 skipping (EXPLORE44). ClinicalTrials.gov Identifier: NCT05670730. Updated April 4, 2023. Accessed Sep. 3, 2023. https://www.clinicaltrials.gov/study/NCT05670730?cond=DMD&intr=AOC%201044&rank=1.
4. Statland JM, Tawil R. Facioscapulohumeral muscular dystrophy. Continuum (Minneap. Minn). 2016;22(6, Muscle and Neuromuscular Junction Disorders):1916-31. doi: 10.1212/CON.0000000000000399.
5. Phase 1/2 study of AOC 1020 in adults with facioscapulohumeral muscular dystrophy (FSHD) (FORTITUDE). ClinicalTrials.gov Identifier: NCT05747924. Updated Aug. 9, 2023. Accessed Sept. 3, 2023. https://clinicaltrials.gov/study/NCT05747924?term=fORTITUDE&cond=Facioscapulohumeral%20Muscular%20Dystrophy&rank=1.
6. Klimchak AC, Sedita LE, Rodino-Klapac LR, et al. Assessing the value of delandistrogene moxeparvovec (SRP-9001) gene therapy in patients with Duchenne muscular dystrophy in the United States. J Mark Access Health Policy. 2023;11(1):2216518. doi: 10.1080/20016689.2023.2216518.
7. Ingram D. [Investor relations presentation.] Sarepta Therapeutics website. June 22, 2023. Accessed Sept. 3, 2023. https://investorrelations.sarepta.com/static-files/7216948c-f688-4024-922e-39761bc7a984.
“There have been so many breakthroughs recently on the side of genetically targeted treatment [for muscular dystrophy] that supports muscle better,” said John F. Brandsema, MD, a child neurologist and section head at Children’s Hospital of Philadelphia, in an interview with Neurology Reviews 2023 Rare Neurological Disease Special Report. “We’re starting to see clinical response to some things that have been in trials – after decades of banging our heads on the wall trying new therapies, only to see them fail. I think it’s about reframing Duchenne muscular dystrophy [DMD] and facioscapulohumeral muscular dystrophy [FSHD] as treatable by target therapy because previously, they were treated with supportive care.”
DMD: Current and emerging therapies
DMD is caused by a mutation in the dystrophin gene on the X chromosome that inhibits production of dystrophin, a protein that shields muscles from injury during contraction. Dystrophin deficiency prevents muscle recovery, resulting in muscle-cell death and, ultimately, loss of function due to muscle degeneration.
FDA-approved exon-skipping therapies. Treatment modalities for what has historically been an incurable, lifespan-shortening disease involved supportive care that addresses symptoms, not the underlying cause. Consequently, many patients with DMD live only into their 20s and 30s. The tide began to turn in 2016, however, when the U.S. Food and Drug Administration granted accelerated approval for eteplirsen, an exon 51–skipping treatment that was the first RNA-based therapy for DMD to target the underlying cause. Additional exon-skipping therapies followed, including casimersen, which skips exon 45, and golodirsen and viltolarsen, which skip exon 53.
AOC 1044: Novel exon-skipping. In April 2023, the FDA granted orphan-drug designation to the experimental drug antibody oligonucleotide conjugate (AOC) 1044 that skips exon 44. A small interfering RNA (siRNA), AOC 1044 works in patients who have a mutation amenable to exon 44 skipping (a disease type known as DMD44) by delivering phosphorodiamidate morpholino to skeletal muscle and heart tissue that skips exon 44. The process allows for dystrophin production, thereby preventing degradation of muscle tissue.
The orphan drug status of AOC 1044 made it available to the population of patients enrolled in the EXPLORE44 Phase 1/2 trial. However, studies demonstrating effectiveness of the drug – with the hope of, ultimately, providing widespread access to AOC 1044 – are still underway. In one of those studies, investigators expect to enroll approximately 40 healthy volunteers and 24 DMD44 patients 7-27 years of age.3 The study will evaluate the effects of exon skipping and dystrophin protein levels in participants who have DMD44.
