Quantitative contribution of six major transporters to the hepatic uptake of drugs: 'SLC-phenotyping' using primary human hepatocytes

Hepatic uptake transporters (solute carriers, SLCs), including organic anion transporting polypeptide (OATP)1B1, OATP1B3, OATP2B1, sodium-dependent taurocholate co-transporting polypeptide (NTCP), organic anion (OAT2) and organic cation (OCT1) transporters, play a key role in determining the systemic and liver exposure of chemically diverse drugs. Here, we established a phenotyping approach to quantify the contribution of the six SLCs, and passive diffusion, to the overall uptake using plated human hepatocytes (PHH). First, selective inhibitor conditions were identified by screening about 20 inhibitors across the six SLCs, using single-transfected HEK293 cells. Data implied rifamycin SV (20 µM) inhibits three OATPs, while rifampicin (5µM) inhibits OATP1B1/1B3 only. Further, hepatitis B virus myristoylated-preS1 peptide (HBVpep, 0.1 µM), quinidine (100 µM) and ketoprofen (100-300 µM) are relatively selective against NTCP, OCT1 and OAT2, respectively. Second, using these inhibitory conditions, the fraction transported (ft) by the individual SLCs was characterized for 20 substrates with PHH. Generally, extended clearance classification system (ECCS) class 1A/3A (e.g., warfarin) and 1B/3B compounds (e.g., statins) showed predominant OAT2 and OATP1B1/1B3 contribution, respectively. OCT1-mediated uptake was prominent for class 2/4 compounds (e.g., metformin). Third, in vitro ft values were corrected using quantitative proteomics data to obtained 9scaled ft9. Fourth, in vitro-in vivo extrapolation of the scaled OATP1B1/1B3 ft was assessed leveraging statin clinical drug-drug interaction data with rifampicin as perpetrator. Finally, we outlined a novel step-wise strategy to implement phenotypic characterization of SLC-mediated hepatic uptake for new molecular entities and drugs in a drug discovery and development setting.