Nivolumab (Opdivo) is a humanized monoclonal antibody that is approved by the U.S. Food and Drug Administration for the trea™ent of patients with unresectable or metastatic melanoma. Nivolumab binds to the human cell surface receptor PD-1 (Programmed Cell Death Protein 1) and blocks its interaction with PD-L1, resulting in the activation of T-cell-mediated immune responses against tumor cells.