Inhibitor can improve symptoms of systemic mastocytosis

Photo by Jen Smith

SAN DIEGO—The KIT D816V inhibitor avapritinib can improve symptoms of systemic mastocytosis (SM), according to researchers.

Patients treated with avapritinib in a phase 1 trial had an overall response rate (ORR) of 83%, a 41% mean reduction in mastocytosis symptoms from baseline, and a 58% mean reduction in the most bothersome symptom domain.

Most adverse events (AEs) in this trial were grade 1 or 2. However, 66% of patients did have grade 3 or higher treatment-related AEs that necessitated dose reductions.

Jason R. Gotlib, MD, of Stanford University School of Medicine in California, presented these results, from the EXPLORER trial (NCT02561988), at the 2018 ASH Annual Meeting (abstract 351).

Patients and treatment

The trial enrolled 67 patients—90% with advanced SM and 10% with indolent or smoldering SM. The patients’ median age was 62 (range, 34 to 83), and 49% were female.

Patients had received a median of 3 (range, 0 to 3) prior therapies. Sixty percent of patients had received any prior therapy, and 23% had received midostaurin. Thirty-three percent were on steroid therapy at baseline.

Eighty-four percent of patients had the KIT D816V mutation, and 1% had the KIT D816Y mutation. Forty-five percent of patients had mutations in SRSF2, ASXL1, and RUNX1.

In the dose-escalation portion of the trial, patients received avapritinib at 30 mg to 400 mg once daily in continuous 28-day cycles. In the expansion portion of the trial, patients received avapritinib at 200 mg or 300 mg once daily.

Response

There were 29 patients evaluable for response. The ORR was 83% (n=24). The rate of complete response (CR) was 10% (n=3), the rate of CR with partial hematologic recovery (CRh) was 14% (n=4), and the partial response rate was 48% (n=14).

Ten percent (n=3) of patients had clinical improvement, 17% (n=5) had stable disease, and none of the patients progressed.

Among the 10 patients treated at a dose of 200 mg or lower, the ORR was 90% (n=9). The CR rate was 30% (n=3), the rate of CRh was 20% (n=2), and the partial response rate was 30% (n=3). Ten percent (n=1) of patients each had clinical improvement or stable disease.

Dr. Gotlib noted that responses have been durable and deepened over time.

At a median follow-up of 14 months, the median duration of response had not been reached. The 12-month response rate is 76%.

The median time to initial response is 2 months, and the median time to CR/CRh is 9 months.

Safety

Seventy-eight percent of patients (52/67) were still on treatment at last follow-up. Four percent (4/67) discontinued treatment due to related AEs, and 66% (44/67) had grade 3 or higher AEs that prompted dose reductions.

AEs prompting discontinuation included refractory ascites, encephalopathy, and intracranial bleeding. AEs necessitating dose reductions were largely hematologic events.

The most common AEs were periorbital edema (67%), anemia (52%), fatigue (37%), nausea (36%), diarrhea (34%), peripheral edema (34%), thrombocytopenia (31%) vomiting (28%), cognitive effects (28%), and hair color changes (25%).

The most common grade 3/4 AEs were anemia (26%), thrombocytopenia (17%), and neutropenia (10%). There were no treatment-related deaths.

Symptoms

For symptom assessment, patients completed the Advanced Systemic Mastocytosis Symptom Assessment Form (AdvSM-SAF), a patient-reported outcomes (PRO) tool that included eight symptoms:

• Abdominal pain
• Diarrhea
• Nausea
• Vomiting
• Spots
• Itching
• Flushing
• Fatigue.

Symptoms were scored on a scale of 1 to 10. Results were analyzed as a total symptom score (TSS) combining all eight items, as a gastrointestinal domain (combining nausea, vomiting, diarrhea, and abdominal pain), and as a skin domain (combining itching, flushing, and spots). Analyses were based on 7-day average scores.

Among the 32 evaluable patients, there was a 41% reduction in TSS from baseline (P=0.043). Among the 16 most symptomatic patients, there was a 46% reduction in TSS from baseline (P=0.038).

In all 32 evaluable patients, there was a 58% reduction from baseline in the score for most bothersome symptom domain (gastrointestinal or skin; P=0.0034). In the 16 most symptomatic patients, there was 63% reduction from baseline (P=0.0038).

“This is the first advanced SM-specific PRO to demonstrate significant improvements in total symptom score,” Dr. Gotlib said. “The clinical activity and initial PRO data do support further evaluation of avapritinib in both advanced and indolent disease.”

Dr. Gotlib noted that the PATHFINDER trial (NCT03580655), a study of avapritinib in advanced SM, is now enrolling. And the PIONEER trial (NCT03731260), a study of avapritinib in patients with indolent or smoldering SM, is scheduled to begin at the end of the year.

The EXPLORER trial was sponsored by Blueprint Medicines Corporation. Dr. Gotlib reported relationships with Blueprint Medicines, Celgene, Incyte, Novartis, Deciphera, Gilead, Promedior, and Kartos.

