Diarrhea and colitis are more frequent and severe with anti-CTLA4 agents (all grades: 30%; grade 3–4: 10–16%) than with agents targeting the PD-1/PD-L1 axis (all grades: 11–16%; grade 3–4: 1–2%) [6, 7, 10, 11]. This evidence concerns the gene CTLA4 and colitis.