Researchers have confirmed the superior overall survival, duration of treatment, and reduced serum tryptase levels of avapritinib vs best available therapy in patients with advanced systemic mastocytosis (SM) and published their results in Leukemia.

They noted that given the lack of randomized controlled trials comparing avapritinib with the best available therapy, these data provide useful insights on these treatments to patients and clinicians.

“Comparing the efficacy of avapritinib with that of existing therapies for [advanced SM] is essential to inform clinical decision making,” they said. “To address this need, the current study compared the efficacy of avapritinib to a real-world cohort of similar patients receiving [best available therapy] for [advanced SM].”

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The research team conducted a multicenter, observational, retrospective chart review to collect data on the use of the best available therapy in patients with advanced SM. These data were compared with those collected as of April 20, 2021, from the phase 1 EXPLORER and phase 2 PATHFINDER trials employing avapritinib for patients with advanced SM.

In the EXPLORER trial, patients received escalating daily doses of avapritinib and in PATHFINDER, all but 2 patients took 200 mg per day. The primary endpoint was overall survival, and secondary endpoints were the duration of treatment and serum tryptase levels. Adverse events that led to hospitalization, treatment modification, or discontinuation of the therapy were recorded only for the best available therapy cohort, given comparable data were not available in the clinical trials.

After adjusting for confounders and prognostic indicators, treatment with avapritinib was associated with significantly better overall survival compared with the best available therapy. In particular, patients treated with 200 mg or less avapritinib had a 66% lower risk of death than patients undergoing the best available therapy.

Patients on avapritinib also had a greater reduction in mast cell burden and significantly reduced serum tryptase levels compared with the best available therapy. The authors conclude the data represent a valuable perspective on the differences between the best available therapy and avapritinib in a real-world setting among patients with advanced SM.

Reference

Reiter A, Gotlib J, Álvarez-Twose I, et al. Efficacy of avapritinib versus best available therapy in the treatment of advanced systemic mastocytosis. Leukemia. Published online July 5, 2022. doi:10.1038/s41735-022-01615-z