Background and aimsPatients with very early-onset inflammatory bowel disease (VEO-IBD), with an age of onset MethodsThis retrospective study involved 30 sites worldwide. Demographic, clinical, and laboratory data were collected from patients with VEO-IBD who commenced adalimumab therapy before the age of 6 years.ResultsSeventy-eight patients (37 Crohn's disease, 26 ulcerative colitis, and 15 with IBD-unclassified) were included. Median age of IBD onset was 2.6 (1.3-4.1) years, with 30 (38.5%) patients diagnosed at age <2 years. Median age at adalimumab initiation was 4.2 (2.8-5.1) years. Adalimumab was used as second-line biologic therapy in 45 (57.7%) patients after infliximab. The median time to last follow-up was 63 (22-124) weeks. Significant improvement in clinical scores, CRP, fecal calprotectin, and weight Z-score were observed by Week 52. Adalimumab durability rates were 61.9%, 48.1%, and 35.6% after 1, 2, and 3 years, respectively. Drug discontinuation rates were not dependent on IBD type, age, prior anti-TNF exposure, or concomitant immunomodulatory treatment. Four (5.1%) patients developed serious infections, including 1 patient with TTC7A deficiency who died following adenovirus sepsis.ConclusionAdalimumab therapy is a viable therapeutic option in patients with VEO-IBD with an acceptable safety profile.