Delandistrogene moxeparvovec. Oct. 27, 2021, marked the inception of the phase 3 Multinational, Randomized, Double-Blind, Placebo-Controlled Systemic Gene Delivery Study to Evaluate the Safety and Efficacy of SRP-9001 in Subjects With Duchenne Muscular Dystrophy (EMBARK). The trial is evaluating the safety and efficacy of the gene-therapy agent delandistrogene moxeparvovec in ambulatory boys who were 4 to less than 8 years of age at randomization. The 126 boys enrolled in the trial met the criteria of (1) a diagnosis of DMD confirmed by documented clinical findings and previous genetic testing and (2) a pathogenic frameshift mutation stop codon located between exons 18 and 79 (inclusive), except for a mutation fully contained within exon 45.
Additional inclusion criteria were (1) the ability to cooperate with motor-assessment testing and (2) receiving a steady daily dose of oral corticosteroid for 12 weeks or longer prior to screening, and (3) the expectation of maintaining the study dosage throughout screening. Boys who had previously received gene therapy, investigational medication, or any treatment that could have amplified dystrophin expression within the time limit specified by the protocol were ineligible to participate. Boys were excluded from the study if they presented with any other illness, medical condition, or need for chronic drug treatment.
Exon-skipping therapies in trials. Various biotech and pharmaceutical companies have initiated clinical trials to explore the potential of additional exon-skipping therapies for the DMD population:
ENTR-601-44 is another exon 44–skipping therapy in the pipeline.
On Aug. 22, 2023, the FDA approved delandistrogene moxeparvovec-rokl, a recombinant gene therapy utilizing an adenovirus vector. The product is indicated for ambulatory patients with DMD 4-5 years of age who have a confirmed mutation of the dystrophin gene.
Dyne Therapeutics is actively recruiting participants to investigate Dyne 251, its exon 51–skipping therapy.
Trials are in the works by BioMarin Pharmaceutical for its next-generation peptide-conjugated phosphorodiamidate morpholino oligomers (PPMO) for skipping exon 51.
Despite the prospects of such therapy, therapeutic targeting of exon 44 addresses only patients with DMD44, who account for approximately 10% of the DMD population. Disease involving the most prevalent site of a dystrophin gene mutation, exon 51, affects 13% of the DMD population. This leaves the majority of patients with DMD without gene therapy. Yet Dr. Brandsema is optimistic nevertheless.
“We were just failing over and over again with DMD treatment, but there is some hope now,” Dr. Brandsema said. “Also, FSHD is right on the cusp of having new therapies approaching.”
FSHD: Emerging therapies
The third more common type of muscular dystrophy is not a life-threatening condition. FSHD affects approximately 4 of every 100,000 people.1 An autosomal-dominant condition, FSHD is ultimately caused by inappropriate expression of the DUX4 protein product – a consequence of a complex genetic activity involving DUX4, its chromosomal locus, and the number of repeats of a microsatellite called D4Z4.4 The disease usually starts in proximal regions of the face (that is, surrounding the eyes and mouth), before spreading to muscular groups of the limbs – most prominently, muscles of the scapulae and humeri. Symptoms usually appear in these places initially, but the condition can affect any part of the body. Fifty percent of FSHD patients experience loss of high-frequency hearing and present with retinovasculopathy. Like DMD, FSHD varies in severity, with some forms presenting at birth.
AOC 1020-CS1 is an example of a new FSHD treatment under investigation. The phase 1/2 FORTITUDE trial is a randomized, double-blind, placebo-controlled study exploring the safety, tolerability, pharmacokinetics, pharmacodynamics, and potential efficacy of single- and multiple-dose AOC 1020-CS1 therapy in FSHD.5 The trial began in April 2023; estimated completion date is September 2025.
As with many rare diseases, however, following patients and capturing data that fully narrate their story remains challenging in both DMD and FSHD. Although clinical trials undoubtedly offer hope of expanding treatment options and additional insights into disease-state management, the often insidious, complex nature of some rare diseases, such as DMD and FSHD, presents some limitations.
