Infliximab in young paediatric IBD patients: it is all about the dosing

Infliximab (IFX) is administered intravenously using weight-based dosing (5 mg/kg) in inflammatory bowel disease (IBD) patients. Our hypothesis is that especially young children need a more intensive treatment regimen than the current weight-based dose administration. We aimed to assess IFX pharmacokinetics (PK), based on existing therapeutic drug monitoring (TDM) data in IBD patients < 10 years. TDM data were collected retrospectively in 14 centres. Children treated with IFX were included if IFX was started as IBD treatment at age < 10 years (young patients, YP) and PK data were available. Older IBD patients aged 10-18 years were used as controls (older patients, OP). Two hundred and fifteen paediatric inflammatory bowel disease (PIBD) patients were eligible for the study (110 < 10 year; 105 >= 10 years). Median age was 8.3 years (IQR 6.9-8.9) in YP compared with 14.3 years (IQR 12.8-15.6) in OP at the start of IFX. At the start of maintenance treatment, 72% of YP had trough levels below therapeutic range (< 5.4 mu g/mL). After 1 year of scheduled IFX maintenance treatment, YP required a significantly higher dose per 8 weeks compared with OP (YP; 9.0 mg/kg (IQR 5.0-12.9) vs. OP; 5.5 mg/kg (IQR 5.0-9.3);p < 0.001). The chance to develop antibodies to infliximab was relatively lower in OP than YP (0.329 (95% CI - 1.2 to - 1.01);p < 0.001), while the overall duration of response to IFX was not significantly different (after 2 years 53% (n = 29) in YP vs. 58% (n = 45) in OP;p = 0.56). Conclusion: Intensification of the induction scheme is suggested for PIBD patients aged < 10 years. What is Known?