PDCD1 and metastatic melanoma: The FDA has approved the combination of nivolumab (PD-1 inhibitor) and ipilimumab (CTLA-4 inhibitor) for the treatment of BRAF V600 wild-type unresectable or metastatic melanoma, metastatic RCC, colorectal cancer with MSI-H/dMMR, unresectable HCC, advanced NSCLC, unresectable malignant pleural mesothelioma, and advanced or metastatic ESCC.