A semimechanistic pharmacokinetic/pharmacodynamic model for alanine aminotransferase‐based hepatotoxicity of methotrexate in paediatric patients with acute lymphoid leukaemia

Abstract

AimsMethotrexate (MTX) is recognized for its potential to induce hepatotoxicity, commonly manifested by elevated alanine aminotransferase (ALT) levels. However, the quantitative relationship between the pharmacokinetics (PK) of MTX and ALT‐based hepatotoxicity remains unclear. This study aimed to develop a semi‐mechanistic PK/pharmacodynamic (PD) model to characterize the MTX‐induced hepatotoxicity based on ALT in paediatric patients with acute lymphoid leukemia.MethodsA retrospective study was conducted on paediatric patients who received high‐dose (3‐5 g/m2) MTX treatment. MTX concentrations were assessed at 24‐hour intervals until the concentration dropped below 0.1 μmol/L. ALT concentrations were measured both before and after MTX administration. A population PK model was initially developed, which was later connected to a semi‐mechanistic hepatotoxicity model.ResultsThe PK model was developed using 354 MTX concentrations obtained from 51 patients, while the PD model was constructed using 379 ALT concentrations collected from 48 patients. The optimal PK model for MTX consisted of a two‐compartment structure, where body surface area served as a covariate for clearance and central volume of distribution. An indirect response model coupled to a liver injury signal transduction model was developed to describe the dynamics of ALT after MTX administration. The drug effect was adequately described by a linear model, exhibiting considerable inter‐occasion variability for each treatment session. No significant covariates were identified to have an impact on the PD parameters.ConclusionA semi‐mechanistic model was developed to describe ALT‐based hepatotoxicity of MTX, and it has the potential to serve as a valuable tool for characterizing drug‐induced hepatotoxicity.