The FDA has approved avapritinib for the treatment of adult patients with advanced systemic mastocytosis (SM), SM with an associated hematologic neoplasm, and mast cell leukemia.
This decision is based on efficacy data from the EXPLORER and PATHFINDER trials. Patients in both trials (n=53) received avapritinib 200 mg daily and had a combined overall response rate of 57%, with 28% complete remissions and 28% partial remissions. Median duration of response was 38.3 months and median time to response was 2.1 months.
Adverse events occurring in ≥20% of patients with SM were edema, diarrhea, nausea, and fatigue/asthenia. The FDA does not recommend avapritinib for patients whose platelet counts are less than 50×109/L.