The combined application of PBPK model and PopPK model in the dose selection of pediatric drug development: an example of rivaroxaban

Model-informed drug development (MIDD) in the development of pediatric drugs is drawing more and more attention due to the insufficiency of subjects, lack of research on ontogeny, and the limitation of ethic. The core of MIDD used for dose selection includes the population pharmacokinetic (PopPK) model and physiologically based pharmacokinetic (PBPK) model, as well as model-based simulation and prediction. PBPK model has the advantage of predicting the optimal pediatric dose before the clinical trials and has the ability of extrapolation from adult model to pediatric model. PopPK model characterizes the pediatric PK feature based on the analysis of clinical data and can be used to explore the significant covariates, which is a power tool for individualized medicine in children. With their own advantages and disadvantages, PBPK and PopPK model should be jointly used in the pediatric drug development to refine the dose regimen for children at different ages. In this study, the pediatric drug development of rivaroxaban was taken as an example to introduce the combined application of PBPK model and PopPK model in the design and validation of pediatric dose regimen in Phase Ⅰ, Ⅱ and Ⅲ trials, which may provide reference to MIDD in other pediatric drug development.