Bridging Fixed Dose to Body Weight-based Regimen of Adalimumab in Paediatric Ulcerative Colitis Using a Pharmacometric Modelling Approach: Case Study with the Phase 3 ENVISION I Trial

Background and Aims: The Phase 3 study ENVISION I demonstrated efficacy and safety of adalimumab in paediatric patients with moderate to severe ulcerative colitis. The protocol-specified high-dose adalimumab regimen was numerically more efficacious than the standard-dose regimen. The objective of this work was to bridge a fixed-dosing regimen to the protocol-specified high-induction/high-maintenance, body weight-based dosing regimen studied in ENVISION I, using a pharmacometrics modelling and simulation approach. Methods: A stepwise strategy was implemented, including developing an adalimumab paediatric population pharmacokinetic model; using this model to determine a fixed-dosing regimen in paediatric ulcerative colitis patients which achieves similar concentrations to those observed in ENVISION I patients; determining adalimumab exposure-response relationship using population pharmacokinetic/pharmacodynamic model and data from ENVISION I; simulating clinical remission rate in paediatric ulcerative colitis patients using the Markov exposure-response model and the dosing regimen determined to provide similar efficacy to that observed in ENVISION I. Results: Both developed population pharmacokinetic and pharmacokinetic/pharmacodynamic models adequately described the observed data. Adalimumab exposure was identified as a significant predictor of clinical remission at Week 8 based on logistic regression [p <0.01]. Simulated efficacy suggested that the fixed-dosing regimen performs similarly to the more efficacious dosing regimen used in ENVISION I, by providing comparable clinical remission per Partial Mayo Score response rates over time. No relationship between adalimumab exposure and adverse events was identified. Conclusions: The population pharmacokinetic/pharmacodynamic model supports the appropriateness of the use of the fixed-dosing regimen in the paediatric ulcerative colitis population.