Phase 1b consists of combined dose escalation phase and dose expansion phase. Phase 3 study will compare efficacy and safety of IBI351 combined with cetuximab versus chemotherapy in treatment of KRAS G12C-mutated metastatic colorectal cancer

A Phase 1b study of the safety, tolerability and preliminary efficacy of IBI351 combined with cetuximab in the treatment of KRAS G12C mutant metastatic colorectal cancer will be conducted based on recommended dose of IBI351, which consists of combined dose escalation phase and dose expansion phase. After confirming the efficacy and safety of IBI351 combined with cetuximab in Phase Ib, an open-label Phase 3 study of the efficacy and safety of IBI351 combined with cetuximab versus oxaliplatin-based mFOLFOX6 regimen or irinotecan-based FOLFIRI with or without bevacizumab in treatment of KRAS G12C-mutated metastatic colorectal cancer will be conducted.

Inclusion Criteria:

1. male or female subjects, ≥ 18 years and ≤ 75 years
2. have documentation of KRAS G12C mutation
3. at least one measurable lesion per RECISTv1.1
4. Eastern Cooperative Oncology Group (ECOG) Performance Status of 0-1.
5. life expectancy of >12 weeks, in the opinion of the investigator

Exclusion Criteria:

1. history of deep venous thrombosis or any other serious thromboembolism within 3 months prior to enrollment..
2. history of radiation-induced pneumonitis, idiopathic pneumonia, active pneumonia, pulmonary fibrosis, diffuse pulmonary interstitial disease, or organizing pneumonia.
3. surgical procedures (excluding needle biopsy) performed within 28 days prior to enrollment that may affect the dosing or study assessments in this study.
4. received therapeutic or palliative radiation therapy within 14 days prior to enrollment
5. pregnant or lactating women