Population pharmacokinetic analysis in children with different diseases treated with mycophenolate mofetil-Integrated analysis of clinical trials and real-world clinical data.

Objectives: This study aims to develop a population pharmacokinetic (PK) model of mycophenolic acid (MPA) in pediatric patients with different diseases.

Methods: To develop the PK model, electronic medical records (EMR) of pediatric patients with different diseases who received mycophenolic acid mofetil (MMF) at the National Center for Child Health and Development from February 2013 to May 2022 and the results of the MMF pharmacokinetic study of pediatric complicated frequently relapsing steroid-dependent nephrotic syndrome under the Advanced Medical Care B protocol (JSKDC09 study) from October 2015 to June 2019 were integrated and analyzed. Non-linear mixed-effects modeling was used to 1) develop a cross-disease population PK model and 2) estimate PK parameters (apparent clearance CL/F and Q/F; apparent volume of distribution Vc/F and Vp/F; absorption rate constant Ka) by post-hoc Bayesian methods. Patient backgrounds, concomitant medications, and laboratory data were included in the covariate analysis. Visual predictive checks with bootstrap and predictive correction were performed to evaluate the final model.

Results: A total of 249 patients with 1495 measurements were used in the analysis, including 68 with post-liver transplant, 65 with nephrotic syndrome, 28 with post-renal transplant, 31 with autoimmune diseases (17 with lupus nephritis and 14 with other collagen diseases), 13 with hematopoietic stem cell transplantation, and 5 with others from EMR and 39 with nephrotic syndrome from the JSKDC09 study. A two-compartment model with a first-order rate absorption process best explained the PK of MPA. A nonlinear relationship between dose and MPA exposure was observed and described by the power function of the model. The final population mean PK parameter estimates (95 % confidence interval) for non-renal transplant patients and average albumin levels were CL/F 15.2 (13.3, 18.0) L/h/70 kg, Vc/F 15.4 (14.4, 17.2) L, Vp/F 246.8 (159.1, 332.1) L, Q/F 7.0 (5.0, 9.0) L/h, and Ka (without proton pump inhibitor [PPI]) 4.4 (2.4, 4.9) h. Weight, disease (post-renal transplant), and serum albumin level were significant covariates for CL/F, and serum albumin level for Vc/F. The use of PPIs also affected Ka.

Conclusions: An integrated population PK model of MPA was developed in children with the following conditions: post-solid organ transplantation, post-HSCTx, autoimmune disease, and nephrotic syndrome. Estimated parameters and parameter covariates were similar to those previously reported. This model is expected to provide useful information for using MPA in various diseases in the Japanese population.