Severe Inflammatory Colitis Related to Encorafenib and Binimetinib following Immune Checkpoint Inhibitor Therapy

Encorafenib, a BRAF kinase inhibitor, in combination with binimetinib, a selective MEK inhibitor have known gastrointestinal adverse events; however, adverse colitis events have not been well studied. We report a case series of 4 patients with melanoma who developed inflammatory colitis after BRAF and MEK inhibition with encorafenib and binimetinib, respectively. In the setting of immune checkpoint inhibitor use, BRAF and MEK inhibitors can cause significant inflammatory colitis with endoscopic patterns of predominant right colon ulcerations. It can lead to significant morbidity and frequent interruption of cancer treatment. Early recognition and prompt intervention are critical to improving patient outcomes.