CTLA4 and cancer: Currently, three types of ICIs have been approved by the FDA for cancer treatment, such as programmed death-1 (PD-1) inhibitors, including pembrolizumab, nivolumab, cemiplimab; its ligand (PD-1L), including atezolizumab, avelumab, and durvalumab; ipilimumab and tremelimumab, which are cytotoxic T-lymphocyte antigen 4 (CTLA-4) inhibitors; and relatlimab, a lymphocyte activation gene-3 (LAG3) inhibitor [12,13].