Mirdametinib + BGB-3245 in Advanced Solid Tumors

The study will be conducted in two sequential parts: Part 1 dose escalation (Phase 1) and Part 2 dose expansion (Phase 2a). Participants will receive mirdametinib and brimarafenib administered by mouth every day on a continuous schedule. Mirdametinib will be dosed twice a day (BID) and brimarafenib will be dosed once a day (QD). One treatment cycle will be 28 days. Part 1 of the study will assess the safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PDx), and preliminary evidence of anti-tumor efficacy. Part 1 will also identify the MTD and the RP2D for the combination of mirdametinib with brimarafenib. Part 2 will confirm the safety, tolerability, efficacy, PK, and PDx for the combination of mirdametinib and brimarafenib. It will follow a parallel design and include one or more dose expansion cohorts, where each participant would be treated with the combination of mirdametinib and brimarafenib at the RP2D. It will begin after the RP2D for the combination of mirdametinib and brimarafenib is identified in Part 1. Part 2 may start either in parallel with, or after, the conduct and analysis of the PDx Expansion Cohort in Part 1. Participants who experience a TEAE requiring treatment modification will be managed according to the applicable guidelines in the protocol.