Abstract

Suspended, plated, or sandwich-cultured human hepatocytes are routinely used for in vitro to in vivo extrapolation (IVIVE) of transporter-mediated hepatic clearance (CL) of drugs. However, these hepatocyte models have been reported to underpredict transporter-mediated in vivo hepatic uptake CL (CL_{uptake,in vivo}) of some drugs. Therefore, we determined whether transporter-expressing cells (TECs) can accurately predict the CL_{uptake,in vivo} of drugs. To do so, we determined the uptake CL (CL_{int,uptake,cells}) of rosuvastatin (RSV) by TECs (organic anion transporting polypeptides/Na⁺-taurocholate cotransporting polypeptide) and then scaled it to that in vivo by relative expression factor (REF) (the ratio of transporter abundance in human livers and TEC) determined by liquid chromatography tandem mass spectrometry–based quantitative proteomics. Both the TEC and hepatocyte models did not meet our predefined success criteria of predicting within 2-fold the RSV CL_{uptake,in vivo} value obtained from our positron emission tomography (PET) imaging. However, the TEC performed better than the hepatocyte models. Interestingly, using REF, TECs successfully predicted RSV CL_{int,uptake,hep} obtained by the hepatocyte models, suggesting that the underprediction of RSV CL_{uptake,in vivo} by TECs and hepatocytes is due to endogenous factor(s) not present in these in vitro models. Therefore, we determined whether inclusion of plasma (or albumin) in TEC uptake studies improved IVIVE of RSV CL_{uptake,in vivo}. It did, and our predictions were close to or just fell above our lower 2-fold acceptance boundary. Despite this success, additional studies are needed to improve transporter-mediated IVIVE of hepatic uptake CL of drugs. However, using REF and TEC, we successfully predicted the magnitude of PET-imaged inhibition of RSV CL_{uptake,in vivo} by cyclosporine A.