CTLA4 and cancer: To date, the US Food and Drug Administration has approved the use of PD-1/PD-L1 and CTLA-4 targeted therapies for the treatment of more than 15 cancers including melanoma, non-small cell lung cancer (NSCLC), small cell lung cancer, squamous cell carcinoma of the head and neck, renal cell carcinoma (RCC), hepatocellular carcinoma (HCC), classical Hodgkin lymphoma, urothelial carcinoma, colorectal cancer (CRC) and other cancer types[3–5].