The PD-1 inhibitor nivolumab also received FDA approval as single-agent therapy for the treatment of patients with MSI-H or dMMR CRC that has progressed following treatment with a fluoropyrimidine, oxaliplatin, and irinotecan, or in combination with ipilimumab (an anti-cytotoxic T-lymphocyte antigen 4 [CTLA-4] antibody) as first-line therapy in patients with unresectable or metastatic MSI-H or dMMR CRC based on the CheckMate-142 (NCT02060188) and CheckMate-8HW (NCT04008030) studies, respectively [179,180]. This evidence concerns the gene CTLA4 and colorectal carcinoma.