PDCD1 and melanoma: Until now, PD-1 inhibitors (nivolumab and pembrolizumab) and PD-L1 inhibitors (atezolizumab, avelumab, and durvalumab) have been approved by the US Food and Drug Administration (FDA) for the treatment of a wide spectrum of tumors, including NSCLC, urothelial cancer, melanoma, head and neck squamous cell cancer, and lymphoma (1).