Immune checkpoint inhibitors targeting PD-1 (pembrolizumab and nivolumab), PD-L1 (atezolizumab and durvalumab) or CTLA-4 (tremelimumab and ipilimumab) have been granted FDA approval for metastatic CRC patients with chemorefractory dMMR-MSI-H, which represent just an ∼5% among all metastatic cases (25,82,83). Here, CTLA4 is linked to colorectal carcinoma.