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Daniel Scotcher

2021 Drug Metabolism Discussion Group and Swedish Academy of Pharmaceutical Sciences Online Joint Meeting

Abstract

Physiologically-based pharmacokinetic (PBPK) modelling provides a framework for in vitro-in vivo extrapolation (IVIVE) of drug disposition. Quantitative prediction of transporter-mediated processes and tissue permeation remains challenging due to the lack of available in vivo tissue data for model validation. Gadoxetate is a magnetic resonance imaging (MRI) contrast agent and substrate of organic anion transporting polypeptide 1B1 (OATP1B1) and multidrug resistance-associated protein 2 (MRP2). Gadoxetate is being explored as a novel imaging biomarker for hepatic transporter function in context of evaluation of drug-drug interactions and drug induced liver injury. The in vitro uptake kinetics of gadoxetate in plated rat hepatocytes were assessed, and transporter kinetic parameters derived using a mechanistic cell model. Subsequently, a novel PBPK model was developed for gadoxetate in rat, where liver uptake and cellular binding were informed by IVIVE. Gadoxetate in vivo blood, spleen and liver data obtained in the presence and absence of a single 10 mg/kg intravenous dose of rifampicin were used for PBPK model refinement. The PBPK model successfully predicted gadoxetate concentrations in systemic blood and spleen and corresponding increase in gadoxetate systemic exposure in the presence of rifampicin, whereas liver concentrations were under-predicted. Refinement of the PBPK model using the dynamic contrast agent enhanced (DCE)-MRI data enabled recovery of the liver profile. The current study demonstrates utility of tissue imaging data in validating and refining PBPK models for prediction of transporter-mediated disposition.