Photo by Jen Smith

SAN DIEGO—The KIT D816V inhibitor avapritinib can improve symptoms of systemic mastocytosis (SM), according to researchers.

Patients treated with avapritinib in a phase 1 trial had an overall response rate (ORR) of 83%, a 41% mean reduction in mastocytosis symptoms from baseline, and a 58% mean reduction in the most bothersome symptom domain.

Most adverse events (AEs) in this trial were grade 1 or 2. However, 66% of patients did have grade 3 or higher treatment-related AEs that necessitated dose reductions.

Jason R. Gotlib, MD, of Stanford University School of Medicine in California, presented these results, from the EXPLORER trial (NCT02561988), at the 2018 ASH Annual Meeting (abstract 351).

Patients and treatment

The trial enrolled 67 patients—90% with advanced SM and 10% with indolent or smoldering SM. The patients’ median age was 62 (range, 34 to 83), and 49% were female.

Patients had received a median of 3 (range, 0 to 3) prior therapies. Sixty percent of patients had received any prior therapy, and 23% had received midostaurin. Thirty-three percent were on steroid therapy at baseline.

Eighty-four percent of patients had the KIT D816V mutation, and 1% had the KIT D816Y mutation. Forty-five percent of patients had mutations in SRSF2, ASXL1, and RUNX1.

In the dose-escalation portion of the trial, patients received avapritinib at 30 mg to 400 mg once daily in continuous 28-day cycles. In the expansion portion of the trial, patients received avapritinib at 200 mg or 300 mg once daily.

Response

There were 29 patients evaluable for response. The ORR was 83% (n=24). The rate of complete response (CR) was 10% (n=3), the rate of CR with partial hematologic recovery (CRh) was 14% (n=4), and the partial response rate was 48% (n=14).

Ten percent (n=3) of patients had clinical improvement, 17% (n=5) had stable disease, and none of the patients progressed.

Among the 10 patients treated at a dose of 200 mg or lower, the ORR was 90% (n=9). The CR rate was 30% (n=3), the rate of CRh was 20% (n=2), and the partial response rate was 30% (n=3). Ten percent (n=1) of patients each had clinical improvement or stable disease.

Dr. Gotlib noted that responses have been durable and deepened over time.

At a median follow-up of 14 months, the median duration of response had not been reached. The 12-month response rate is 76%.

The median time to initial response is 2 months, and the median time to CR/CRh is 9 months.

Safety

Seventy-eight percent of patients (52/67) were still on treatment at last follow-up. Four percent (4/67) discontinued treatment due to related AEs, and 66% (44/67) had grade 3 or higher AEs that prompted dose reductions.

AEs prompting discontinuation included refractory ascites, encephalopathy, and intracranial bleeding. AEs necessitating dose reductions were largely hematologic events.

The most common AEs were periorbital edema (67%), anemia (52%), fatigue (37%), nausea (36%), diarrhea (34%), peripheral edema (34%), thrombocytopenia (31%) vomiting (28%), cognitive effects (28%), and hair color changes (25%).

The most common grade 3/4 AEs were anemia (26%), thrombocytopenia (17%), and neutropenia (10%). There were no treatment-related deaths.

Symptoms

For symptom assessment, patients completed the Advanced Systemic Mastocytosis Symptom Assessment Form (AdvSM-SAF), a patient-reported outcomes (PRO) tool that included eight symptoms:

• Abdominal pain
• Diarrhea
• Nausea
• Vomiting
• Spots
• Itching
• Flushing
• Fatigue.

Symptoms were scored on a scale of 1 to 10. Results were analyzed as a total symptom score (TSS) combining all eight items, as a gastrointestinal domain (combining nausea, vomiting, diarrhea, and abdominal pain), and as a skin domain (combining itching, flushing, and spots). Analyses were based on 7-day average scores.

Among the 32 evaluable patients, there was a 41% reduction in TSS from baseline (P=0.043). Among the 16 most symptomatic patients, there was a 46% reduction in TSS from baseline (P=0.038).

In all 32 evaluable patients, there was a 58% reduction from baseline in the score for most bothersome symptom domain (gastrointestinal or skin; P=0.0034). In the 16 most symptomatic patients, there was 63% reduction from baseline (P=0.0038).

“This is the first advanced SM-specific PRO to demonstrate significant improvements in total symptom score,” Dr. Gotlib said. “The clinical activity and initial PRO data do support further evaluation of avapritinib in both advanced and indolent disease.”

Dr. Gotlib noted that the PATHFINDER trial (NCT03580655), a study of avapritinib in advanced SM, is now enrolling. And the PIONEER trial (NCT03731260), a study of avapritinib in patients with indolent or smoldering SM, is scheduled to begin at the end of the year.

The EXPLORER trial was sponsored by Blueprint Medicines Corporation. Dr. Gotlib reported relationships with Blueprint Medicines, Celgene, Incyte, Novartis, Deciphera, Gilead, Promedior, and Kartos.

