Five single-arm trials (phase Ib KEYNOTE 012 and 028, and phase II KEYNOTE 016, 164, and 158) investigated the anti-PD-1 agent pembrolizumab across different tumor types, including 149 patients with previously-treated advanced CRC, 59 of whom presented MSS/pMMR tumors. This evidence concerns the gene PDCD1 and colorectal carcinoma.