Anti-PD-1 antibodies pembrolizumab, nivolumab, and cemiplimab are approved for melanoma, lung, renal cell, and head and neck cancers, and anti-PD-L1 antibodies atelizumab, avelumab, durvalumab are approved against lung, Merkel cell carcinoma (MCC), and urothelial cancers [282]. Here, PDCD1 is linked to Merkel cell skin cancer.