Nivolumab, an IgG4 mAb against PD-1, was approved following the pivotal trial CheckMate-037, on December 22, 2014, for the treatment of patients with unresectable of metastatic melanoma who have experienced disease progression following ipilimumab and, if BRAFV600 mutation-positive, a BRAF inhibitor. This evidence concerns the gene PDCD1 and metastatic melanoma.