CTLA4 and cancer: Various ICIs have been approved for the treatment of numerous cancers, including anti-programmed death receptor 1 (PD-1) antibodies (Nivolumab, Pembrolizumab, and Cemiplimab), anti-programmed cell death ligand (PDL-1) antibodies (Atezolimumab, Durvalumab, and Avelumab), and anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) antibodies (Ipilimumab and Tremelimumab) [19].