Proactive therapeutic drug monitoring of infliximab leads to treatment durability in paediatric Crohn's disease: A single‐centre Australian experience

Objectives To evaluate the durability and predictors of loss of response of infliximab (IFX) over 2 years in paediatric Crohn's disease (CD) utilizing a proactive therapeutic drug monitoring (TDM) strategy. Methods A retrospective, single‐centre cohort study was conducted at The Children's Hospital at Westmead (CHW), Australia, from January 2019 to December 2021. Proactive TDM was performed at induction, end of induction and 6‐monthly thereafter. The primary outcome was switching to a different biologic as a marker of treatment failure. Secondary outcomes of a physician global assessment (PGA) scale, calprotectin, albumin and C‐reactive protein (CRP) levels were collected at induction, end of induction, 1‐year and 2‐year timepoints. Results Seventy‐nine patients were included (62% male, median age 13 years). Durability was 96% at 1 year and 88% at 2 years. Nine patients switched biologics with a median time of 57 weeks. Predictors of therapy failure included the need for escalated induction (odds ratio [OR] 8.5, p = 0.01) colonic phenotype (OR 9.7, p < 0.01), and post‐induction calprotectin level above 305 μg/g (positive predictive value 36%) were identified. Conclusions Utilizing a proactive TDM results in excellent durability of IFX at 2 years in paediatric CD. Colonic phenotype is an independent predictor for IFX failure, highlighting the need for directed therapy.