“Patients are hard to measure,” Dr. Brandsema explained, “because they’re so variable at baseline in history and progress in a different [slower] way than timelines are set up in our system to study drugs.”
Neonatal screening and early diagnosis: Imperative for improving outcomes
Neonatal screening helps with early detection and treatment. Prompt diagnosis does not necessarily prolong a DMD patient’s life, but it can enhance their quality of life.
DNA diagnostics. A critical component of the path to treatment is DNA diagnostics. According to Barry J. Byrne, MD, PhD, chief medical advisor of the Muscular Dystrophy Association, the Human Genome Project conducted by the National Institutes of Health helped make DNA tests affordable; such tests run about $800 today. However, given continuous advancements in sequencing, Dr. Byrne said that whole-exome sequencing for $100 is within reach.
In terms of accessibility, some nations – Canada is an example – include testing as part of national health care services. In the United States, coverage for testing varies by health insurance plan. In addition, some plans have favored rapid diagnostic testing, and the overall cost is often individualized to the patient.
Early diagnosis and supportive care. Early diagnosis can certainly help improve DMD patients’ quality of life; supportive care provides some benefit. Dr. Byrne stressed the importance of managing extraskeletal clinical manifestations in this patient population. A critical area is initiating cardiovascular treatment immediately following diagnosis, even if the patient does not exhibit cardiovascular symptoms.
“Cardiac manifestations are actually the cause of mortality in DMD, and most boys with DMD should begin cardiovascular treatment shortly after diagnosis,” Dr. Byrne told Neurology Reviews 2023 Rare Neurological Disease Special Report. “The message to neurologists is that these patients can benefit from early cardiovascular treatment because we can prevent the complications of DMD-related heart failure until much later in life.”
Historically, clinicians used echocardiography as the mainstay tool to assess cardiovascular function; however, more and more clinicians are turning to magnetic resonance imaging for such investigation. Dr. Byrne, a cardiologist, explained that magnetic resonance imaging identifies cardiovascular dysfunction at earlier stages than echocardiography can. In addition, although DMD patients frequently experience fatigue, Dr. Byrne cautions neurologists that fatigue is usually related to muscle weakness, not necessarily heart failure.
DMD therapies carry a hefty price
Right now, the projected price range of AOC 1044 is $3.2 million to $3.4 million. Akin to the case with onasemnogene abeparvovec-xioi (Zolgensma) for spinal muscular atrophy, the world’s first gene therapy and first seven-figure drug, the manufacturer of AOC 1044 based pricing on the anticipated cost of treating a DMD44 patient throughout the lifespan, according to Dr. Byrne.
Delandistrogene moxeparvovec might come with an even higher price tag. A cost-effectiveness analysis study priced the therapy at $5 million. In a presentation to investors, the manufacturer projected the price in the range of $5 million to $13 million.6,7
‘It takes a village’: Comprehensive care requires a multidisciplinary team
Dr. Brandsema and Dr. Byrne agree: Optimizing outcomes requires ongoing coordinated and collaborative efforts of an interdisciplinary team of health care providers for the duration of DMD and FSHD patients’ lifespan.
A neurologist by training, Dr. Brandsema recognizes the importance of interdisciplinary collaboration in caring for patients with DMD, given the multiorgan manifestations of the disease.
“We have some hope with DMD, and FSHD is right on the cusp of having new therapies approaching ... It is important to recognize that interdisciplinary follow-up and optimized standard of care are important after dosing.”
“I think many patients living with neurological disorders have multiple providers they rely on for care,” Dr. Byrne said, “but cardiovascular and pulmonary care are important because both are affected in the case of DMD – not so much in FSHD.”
Ultimately, advancements in therapy and care give patients living with these disorders, and their caregivers, a renewed sense of hope – hope that their life will be improved by breakthrough therapies that have been approved or will arrive soon.
