CTLA4 and cancer: The FDA has approved various ICIs for cancer therapy [25], including PD-1 receptor inhibitors (e.g., cemiplimab, nivolumab, and pembrolizumab), PD-L1 inhibitors (e.g., atezolizumab, avelumab, and durvalumab), and CTLA-4 inhibitors (ipilimumab and tremelimumab).