Simulated Dosing Regimens of Subcutaneous Infliximab in Adults and Children with Inflammatory Bowel Disease: Exploring Switch and Initiation Strategies.

Introduction: An increasing number of patients in clinical practice are transitioning from intravenous (IV) to subcutaneous (SC) dosing of infliximab. In this simulation study, we evaluated hypothetical dosing scenarios both for typical adults and adults with obesity and for children switching from steady-state IV to SC infliximab, as well as those initiating SC infliximab therapy.

Methods: By combining two previous published infliximab models, we were able to simulate both IV and SC dosing in adults and children. Various dosing regimens were simulated using a large virtual population. In each scenario, the distribution of trough concentrations and area under the plasma concentration-time curve (AUC) was calculated.

Results: Peak levels were higher after IV dosing compared with SC dosing, while trough levels were higher after SC dosing, leading to more stable infliximab levels over time. Overall exposure remained largely similar when switching from a standard IV to SC dosing regimen. Patients with a high body mass index and those on high-frequency IV dosing regimens of infliximab demonstrated reduced exposure when transitioned to the fixed SC dose. Paediatric patients exhibited higher exposure on the fixed SC dose. Simulation of SC induction schemes demonstrated early achievement of steady-state plasma levels.

Conclusion: Infliximab exposure (AUC) remains largely similar when transitioning from standard IV to SC dosing. Current dosing regimens may not be optimal for patients with severe obesity, paediatric patients and patients on high-frequency infliximab regimens. These findings provide a foundation for future clinical research to refine SC infliximab dosing in these populations.