EARLY PROACTIVE THERAPEUTIC DRUG MONITORING OF INFLIXIMAB ACCELERATES TIME TO REMISSION IN CHILDREN WITH INFLAMMATORY BOWEL DISEASE

Abstract BACKGROUND In pediatric inflammatory bowel disease (IBD), proactive therapeutic drug monitoring (TDM) involves measuring infliximab (IFX) trough levels at pre-specified time points or intervals. Existing literature suggests that optimizing IFX dosing in response to levels at week 14, prior to the start of maintenance infusions, offers clinical benefit at 52 weeks. There has been growing interest in beginning proactive TDM earlier, prior to the 3rd and final induction infusion. We hypothesize that early proactive TDM prior to the 3rd versus 4th IFX infusion improves clinical outcomes in children with IBD. METHODS A retrospective cohort analysis included children with IBD receiving IFX treatment between January 1, 2020 and December 31, 2023. This study compared patients who underwent proactive TDM of IFX prior to the 3rd infusion (early group) versus those whose levels were first measured prior to the 4th infusion (later group). Propensity score matching was used to match patients based on gender, disease, and age at IFX start. Clinical and laboratory data, along with Physician Global Assessment (PGA), were collected at baseline and for one year following initiation of IFX and compared between the early and later groups. The primary outcomes were time to clinical remission based on PGA and therapeutic maintenance IFX levels (>5 μg/ml), IBD-related hospitalizations and surgeries, and discontinuation of IFX. Secondary outcomes evaluated clinical outcomes at 6- and 12-months post-IFX initiation in both groups. Time to event analysis including Kaplan Meier plots and log-rank tests were used to compare time to therapeutic maintenance between study groups. RESULTS In total, 68 patients from each group were matched. Patients from the early group experienced a faster median time to clinical remission of 140 days (95% CI: 108, 167) versus 203 days (95% CI: 167, 232) in patients from the later group (p < 0.05). While time to therapeutic maintenance IFX levels did not significantly differ across the entirety of both groups, 75% of patients from the early group achieved therapeutic levels in a median of 134 days (95% CI: 114, 182) versus 183 days (95% CI: 153, 224) in the later group. There were no significant differences in IFX discontinuation, hospitalizations, IBD-surgeries, or clinical outcomes at 6- and 12-months post-IFX initiation between the groups. CONCLUSIONS Early proactive TDM of IFX prior to the 3rd infusion may significantly accelerate time to clinical remission compared to later proactive TDM. It is suspected that measuring IFX trough levels earlier prior to the third infusion enables timely dose adjustments and promoted faster clinical improvement. Given its potential to enhance outcomes, early proactive TDM prior to the third infusion should be considered a valuable strategy in the clinical management of children with IBD.