August 2021: The FDA approved avapritinib (AyvakitTM, Blueprint Medicines Corp.) for adult patients with advanced systemic mastocytosis (AdvSM), which includes aggressive systemic mastocytosis (ASM), systemic mastocytosis with an associated haematological neoplasm (SM-AHN), and mast cell leukaemia (MCL).
EXPLORER (NCT02561988) and PATHFINDER (NCT03580655), two multi-center, single-arm, open-label clinical trials recruiting patients with AdvSM, were used to assess efficacy. The overall response rate (ORR) was the primary efficacy outcome measure, as determined by a central committee using modified IWG-MRT-ECNM criteria. Duration of response (DOR), time to response, and changes in individual markers of mast cell burden were also used to assess efficacy. Avapritinib was given to 53 patients in daily doses of up to 200 mg.
In both studies, the overall response rate (ORR) was 57 percent (95 percent CI: 42, 70) (n=53), with 28 percent complete remissions and 28 percent partial remissions. The median response time was 2.1 months and the median response length was 38.3 months (95 percent confidence interval: 19, not estimable).
Edema, diarrhoea, nausea, and fatigue/asthenia were the most prevalent adverse effects in patients taking AdvSM (incidence 20%).
Patients with AdvSM with platelet counts of less than 50 X 109/L should not be treated with avapritinib.
For individuals with AdvSM, the suggested avapritinib dose is 200 mg orally once daily.
Reference: https://www.fda.gov/
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