Three FDA-approved immune checkpoint inhibitors (ICIs) targeting programmed cell death 1 (PD-1) and cytotoxic T lymphocyte antigen 4 (CTLA-4) (Pembrolizumab, Nivolumab, and Ipilimumab, respectively) are currently in clinical use for colorectal cancer [3]. Here, PDCD1 is linked to colorectal cancer.