ICIs which have shown to be effective in many types of cancer (anti-PD-1 mAb (pembrolizumab and nivolumab), anti-PD-L1 Ab (avelumab, durvalumab, and atezolizumab), and anti-CTLA-4 Ab (tremelimumab and ipilimumab)), are not equally effective in treating CRC [111]. Here, PDCD1 is linked to cancer.