Inclusion Criteria:  Locally confirmed microsatellite instability-high/ deficient mismatch repair (MSI-H/dMMR) stage IV colorectal carcinoma Locally confirmed BRAF V600E mutation in tumor tissue or blood Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 Have not received prior systemic regimens for metastatic disease. Measurable disease per RECIST 1.1 Adequate organ function  Exclusion Criteria:  Colorectal adenocarcinoma that is RAS mutant or for which RAS mutation status is unknown Known active central nervous system metastases and/or carcinomatous meningitis; leptomeningeal disease Immunodeficiency or active autoimmune disease requiring systemic treatment in the past 2 years Presence of acute or chronic pancreatitis Clinically significant cardiovascular diseases (eg, thromboembolic or cerebrovascular accident events ≤ 12 wks prior) Received a live or live-attenuated vaccine within 30 days of planned start of study medication Previous treatment with any selective BRAF inhibitor (eg, encorafenib, dabrafenib, vemurafenib, XL281/BMS-908662) or any epidermal growth factor receptor (EGFR) inhibitor (eg, cetuximab, panitumumab). Previous treatment with an immune checkpoint inhibitor (eg, anti-programmed cell death [PD-1], anti-PD-L1 or anti-PD-L2 agent); or with an agent directed to another stimulatory or co-inhibitory T-cell receptor (eg, CTLA-4, OX 40, CD137).