CTLA4 and cancer: ICIs, also known as immune checkpoint blockade therapy, targeting cytotoxic T-lymphocyte associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1), and programmed death-ligand 1 (PD-L1) prevent these receptors and ligands from binding, thereby disrupting signaling that T cells can recognize and attack cancer cells [4].