CTLA4 and cancer: By the end of 2022, at least seven types of ICIs, including PD-1 inhibitors (Nivolumab, Cemiplimab, Pembrolizumab), PD-L1 inhibitors (Avelumab, Durvalumab, and Atezolizumab) and CTLA-4 inhibitor (Ipilimumab) have been approved by food and drug administration (FDA) for the various cancer therapies [12].