The goal of this clinical trial is to evaluate FMC-376 in participants with advanced solid tumors with KRAS G12C mutations. This clinical trial will be conducted in 3 parts: Phase 1A (Dose Escalation), Phase 1B (Dose Expansion), and Phase 2 (Cohort Expansion). Multiple dose levels in participants with advanced solid tumors will be evaluated.

Inclusion Criteria:

• Histologically or cytologically confirmed locally advanced unresectable or metastatic solid tumors with KRAS G12C mutation
• Received and progressed or been intolerant to prior standard therapy OR standard therapy is considered inappropriate OR an investigational agent is considered standard of care
• Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1
• Adequate hematological, renal, and hepatic function
• Agrees not to participate in another interventional study while receiving study drug

Exclusion Criteria:

• Leptomeningeal disease or carcinomatous meningitis
• Clinically significant toxicity resulting from prior cancer therapies
• Known or suspected hypersensitivity to FMC-376 or any components of the study drug
• Condition that would interfere with study drug absorption
• Any illness or medical history that would impact safety or compliance with study requirements or impact ability to interpret study data