PDCD1 and melanoma: Programmed death 1 (PD-1): Programmed death ligand 1 (PD-L1) immune checkpoint blockade has been demonstrated to be efficacious in a number of cancer types, including melanoma, renal cell carcinoma, bladder cancer, hematologic malignancies and non-small cell lung cancer (NSCLC)1, 2, 3 and anti-PD-1 antibodies have recently been approved for use in the United States and Asia.