Pioneer: A Randomized, Double-Blind, Placebo-Controlled, Phase 2 Study of Avapritinib in Patients with Indolent or Smoldering Systemic Mastocytosis with Symptoms Inadequately Controlled with Standard Therapy

Background: The gain-of function mutation KIT D816V plays a central role in the pathogenesis of systemic mastocytosis (SM). Among subtypes of SM, indolent SM (ISM) is the most frequent and is associated with normal/near-normal life expectancy; smoldering SM (SSM) is a subtype with a relatively higher burden of mast cells and may be associated with an increased risk of progression to advanced mastocytosis. However, both ISM and SSM patients may experience severe symptoms associated with mast cell mediator release, such as pruritus, diarrhea, anaphylaxis, and bone pain, which can be severely debilitating and have a profoundly negative impact on quality of life. Symptomatic treatments (eg, ant…