CTLA4 and cancer: Immune-checkpoint inhibitors (ICIs) targeting cytotoxic T-lymphocyte-associated protein-4 (CTLA-4; ipilimumab and tremelimumab), programmed-death receptor-1 (PD-1; nivolumab, pembrolizumab and cemiplimab) or its ligand, PD-L1 (atezolizumab, durvalumab and avelumab), have been approved for the treatment of a variety of malignancies [1,2,3,4,5,6,7,8,9,10].