The most frequently used monoclonal antibodies for colorectal cancer are pembrolizumab and nivolumab, which target the programmed cell death protein 1 (PD-1) receptor, avelumab, and durvalumab, which target programmed cell death protein-ligand 1 (PD-L1), and ipilimumab, which targets cytotoxic T lymphocyte-associated protein 4 (CTLA-4). Here, CTLA4 is linked to colorectal cancer.