Abstract

Suspended (SH), plated (PH) or sandwich-cultured human hepatocytes (SCHH) 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 if transporter-expressing cells (TEC) 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 TEC (OATPs/NTCP) and then scaled it to that in vivo by REF (the ratio of transporter abundance in human livers and TEC) determined by LC-MS/MS-based quantitative proteomics. Both the TEC and hepatocyte models did not meet our pre-defined success criteria of predicting within 2-fold the RSV CL_{uptake, in vivo} value obtained from our PET imaging. However, the TEC performed better than the hepatocyte models. Interestingly, using REF, TEC successfully predicted RSV CL_{int,uptake,hep} obtained by the hepatocyte models, suggesting that the underprediction of RSV CL_{uptake, in vivo} by TEC and hepatocytes is due to an endogenous factor(s) not present in these in vitro models. Therefore, we determined if inclusion of plasma (or albumin) in TEC uptake studies, improved IVIVE of RSV CL_{uptake, in vivo}. It did, but our predictions still fell shy of our pre-defined 2-fold lower boundary. Thus, 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.

Significance Statement We showed that the in vivo transporter-mediated uptake CL of rosuvastatin, determined by PET imaging, cannot be accurately predicted from in vitro studies in transporter-expressing cells (scaled using REF) or human hepatocytes (scaled based on mg of protein per g of liver). This conclusion held irrespective of whether albumin or plasma was included in the in vitro studies. Thus, additional studies are needed to improve IVIVE of transporter-mediated drug CL.