A Physiological-Based Pharmacokinetic Model Embedded with a Target-Mediated Drug Disposition Mechanism Can Characterize Single-Dose Warfarin Pharmacokinetic Profiles in Subjects with Various CYP2C9 Genotypes under Different Cotreatments

Warfarin, a commonly prescribed oral anticoagulant medication, is highly effective in treating deep vein thrombosis and pulmonary embolism. However, the clinical dosing of warfarin is complicated by high interindividual variability in drug exposure and response and its narrow therapeutic index. CYP2C9 genetic polymorphism and drug-drug interactions (DDIs) are substantial contributors to this high variability of warfarin pharmacokinetics (PK), among numerous factors. Building a physiology-based pharmacokinetic (PBPK) model for warfarin is not only critical for a mechanistic characterization of warfarin PK but also useful for investigating the complicated dose-exposure relationship of warfarin. Thus, the ob-jective of this study was to develop a PBPK model for warfarin that integrates information regarding CYP2C9 genetic polymorphisms and their impact on DDIs. Generic PBPK models for both S-and R-warfarin, the two enantiomers of warfarin, were constructed in R with the mrgsolve package. As expected, a generic PBPK model structure did not adequately characterize the warfarin PK profile collected up to 15 days following the administration of a single oral dose of warfarin, especially for S-warfarin. However, following the integration of an empirical target-mediated drug disposition (TMDD) component, the PBPK-TMDD model well characterized the PK profiles collected for both S-and R-warfarin in subjects with different CYP2C9 genotypes. Following the integration of en-zyme inhibition and induction effects, the PBPK-TMDD model also characterized the PK profiles of both S-and R-warfarin in var-ious DDI settings. The developed mathematic framework may be useful in building algorithms to better inform the clinical dosing of warfarin.SIGNIFICANCE STATEMENT The present study found that a traditional physiology-based phar-macokinetic (PBPK) model cannot sufficiently characterize the pharmacokinetic profiles of warfarin enantiomers when warfarin is administered as a single dose, but a PBPK model with a target -mediated drug disposition mechanism can. After incorporating CYP2C9 genotypes and drug-drug interaction information, the de-veloped model is anticipated to facilitate the understanding of war-farin disposition in subjects with different CYP2C9 genotypes in the absence and presence of both cytochrome P450 inhibitors and cytochrome P450 inducers.

Automated summary

Warfarin is highly effective in treating deep vein thrombosis and pulmonary embolism, but its clinical dosing is complicated by high variability in drug exposure and response. This study developed a physiology-based pharmacokinetic (PBPK) model for warfarin that incorporates genetic polymorphisms and drug-drug interactions, providing insights into individual variability and dose-exposure relationship.