On December 25, 2017, pembrolizumab (Keytruda®, Merck), a highly selective, humanized monoclonal IgG4κ isotype antibody against programmed death 1 (PD-1) that selectively inhibits the interaction between PD-1 (which is expressed on activated T cells) and PD-1 ligand 1 (PD-L1) and 2 (PD-L2) [which are expressed on antigen-presenting cells (APC) and cancer cells] was approved as a second-line treatment for use after platina-based chemotherapy for patients with metastatic UC in Japan. This evidence concerns the gene PDCD1LG2 and cancer.