We conducted a single‐arm phase 2 study of Cy/GVAX in combination with the anti‐PD1 therapy pembrolizumab in patients with MMR‐p metastatic CRC, to test the hypothesis that Cy/GVAX, through its effects on the colon cancer TME, may modify an otherwise PD‐1 inhibitor insensitive cancer into a sensitive one. Here, PDCD1 is linked to colorectal carcinoma.