Photo by Jen Smith

SAN DIEGO—The KIT D816V inhibitor avapritinib can improve symptoms of systemic mastocytosis (SM), according to researchers.

Patients treated with avapritinib in a phase 1 trial had an overall response rate (ORR) of 83%, a 41% mean reduction in mastocytosis symptoms from baseline, and a 58% mean reduction in the most bothersome symptom domain.

Most adverse events (AEs) in this trial were grade 1 or 2. However, 66% of patients did have grade 3 or higher treatment-related AEs that necessitated dose reductions.

Jason R. Gotlib, MD, of Stanford University School of Medicine in California, presented these results, from the EXPLORER trial (NCT02561988), at the 2018 ASH Annual Meeting (abstract 351).

Patients and treatment

The trial enrolled 67 patients—90% with advanced SM and 10% with indolent or smoldering SM. The patients’ median age was 62 (range, 34 to 83), and 49% were female.

Patients had received a median of 3 (range, 0 to 3) prior therapies. Sixty percent of patients had received any prior therapy, and 23% had received midostaurin. Thirty-three percent were on steroid therapy at baseline.

Eighty-four percent of patients had the KIT D816V mutation, and 1% had the KIT D816Y mutation. Forty-five percent of patients had mutations in SRSF2, ASXL1, and RUNX1.

In the dose-escalation portion of the trial, patients received avapritinib at 30 mg to 400 mg once daily in continuous 28-day cycles. In the expansion portion of the trial, patients received avapritinib at 200 mg or 300 mg once daily.

Response

There were 29 patients evaluable for response. The ORR was 83% (n=24). The rate of complete response (CR) was 10% (n=3), the rate of CR with partial hematologic recovery (CRh) was 14% (n=4), and the partial response rate was 48% (n=14).

Ten percent (n=3) of patients had clinical improvement, 17% (n=5) had stable disease, and none of the patients progressed.

Among the 10 patients treated at a dose of 200 mg or lower, the ORR was 90% (n=9). The CR rate was 30% (n=3), the rate of CRh was 20% (n=2), and the partial response rate was 30% (n=3). Ten percent (n=1) of patients each had clinical improvement or stable disease.

Dr. Gotlib noted that responses have been durable and deepened over time.

At a median follow-up of 14 months, the median duration of response had not been reached. The 12-month response rate is 76%.

The median time to initial response is 2 months, and the median time to CR/CRh is 9 months.

Safety

Seventy-eight percent of patients (52/67) were still on treatment at last follow-up. Four percent (4/67) discontinued treatment due to related AEs, and 66% (44/67) had grade 3 or higher AEs that prompted dose reductions.

AEs prompting discontinuation included refractory ascites, encephalopathy, and intracranial bleeding. AEs necessitating dose reductions were largely hematologic events.

The most common AEs were periorbital edema (67%), anemia (52%), fatigue (37%), nausea (36%), diarrhea (34%), peripheral edema (34%), thrombocytopenia (31%) vomiting (28%), cognitive effects (28%), and hair color changes (25%).

The most common grade 3/4 AEs were anemia (26%), thrombocytopenia (17%), and neutropenia (10%). There were no treatment-related deaths.

Symptoms

For symptom assessment, patients completed the Advanced Systemic Mastocytosis Symptom Assessment Form (AdvSM-SAF), a patient-reported outcomes (PRO) tool that included eight symptoms:

• Abdominal pain
• Diarrhea
• Nausea
• Vomiting
• Spots
• Itching
• Flushing
• Fatigue.

Symptoms were scored on a scale of 1 to 10. Results were analyzed as a total symptom score (TSS) combining all eight items, as a gastrointestinal domain (combining nausea, vomiting, diarrhea, and abdominal pain), and as a skin domain (combining itching, flushing, and spots). Analyses were based on 7-day average scores.

Among the 32 evaluable patients, there was a 41% reduction in TSS from baseline (P=0.043). Among the 16 most symptomatic patients, there was a 46% reduction in TSS from baseline (P=0.038).

In all 32 evaluable patients, there was a 58% reduction from baseline in the score for most bothersome symptom domain (gastrointestinal or skin; P=0.0034). In the 16 most symptomatic patients, there was 63% reduction from baseline (P=0.0038).

“This is the first advanced SM-specific PRO to demonstrate significant improvements in total symptom score,” Dr. Gotlib said. “The clinical activity and initial PRO data do support further evaluation of avapritinib in both advanced and indolent disease.”

Dr. Gotlib noted that the PATHFINDER trial (NCT03580655), a study of avapritinib in advanced SM, is now enrolling. And the PIONEER trial (NCT03731260), a study of avapritinib in patients with indolent or smoldering SM, is scheduled to begin at the end of the year.

The EXPLORER trial was sponsored by Blueprint Medicines Corporation. Dr. Gotlib reported relationships with Blueprint Medicines, Celgene, Incyte, Novartis, Deciphera, Gilead, Promedior, and Kartos.