Dr. Brandsema discloses he is a consultant for Alexion, Audentes, AveXis/Novartis, Biogen, Cytokinetics, Dyne, Edgewise, Fibrogen, Genentech/Roche, Janssen, Marathon, Momenta, NS Pharma, PTC Therapeutics, Sarepta, Scholar Rock, Takeda, and WaVe. He is a speaker for AveXis and Biogen, a medical advisory council member for Cure SMA, and a site investigator for clinical trials with Alexion, Astellas, AveXis/Novartis, Biogen, Catabasis, CSL Behring, Cytokinetics, Fibrogen, Genentech/Roche, Ionis, Lilly, Janssen, Pfizer, PTC Therapeutics, Sarepta, Scholar Rock, Summit, and WaVe. Dr. Byrne has no relevant financial disclosures.
References
1. Centers for Disease Control and Prevention. What is muscular dystrophy? Updated Nov. 21, 2022. Accessed Sept. 3, 2023. https://www.cdc.gov/ncbddd/musculardystrophy/facts.html.
2. FDA approves first gene therapy for treatment of certain patients with Duchenne muscular dystrophy. U.S. Food and Drug Administration. Press release. June 22, 2023. Accessed Sept. 3, 2023. https://www.fda.gov/news-events/press-announcements/fda-approves-first-gene-therapy-treatment-certain-patients-duchenne-muscular-dystrophy.
3. Study of AOC 1044 in healthy adult volunteers and participants with Duchenne muscular dystrophy (DMD) mutations amenable to exon 44 skipping (EXPLORE44). ClinicalTrials.gov Identifier: NCT05670730. Updated April 4, 2023. Accessed Sep. 3, 2023. https://www.clinicaltrials.gov/study/NCT05670730?cond=DMD&intr=AOC%201044&rank=1.
4. Statland JM, Tawil R. Facioscapulohumeral muscular dystrophy. Continuum (Minneap. Minn). 2016;22(6, Muscle and Neuromuscular Junction Disorders):1916-31. doi: 10.1212/CON.0000000000000399.
5. Phase 1/2 study of AOC 1020 in adults with facioscapulohumeral muscular dystrophy (FSHD) (FORTITUDE). ClinicalTrials.gov Identifier: NCT05747924. Updated Aug. 9, 2023. Accessed Sept. 3, 2023. https://clinicaltrials.gov/study/NCT05747924?term=fORTITUDE&cond=Facioscapulohumeral%20Muscular%20Dystrophy&rank=1.
6. Klimchak AC, Sedita LE, Rodino-Klapac LR, et al. Assessing the value of delandistrogene moxeparvovec (SRP-9001) gene therapy in patients with Duchenne muscular dystrophy in the United States. J Mark Access Health Policy. 2023;11(1):2216518. doi: 10.1080/20016689.2023.2216518.
7. Ingram D. [Investor relations presentation.] Sarepta Therapeutics website. June 22, 2023. Accessed Sept. 3, 2023. https://investorrelations.sarepta.com/static-files/7216948c-f688-4024-922e-39761bc7a984.
“There have been so many breakthroughs recently on the side of genetically targeted treatment [for muscular dystrophy] that supports muscle better,” said John F. Brandsema, MD, a child neurologist and section head at Children’s Hospital of Philadelphia, in an interview with Neurology Reviews 2023 Rare Neurological Disease Special Report. “We’re starting to see clinical response to some things that have been in trials – after decades of banging our heads on the wall trying new therapies, only to see them fail. I think it’s about reframing Duchenne muscular dystrophy [DMD] and facioscapulohumeral muscular dystrophy [FSHD] as treatable by target therapy because previously, they were treated with supportive care.”
DMD: Current and emerging therapies
DMD is caused by a mutation in the dystrophin gene on the X chromosome that inhibits production of dystrophin, a protein that shields muscles from injury during contraction. Dystrophin deficiency prevents muscle recovery, resulting in muscle-cell death and, ultimately, loss of function due to muscle degeneration.
FDA-approved exon-skipping therapies. Treatment modalities for what has historically been an incurable, lifespan-shortening disease involved supportive care that addresses symptoms, not the underlying cause. Consequently, many patients with DMD live only into their 20s and 30s. The tide began to turn in 2016, however, when the U.S. Food and Drug Administration granted accelerated approval for eteplirsen, an exon 51–skipping treatment that was the first RNA-based therapy for DMD to target the underlying cause. Additional exon-skipping therapies followed, including casimersen, which skips exon 45, and golodirsen and viltolarsen, which skip exon 53.
AOC 1044: Novel exon-skipping. In April 2023, the FDA granted orphan-drug designation to the experimental drug antibody oligonucleotide conjugate (AOC) 1044 that skips exon 44. A small interfering RNA (siRNA), AOC 1044 works in patients who have a mutation amenable to exon 44 skipping (a disease type known as DMD44) by delivering phosphorodiamidate morpholino to skeletal muscle and heart tissue that skips exon 44. The process allows for dystrophin production, thereby preventing degradation of muscle tissue.
The orphan drug status of AOC 1044 made it available to the population of patients enrolled in the EXPLORE44 Phase 1/2 trial. However, studies demonstrating effectiveness of the drug – with the hope of, ultimately, providing widespread access to AOC 1044 – are still underway. In one of those studies, investigators expect to enroll approximately 40 healthy volunteers and 24 DMD44 patients 7-27 years of age.3 The study will evaluate the effects of exon skipping and dystrophin protein levels in participants who have DMD44.
Delandistrogene moxeparvovec. Oct. 27, 2021, marked the inception of the phase 3 Multinational, Randomized, Double-Blind, Placebo-Controlled Systemic Gene Delivery Study to Evaluate the Safety and Efficacy of SRP-9001 in Subjects With Duchenne Muscular Dystrophy (EMBARK). The trial is evaluating the safety and efficacy of the gene-therapy agent delandistrogene moxeparvovec in ambulatory boys who were 4 to less than 8 years of age at randomization. The 126 boys enrolled in the trial met the criteria of (1) a diagnosis of DMD confirmed by documented clinical findings and previous genetic testing and (2) a pathogenic frameshift mutation stop codon located between exons 18 and 79 (inclusive), except for a mutation fully contained within exon 45.
Additional inclusion criteria were (1) the ability to cooperate with motor-assessment testing and (2) receiving a steady daily dose of oral corticosteroid for 12 weeks or longer prior to screening, and (3) the expectation of maintaining the study dosage throughout screening. Boys who had previously received gene therapy, investigational medication, or any treatment that could have amplified dystrophin expression within the time limit specified by the protocol were ineligible to participate. Boys were excluded from the study if they presented with any other illness, medical condition, or need for chronic drug treatment.
Exon-skipping therapies in trials. Various biotech and pharmaceutical companies have initiated clinical trials to explore the potential of additional exon-skipping therapies for the DMD population:
ENTR-601-44 is another exon 44–skipping therapy in the pipeline.
On Aug. 22, 2023, the FDA approved delandistrogene moxeparvovec-rokl, a recombinant gene therapy utilizing an adenovirus vector. The product is indicated for ambulatory patients with DMD 4-5 years of age who have a confirmed mutation of the dystrophin gene.
Dyne Therapeutics is actively recruiting participants to investigate Dyne 251, its exon 51–skipping therapy.
Trials are in the works by BioMarin Pharmaceutical for its next-generation peptide-conjugated phosphorodiamidate morpholino oligomers (PPMO) for skipping exon 51.
Despite the prospects of such therapy, therapeutic targeting of exon 44 addresses only patients with DMD44, who account for approximately 10% of the DMD population. Disease involving the most prevalent site of a dystrophin gene mutation, exon 51, affects 13% of the DMD population. This leaves the majority of patients with DMD without gene therapy. Yet Dr. Brandsema is optimistic nevertheless.
“We were just failing over and over again with DMD treatment, but there is some hope now,” Dr. Brandsema said. “Also, FSHD is right on the cusp of having new therapies approaching.”
FSHD: Emerging therapies
The third more common type of muscular dystrophy is not a life-threatening condition. FSHD affects approximately 4 of every 100,000 people.1 An autosomal-dominant condition, FSHD is ultimately caused by inappropriate expression of the DUX4 protein product – a consequence of a complex genetic activity involving DUX4, its chromosomal locus, and the number of repeats of a microsatellite called D4Z4.4 The disease usually starts in proximal regions of the face (that is, surrounding the eyes and mouth), before spreading to muscular groups of the limbs – most prominently, muscles of the scapulae and humeri. Symptoms usually appear in these places initially, but the condition can affect any part of the body. Fifty percent of FSHD patients experience loss of high-frequency hearing and present with retinovasculopathy. Like DMD, FSHD varies in severity, with some forms presenting at birth.
AOC 1020-CS1 is an example of a new FSHD treatment under investigation. The phase 1/2 FORTITUDE trial is a randomized, double-blind, placebo-controlled study exploring the safety, tolerability, pharmacokinetics, pharmacodynamics, and potential efficacy of single- and multiple-dose AOC 1020-CS1 therapy in FSHD.5 The trial began in April 2023; estimated completion date is September 2025.
As with many rare diseases, however, following patients and capturing data that fully narrate their story remains challenging in both DMD and FSHD. Although clinical trials undoubtedly offer hope of expanding treatment options and additional insights into disease-state management, the often insidious, complex nature of some rare diseases, such as DMD and FSHD, presents some limitations.
“Patients are hard to measure,” Dr. Brandsema explained, “because they’re so variable at baseline in history and progress in a different [slower] way than timelines are set up in our system to study drugs.”
Neonatal screening and early diagnosis: Imperative for improving outcomes
Neonatal screening helps with early detection and treatment. Prompt diagnosis does not necessarily prolong a DMD patient’s life, but it can enhance their quality of life.
DNA diagnostics. A critical component of the path to treatment is DNA diagnostics. According to Barry J. Byrne, MD, PhD, chief medical advisor of the Muscular Dystrophy Association, the Human Genome Project conducted by the National Institutes of Health helped make DNA tests affordable; such tests run about $800 today. However, given continuous advancements in sequencing, Dr. Byrne said that whole-exome sequencing for $100 is within reach.
In terms of accessibility, some nations – Canada is an example – include testing as part of national health care services. In the United States, coverage for testing varies by health insurance plan. In addition, some plans have favored rapid diagnostic testing, and the overall cost is often individualized to the patient.
Early diagnosis and supportive care. Early diagnosis can certainly help improve DMD patients’ quality of life; supportive care provides some benefit. Dr. Byrne stressed the importance of managing extraskeletal clinical manifestations in this patient population. A critical area is initiating cardiovascular treatment immediately following diagnosis, even if the patient does not exhibit cardiovascular symptoms.
“Cardiac manifestations are actually the cause of mortality in DMD, and most boys with DMD should begin cardiovascular treatment shortly after diagnosis,” Dr. Byrne told Neurology Reviews 2023 Rare Neurological Disease Special Report. “The message to neurologists is that these patients can benefit from early cardiovascular treatment because we can prevent the complications of DMD-related heart failure until much later in life.”
Historically, clinicians used echocardiography as the mainstay tool to assess cardiovascular function; however, more and more clinicians are turning to magnetic resonance imaging for such investigation. Dr. Byrne, a cardiologist, explained that magnetic resonance imaging identifies cardiovascular dysfunction at earlier stages than echocardiography can. In addition, although DMD patients frequently experience fatigue, Dr. Byrne cautions neurologists that fatigue is usually related to muscle weakness, not necessarily heart failure.
DMD therapies carry a hefty price
Right now, the projected price range of AOC 1044 is $3.2 million to $3.4 million. Akin to the case with onasemnogene abeparvovec-xioi (Zolgensma) for spinal muscular atrophy, the world’s first gene therapy and first seven-figure drug, the manufacturer of AOC 1044 based pricing on the anticipated cost of treating a DMD44 patient throughout the lifespan, according to Dr. Byrne.
Delandistrogene moxeparvovec might come with an even higher price tag. A cost-effectiveness analysis study priced the therapy at $5 million. In a presentation to investors, the manufacturer projected the price in the range of $5 million to $13 million.6,7
‘It takes a village’: Comprehensive care requires a multidisciplinary team
Dr. Brandsema and Dr. Byrne agree: Optimizing outcomes requires ongoing coordinated and collaborative efforts of an interdisciplinary team of health care providers for the duration of DMD and FSHD patients’ lifespan.
A neurologist by training, Dr. Brandsema recognizes the importance of interdisciplinary collaboration in caring for patients with DMD, given the multiorgan manifestations of the disease.
“We have some hope with DMD, and FSHD is right on the cusp of having new therapies approaching ... It is important to recognize that interdisciplinary follow-up and optimized standard of care are important after dosing.”
“I think many patients living with neurological disorders have multiple providers they rely on for care,” Dr. Byrne said, “but cardiovascular and pulmonary care are important because both are affected in the case of DMD – not so much in FSHD.”
Ultimately, advancements in therapy and care give patients living with these disorders, and their caregivers, a renewed sense of hope – hope that their life will be improved by breakthrough therapies that have been approved or will arrive soon.
Dr. Brandsema discloses he is a consultant for Alexion, Audentes, AveXis/Novartis, Biogen, Cytokinetics, Dyne, Edgewise, Fibrogen, Genentech/Roche, Janssen, Marathon, Momenta, NS Pharma, PTC Therapeutics, Sarepta, Scholar Rock, Takeda, and WaVe. He is a speaker for AveXis and Biogen, a medical advisory council member for Cure SMA, and a site investigator for clinical trials with Alexion, Astellas, AveXis/Novartis, Biogen, Catabasis, CSL Behring, Cytokinetics, Fibrogen, Genentech/Roche, Ionis, Lilly, Janssen, Pfizer, PTC Therapeutics, Sarepta, Scholar Rock, Summit, and WaVe. Dr. Byrne has no relevant financial disclosures.
References
1. Centers for Disease Control and Prevention. What is muscular dystrophy? Updated Nov. 21, 2022. Accessed Sept. 3, 2023. https://www.cdc.gov/ncbddd/musculardystrophy/facts.html.
2. FDA approves first gene therapy for treatment of certain patients with Duchenne muscular dystrophy. U.S. Food and Drug Administration. Press release. June 22, 2023. Accessed Sept. 3, 2023. https://www.fda.gov/news-events/press-announcements/fda-approves-first-gene-therapy-treatment-certain-patients-duchenne-muscular-dystrophy.
3. Study of AOC 1044 in healthy adult volunteers and participants with Duchenne muscular dystrophy (DMD) mutations amenable to exon 44 skipping (EXPLORE44). ClinicalTrials.gov Identifier: NCT05670730. Updated April 4, 2023. Accessed Sep. 3, 2023. https://www.clinicaltrials.gov/study/NCT05670730?cond=DMD&intr=AOC%201044&rank=1.
4. Statland JM, Tawil R. Facioscapulohumeral muscular dystrophy. Continuum (Minneap. Minn). 2016;22(6, Muscle and Neuromuscular Junction Disorders):1916-31. doi: 10.1212/CON.0000000000000399.
5. Phase 1/2 study of AOC 1020 in adults with facioscapulohumeral muscular dystrophy (FSHD) (FORTITUDE). ClinicalTrials.gov Identifier: NCT05747924. Updated Aug. 9, 2023. Accessed Sept. 3, 2023. https://clinicaltrials.gov/study/NCT05747924?term=fORTITUDE&cond=Facioscapulohumeral%20Muscular%20Dystrophy&rank=1.
6. Klimchak AC, Sedita LE, Rodino-Klapac LR, et al. Assessing the value of delandistrogene moxeparvovec (SRP-9001) gene therapy in patients with Duchenne muscular dystrophy in the United States. J Mark Access Health Policy. 2023;11(1):2216518. doi: 10.1080/20016689.2023.2216518.
7. Ingram D. [Investor relations presentation.] Sarepta Therapeutics website. June 22, 2023. Accessed Sept. 3, 2023. https://investorrelations.sarepta.com/static-files/7216948c-f688-4024-922e-39761bc7a984.
