CTLA4 and cancer: Currently approved-ICIs such as monoclonal antibodies (mAb) targeting programmed cell death protein 1 (anti-PD-1) (Nivolumab, Pembrolizumab, and Cemiplimab), anti-PD-1 ligand (anti-PD-L1) (Atezolimumab, Durvalumab and Avelumab), and cytotoxic T-lymphocyte-associated protein 4 (anti-CTLA-4) (Ipilimumab) have revolutionized cancer treatment and resulted in improved clinical outcomes for many types of cancers (3).