Transporter-mediated alterations in bile acid disposition may have significant toxicological implications. Current methods to predict interactions are limited by the interplay of multiple transporters, absence of protein in the experimental system, and inaccurate estimates of inhibitor concentrations. An integrated approach was developed to predict altered bile acid disposition due to inhibition of multiple transporters using the model bile acid taurocholate (TCA). TCA pharmacokinetic parameters were estimated by mechanistic modeling using sandwich-cultured human hepatocyte data with protein in the medium. Uptake, basolateral efflux, and biliary clearance estimates were 0.63, 0.034, and 0.074 mL/min/g liver, respectively. Cellular total TCA concentrations (Ct,Cells) were selected as the model output based on sensitivity analysis. Monte Carlo simulations of TCA Ct,Cells in the presence of model inhibitors (telmisartan and bosentan) were performed using inhibition constants for TCA transporters and inhibitor concentrations, including cellular total inhibitor concentrations ([I]t,cell) or unbound concentrations, and cytosolic total or unbound concentrations. For telmisartan, the model prediction was accurate with an average fold error (AFE) of 0.99–1.0 when unbound inhibitor concentration ([I]u) was used; accuracy dropped when total inhibitor concentration ([I]t) was used. For bosentan, AFE was 1.2–1.3 using either [I]u or [I]t. This difference was evaluated by sensitivity analysis of the cellular unbound fraction of inhibitor (fu,cell,inhibitor), which revealed higher sensitivity of fu,cell,inhibitor for predicting TCA Ct,Cells when inhibitors exhibited larger ([I]t,cell/IC50) values. In conclusion, this study demonstrated the applicability of a framework to predict hepatocellular bile acid concentrations due to drug-mediated inhibition of transporters using mechanistic modeling and cytosolic or cellular unbound concentrations.
- Received January 24, 2016.
- Accepted May 26, 2016.
This work was supported by the National Institutes of Health National Institute of General Medical Sciences [Grant R01GM041935]. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. C.G. is supported, in part, by the University of North Carolina Royster Society of Fellows.
This work was previously presented, in part, as a poster presentation at the following workshops: Guo C, Brouwer KR, Yang K, St. Claire R, and Brouwer, KLR (2014) Prediction of altered bile acid disposition by drugs using an integrated approach: Sandwich-cultured human hepatocytes, mechanistic modeling and simulation, in 19th North American International Society for the Study of Xenobiotics (ISSX) Meeting/29th Japanese Society for the Study of Xenobiotics (JSSX) Meeting; 2014 Oct 19-23; San Francisco, CA. ISSX, Washington, DC; and Guo C, Yang K, and Brouwer KLR (2015) Prediction of hepatic efflux transporter-mediated DDIs: When does variability in IC50 or intracellular unbound fraction of inhibitors matter? 20th North American ISSX Meeting; 2015 Oct 18-22; Orlando, FL. ISSX, Washington, DC.
B-CLEAR is covered by US Pat. No. 6,780,580 and other US and International patents both issued and pending.
Dr. K.L.R. Brouwer is a co-inventor of the sandwich-cultured hepatocyte technology for quantification of biliary excretion (B-CLEAR) and related technologies, which have been licensed exclusively to Qualyst Transporter Solutions, LLC. Dr. K.R. Brouwer and Dr. R.L. St. Claire are employed by Qualyst Transporter Solutions, LLC.
↵1 Current affiliation: DILIsym Services Inc., Research Triangle Park, North Carolina
- Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics