PD‐1 blockade (aPD‐1) is thought to operate by restoring immunosuppressed CD8+ TIL effector functions and enhancing their cytotoxic activity against tumor cells by blocking the binding of PD‐1 to its ligands.5, 6, 25 Preclinical murine studies have corroborated this, with aPD‐1 observed to augment antitumor responses and delay metastasis in models of melanoma, colorectal and pancreatic cancer.5 This evidence concerns the gene PDCD1 and melanoma.