Subcutaneous infliximab as a maintenance option in pediatric IBD: a real-world cohort including younger and lower-weight children

BACKGROUND: Subcutaneous infliximab (SC-IFX) offers an alternative to intravenous infliximab (IV-IFX) in adults with inflammatory bowel disease (IBD), but evidence in children is scarce. This study reports treatment persistence, tolerability, and pharmacokinetics in a real-world pediatric IBD cohort following transition from IV-IFX. METHODS: We conducted a single center retrospective study including all pediatric IBD patients transitioned from IV-IFX to SC-IFX (120 mg every other week) at our institution between November 2023 and April 2025. Clinical disease activity scores, inflammatory markers, IFX serum concentrations, and anti-IFX antibodies (AIA) were assessed at baseline and during follow-up. The primary outcome was treatment persistence. Secondary outcomes included disease activity, pharmacokinetics, immunogenicity and tolerability. RESULTS: Twenty patients (median age 14.5 years; range 5-17), including six children < 12 years and five weighing < 40 kg, were included. After a median observation period of 44 weeks (IQR 26-60), 16/20 patients (80%) remained on SC-IFX, with no significant difference between Crohn's disease and ulcerative colitis. In a subgroup of four patients who received SC-IFX as a third dose following two intravenous induction doses, 3/4 (75%) maintained treatment over a median observation period of 60 weeks (range 16-64 weeks) and remained in clinical remission during follow-up. IFX serum concentrations increased after switching (median 11.8 µg/mL pre-switch vs. ≥24 µg/mL at follow-up), with most follow-up measurements reaching the assay ceiling. Concentrations were descriptively comparable between weight groups. All patients with detectable AIA prior to switching became antibody-negative during SC-IFX therapy, and no de novo antibodies were observed. Two patients discontinued therapy due to worsening of pre-existing paradoxical psoriasis. No other adverse events were documented. CONCLUSIONS: SC-IFX showed high persistence, stable inflammatory markers and good tolerability in this pediatric cohort, including younger and lower-weight children. SC-IFX appears to be a feasible maintenance option in selected pediatric patients, including early use after induction. Prospective studies are warranted to define pediatric-specific pharmacokinetic targets and individualized dosing strategies.