CTLA4 and melanoma: Ipilimumab, an example of a CTLA-4 inhibitor, has been approved by the FDA since 2011 to be used in malignant melanoma [13], with approvals for multiple other malignancies having followed, such as renal cell carcinoma (RCC), non-small cell lung cancer (NSCLC), head and neck squamous cell carcinoma, urothelial carcinoma, lymphoma, hepatocellular carcinoma, and all microsatellite instability-high tumors and others.