This study is to evaluate the safety and tolerability of RMC-9805 as monotherapy and in combination with RMC-6236 in adults with KRAS G12D-mutant solid tumors.

This is an open-label, multicenter, Phase 1/1b study of RMC-9805, a selective and orally bioavailable KRAS G12D(ON) inhibitor, in subjects with KRASG12D-mutant solid tumors to evaluate the safety, tolerability, pharmacokinetics (PK), and preliminary clinical activity. The study consists of two arms: RMC-9805 monotherapy arm and RMC-9805 plus RMC-6236 combination arm. Both arms consist of two parts: Part 1- dose exploration and Part 2- dose expansion.

Inclusion Criteria:

• Pathologically documented, locally advanced or metastatic solid tumor with a KRAS G12D-mutation
• Received and progressed or been intolerant to prior standard therapy (including targeted therapy) appropriate for tumor type and stage
• ECOG performance status 0 or 1
• Adequate organ function

Exclusion Criteria:

• Primary central nervous system (CNS) tumors
• Known or suspected leptomeningeal or active brain metastases or spinal cord compression
• Known or suspected impairment of gastrointestinal function that may prohibit ability to swallow or absorb an oral medication
• Participant was previously treated with an investigational KRAS G12D inhibitor, pan- or multi-RAS inhibitor, or had prior therapy with any direct RAS-targeted therapy (eg, degraders and inhibitors)

Other inclusion/exclusion criteria may apply.