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Infliximab, a monoclonal antibody against tumour necrosis factor alpha (TNF-alpha), is highly effective in achieving both clinical and endoscopic remission in paediatric inflammatory bowel disease (PIBD). 1 Current ECCO-ESPGHAN guidelines recommend intravenous induction dosing of 5mg/kg at week 0, 2 and 6 with 8 weekly maintenance dosing thereafter.1 Pro-active therapeutic drug monitoring is recommended; as adequate trough infliximab levels during induction have been proven to predict clinical remission.1 2 However, younger paediatric patients are at particular risk of under-dosing due to decreased drug exposure with lower body weight.3 Up to 50% patients develop secondary loss of response (LOR) at one year; therefore requiring dose escalation or change in biologic therapy.1 4 Studies have shown early dose optimization can reduce this secondary LOR and improve remission rates by way of preventing low trough levels and subsequent anti-drug antibodies (ADA).4The aim of this study was to review infliximab induction dosing regimens for PIBD patients. Specifically, to quantify the number of patients starting on 5mg/kg dosing that needed dose and/or frequency escalation. The hypothesis was that the majority of patients starting on lower dose induction would need dose intensification.A retrospective review of PIBD patients currently receiving infliximab in a single tertiary centre identified 120 patients receiving induction between 2013 and 2025. Data were collected and analysed on epidemiology, diagnosis, severity of disease, initial dosing and need for subsequent dose and/or frequency escalation. Post induction (pre-3rd or 4th infusion) trough infliximab levels were compared to recommended targets (>15 and 5 mg/L respectively) as per ECCO-ESPGHAN guidelines.178/120 (65%) were male and 42/120 (35%) female; with age of diagnosis between 2 and 15 years. 102/120 (85%) had Crohn’s disease, 16/120 (13%) ulcerative colitis and 2/120 (2%) had IBD-unclassified. 88/120 (73%) started on 5mg/kg induction dosing; 78/88 (89%) of these patients required either dose or frequency escalation. 58/88 (66%) needed escalation to 10mg/kg as well as escalation to 4 or 6-weekly. 13/32 (41%) patients starting on 10mg/kg needed frequency escalation. Indications for initial 10mg/kg dosing were early onset (diagnosis younger than 6 years) disease (5), fistulating (35), stricturing (3) or severe disease (8). In the 5mg/kg cohort, 9/10 (90%) early onset patients and 31/35 (89%) patients with fistulating disease needed escalation. Similarly, in the 10mg/kg cohort, 4/5 (80%) early onset patients and 6/18 (33%) patients with fistulating disease needed escalation. In the 5mg/kg cohort; 51/77 (66%) patients with available post-induction infliximab had below target levels. In the 10mg/kg cohort; 10/23 (43%) patients with available levels were below target.Infliximab is a highly effective therapy in PIBD but adequate induction dosing is essential in attaining therapeutic drug levels and therefore early clinical remission.2 This study goes someway to support the need for dose optimisation during induction; particularly in those with early onset and/or fistulating/stricturing disease. Of note, many (41%) patients who started on higher dosing still needed further optimisation. This suggests the need for starting infliximab induction with 10mg/kg dosing (rather than 5mg/kg) with pro-active post-induction therapeutic drug monitoring.References van Rheenen PF, Aloi M, Assa A, et al. The medical management of paediatric crohn’s disease: an ECCO-ESPGHAN guideline update. J Crohn’s Colitis 2021 Feb;15(2):171–194. https://doi.org/10.1093/ecco-jcc/jjaa161Kantasiripitak W, Wicha S G, Thomas D, et al. A model-based tool for guiding infliximab induction dosing to maximize long-term deep remission in children with inflammatory bowel diseases. J Crohn’s Colitis 2023 Jun;17(6):896–908. https://doi.org/10.1093/ecco-jcc/jjad009Jongsma MME, Winter DA, Huynh HQ, et al. Paediatric IBD porto group of ESPGHAN. Infliximab in young paediatric IBD patients: it is all about the dosing. Eur J Pediatr 2020 Dec;179(12):1935–1944. doi: 10.1007/s00431-020-03750-0. Epub 2020 Aug 19. PMID: 32813123; PMCID: PMC7666662.Dubinsky MC, Mendiolaza ML, Phan BL, et al. Dashboard-driven accelerated infliximab induction dosing increases infliximab durability and reduces immunogenicity. Inflammatory Bowel Dis 2022 Sep;28(9):1375–1385. https://doi.org/10.1093/ibd/izab285