Anti-PD-1 antibodies such as pembrolizumab and nivolumab contribute remarkably to treating different cancers including metastatic melanoma, non-small cell lung carcinoma, renal cell carcinoma, urothelial carcinoma, Hodgkin’s lymphoma, microsatellite instability-high (MSI-H) or mismatch repair-deficient solid tumors, and head and neck carcinoma [18,19,20,21]. Here, PDCD1 is linked to cancer.