Baseline Drug Clearance Predicts Outcomes in Children With Inflammatory Bowel Disease Treated With Vedolizumab: Results From the VedoKids Prospective Multicentre Study

Background: The pharmacokinetics of biologic agents can differ between children and adults with inflammatory bowel disease (IBD), often necessitating modified paediatric dosing strategies. Aims: To define the exposure-response relationship of vedolizumab in the paediatric IBD VedoKids cohort including the effect of baseline clearance on deep biochemical remission (normal C-reactive protein [CRP]/erythrocyte sedimentation rate [ESR] and steroid-free remission) at 30 weeks, and to use population pharmacokinetic models to find the best matches between adult and paediatric pharmacokinetic profiles. Methods: We sought a pharmacokinetic model on 312 serum vedolizumab concentrations from 129 children, assisted by a published adult model as a Bayesian prior. We employed the model for exposure-response evaluation and for investigating doses in paediatric patients to match the adult exposure at the labelled dose. Results: At Week 30, 104/129 (81%) children (53% female and 47% Crohn disease) remained on vedolizumab, of whom 39 (31%) in the exposure-response evaluation were in deep biochemical remission. Increased baseline drug clearance was associated with lower deep biochemical remission rates at Week 30 based on ESR/CRP (OR 0.47 [95% CI 0.2-1.05, p = 0.08]) and calprotectin < 100 mu g/g (OR 0.13 [95% CI 0.1-0.79, p < 0.05]). Higher weight and lower serum albumin were associated with increased clearance (p < 0.001). Simulation models found that, for children <= 30 kg, tiered fixed dosing regimens best matched adult drug concentrations. Conclusions: Drug clearance was strongly influenced by serum albumin. Baseline clearance predicted deep biochemical remission at Week 30. Further investigation is needed to better understand optimal dosing strategies-especially for lower-weight children receiving vedolizumab.