Use of Immune Checkpoint Inhibitors in Patients With Pre-established Inflammatory Bowel Diseases: Retrospective Case Series.

The etiology of inflammatory bowel disease (IBD) has yet to be fully understood; however, it is thought to be a result of genetic, immunologic, and environmental factors, including changes in the gut microbiome.1,2 Immune checkpoint inhibitors (ICI) have revolutionized treatment of advanced cancer. They activate the immune system by promoting cytotoxic T-cell survival and antitumor effects. A total of 7 ICIs currently are approved by the United States Food and Drug Administration, and target cytotoxic T lymphocyte-associated protein 4 (ipilimumab); anti-programmed cell death 1 (PD-1) (nivolumab, pembrolizumab, and cemiplimab), or anti-PD-ligand 1 (atezolizumab, durvalumab, and avelumab). However, by activating the immune system, these medications also can lead to off-target inflammation and autoimmunity, including ICI-induced colitis, which has been reported in up to 13.6% of patients.3.