The purpose of this Phase 1/2 master protocol study is to evaluate if DCC-3009 is safe, tolerable and works effectively in the treatment of GIST. The study will use a modular approach with each module being defined according to therapy: DCC-3009 alone or DCC-3009 in combination with other anticancer therapies. Each module will be conducted in 2 parts: Part 1 (Dose Escalation) and Part 2 (Dose Expansion). Participants will be treated in 28-day treatment cycles with an estimated duration of up to 2 years.