Adequate translation of parameters from in vitro experiments to in vivo requires a proper characterisation and mechanistic representation of the systems. The aim of this study was to apply a mechanistic model to better characterise the data from experiments involving in vitro cell lines transfected with ABCB1 genes. In vitro bi-directional transport data (compound recoveries, apparent permeabilities (Papp) and efflux ratios (ER)) were generated from mock and transfected cell lines of Madin-Darby canine kidney type 1 (MDCK I) and type II (MDCK II), as well as a pig kidney-derived cell lines (LLC-PK 1 ). These were transfected/transduced with either rat (LLC-PK 1 /Mdr1a and MDCK I/Mdr1a) or human (LLC-PK 1 /MDR1 and MDCK II/MDR1) P-glycoprotein (P-gp) cDNAs. The compounds tested included donepezil, loperamide, phenytoin, quinidine, risperidone, and verapamil. Also, a mechanistic model was used to analyse the data. ER was 2 for transfected cell lines, particularly for compounds that are P-gp substrates. The mechanistic model provided a better fit to the observed data, enabling more accurate estimation of both passive and active transport parameters. Nonspecific binding estimates were slightly higher on the apical side (mean: 0.76; range: 0.49–1.00) compared to the basolateral side (mean: 0.71; range: 0.43–0.90). Passive and active clearance values were approximately two-fold higher with the mechanistic model than with the conventional model (passive: 0.17–5.65; active: 1.31–4.88). Overall, the mechanistic model provides parameter estimates that are consistent across species and cell lines, making them more suitable for translation to in vivo systems.
Hogan et al. (2026) studied this question.