CTLA4 and cancer: CTLA-4 blockade has been the most successful in metastatic melanoma, while responses in other cancers such as non-small cell lung (NSCLC) (2, 3), Hodgkin’s lymphoma (4), Merkel-cell carcinoma (5), triple-negative breast cancer (6), renal cell carcinoma (7), urothelial bladder (8, 9) and squamous cell carcinoma of the head and neck (10) are common with anti-PD-1/PD-L1 therapy.