A Study of Avapritinib in Pediatric Patients With Solid Tumors Dependent on KIT or PDGFRA Signaling

This is a Phase 1/2, multicenter, open-label trial of avapritinib in participants 2 to \< 18 years of age with advanced relapsed/refractory (R/R) solid tumors, including central nervous system (CNS) tumors, that harbor a PDGFRA and/or KIT mutation (including non-synonymous point mutations, insertions, and deletions) or amplification, or DMG-H3K27a who have no available curative treatment options. This is a single-arm trial in which all participants will receive avapritinib. The study consists of 2 parts: dose confirmation, safety, and PK (Part 1) and initial efficacy, safety, and PK at the Part 2 recommended dose (Part 2).