Absolute abundance and function of intestinal drug transporters: a prerequisite for fully mechanistic in vitro–in vivo extrapolation of oral drug absorption

Abstract

The use of whole body physiological-based pharmacokinetic (PBPK) models linked with in vitro-in vivo extrapolation (IVIVE) of kinetic parameters from laboratory experiments, has become embedded within many of the pharmaceutical industry and is used even as part of regulatory submissions. These include the influence of transporter proteins on drug disposition, a subject for which we have witnessed an increasing awareness. A combination of the development of high-powered analytical techniques and antibody-based technology, together with a realization that an understanding of absolute transporter protein abundances together with activity can potentially enhance the modelling of transporter kinetics by PBPK-IVIVE link models. This review summarizes the mechanistic approaches to integrate suitable non-biased in vitro transporter kinetic data relevant to the intestine (i.e. 'intrinsic' K i , 'intrinsic' K m ), by in vitro system modelling for these kinetic inputs with the advantages of, and challenges for, generating these data for input into PBPK models. This step is considered as a prerequisite for mechanistic modelling of the oral absorption for drugs that are substrates for transporters. Various approaches are provided to integrate intestinal transporter expression into PBPK models with a perspective on the incorporation of the absolute abundance/activity of transporters to enhance the predictive power of the models. We define the key intestinal tissue and functional expression-based scaling factors required. The objective is to use these for facilitating the extrapolation from in vitro intestinal transporter assays to the in vivo system, using absolute quantification methodologies. The models could be used to elucidate the complex relationship and relative importance of metabolizing enzymes and transporters in drug disposition and toxicity.

Lost in Centrifugation: Accounting for Transporter Protein Losses in Quantitative Targeted Absolute Proteomics

“…Moreover, since protein expression is usually quoted as moles per mass of protein in the subcellular fraction, differing complements of organelles and protein in the fractions being quantified limit comparison of results between studies. Within an IVIVE strategy, functional transporter abundances are advocated for the generation of mechanistic scaling factors and are incorporated into organ models within PBPK models (Harwood et al, 2013). Any underestimation in transporter abundance and function within the PBPK model could lead to a predicted reduction in the impact of a transporter protein(s) function on drug disposition after simulation, resulting in pharmacokinetic outcomes that are not observed in the clinic.…”

Interindividual Variability in Hepatic Organic Anion-Transporting Polypeptides and P-Glycoprotein (ABCB1) Protein Expression: Quantification by Liquid Chromatography Tandem Mass Spectroscopy and Influence of Genotype, Age, and Sex

“…Consequently, these transporters can affect the efficacy (Bailey et al, 2010;Tomlinson et al, 2010) and toxicity (Alexandridis et al, 2000;Bosch Rovira et al, 2001;Marsa Carretero et al, 2002) of drugs by modulating their exposure to the target sites (Harwood et al, 2013). Hence, it is important to delineate the role of hepatic transporters in drug disposition and local tissue drug exposure, particularly because plasma drug concentrations are generally used as a surrogate measure of tissue concentrations to describe pharmacokineticpharmacodynamic relationships and to predict drug-drug interactions (DDIs) or drug-gene interactions (Lon et al, 2012;Harwood et al, 2013). To achieve these goals on a population basis, physiologically based pharmacokinetic (PBPK) models (e.g., Simcyp) are increasingly being used in drug development and pharmaceutical research (Varma et al, 2012(Varma et al, , 2013.…”

“…To achieve these goals on a population basis, physiologically based pharmacokinetic (PBPK) models (e.g., Simcyp) are increasingly being used in drug development and pharmaceutical research (Varma et al, 2012(Varma et al, , 2013. For drugs where transporters are involved in their disposition, successful use of PBPK models requires critical information on the tissue localization and expression of the transporters, including the effect of covariates, like genotype, age, and sex, on transporter expression (Deo et al, 2012;Chu et al, 2013;Harwood et al, 2013;Prasad et al, 2013). However, such data are currently not available.…”

Non-animal approaches for toxicokinetics in risk evaluations of food chemicals

“…Though Caco-2 cells are proficient in the main transporters, including P-glycoprotein (PgP), multidrug resistance protein 2 (MRP2), and breast cancer resistance proteins (BCRP), expression levels of these transporters are generally quite variable (Larregieu and Benet, 2013;Harwood et al, 2013Harwood et al, , 2016. In addition, the under-expression of transporters such as peptide transporter 1 (PEPT1), organic cation transporters (OCTs), and organic anion transporters (OATs), makes the model less suitable for compounds that use these transporters (Larregieu and Benet, 2013).…”

“…Work on the human hepatoma cell line HepaRG is particularly promising. HepaRG cells express various cytochrome P450 and phase II enzymes when maintained in a differentiated state (Harwood et al, 2013;Zanelli et al, 2011).…”