Pembrolizumab is the first PD-1 inhibitor approved by the FDA for the treatment of advanced or unresectable melanoma, which does not respond to other drugs.203 Pembrolizumab is a highly selective humanized IgG4-κ anti-PD-1 monoclonal antibody, which activates tumor infiltrating lymphocytes (TIL). The gene discussed is PDCD1; the disease is neoplasm.