Avapritinib granted FDA priority review of sNDA for the treatment of indolent SM

On January 23, 2022, the U.S. Food and Drug Administration (FDA) accepted a priority review to the supplemental new drug application for avapritinib, intended for the treatment of adults with indolent systemic mastocytosis (SM).¹ The FDA previously approved avapritinib for the treatment of adults with advanced SM in June 2021; however, there are currently no therapies available for the treatment of non-advanced SM.¹

This application was supported by results from the phase II PIONEER trial (NCT03731260) investigating the safety and efficacy of avapritinib versus placebo in patients with indolent SM.¹ Avapritinib produced a significant reduction in total symptom score and serum tryptase versus placebo (Table 1).¹

Table 1. Total symptom score and serum tryptase levels in patients treated with avapritinib and placebo*

TSS, total symptom score. *Adapted from Ryan.1
Outcome	Avapritinib (n = 141)	Placebo (n = 71)	p value
Mean reduction of TSS	15.6	9.2	0.003
50% reduction in serum tryptase, %	53.9	0.0	<0.0001

In terms of safety, patients treated with avapritinib experienced lower rates of adverse events, including those deemed to be serious and cognitive (Table 2).¹

Table 2. Safety outcomes for patients treated with avapritinib and placebo*

AE, adverse event. *Adapted from Ryan.1
Safety outcome, %	Avapritinib (n = 141)	Placebo (n = 71)
AEs	90.8	93.0
Serious AEs	5.0	11.3
Cognitive AEs	2.8	4.2
Treatment discontinuation due to treatment-related AEs	0.7	0.0