PDCD1 and melanoma: In clinical trials, both anti-cytotoxic T lymphocyte-associated protein 4 (CTLA-4; e.g., ipilimumab) and anti-programed cell death-1 (PD-1) agents (e.g., nivolumab, pembrolizumab) have demonstrated improved overall survival, PFS and ORR in patients with advanced melanoma compared with chemotherapy [6–11].