Hartman J.C.,Gilead Sciences Inc. |
Brouwer K.,Qualyst Inc. |
Mandagere A.,Gilead Sciences Inc. |
Melvin L.,Gilead Sciences Inc. |
Gorczynski R.,Gilead Sciences Inc.
Canadian Journal of Physiology and Pharmacology | Year: 2010
To evaluate potential mechanisms of clinical hepatotoxicity, 4 endothelin receptor antagonists (ERAs) were examined for substrate activity and inhibition of hepatic uptake and efflux transporters in sandwich-cultured human hepatocytes. The 4 transporters studied were sodium-dependent taurocholate cotransporter (NTCP), organic anion transporter (OATP), bile salt export pump (BSEP), and multidrug resistance-associated protein 2 (MRP2). ERA transporter inhibition was examined using the substrates taurocholate (for NTCP and BSEP), [3H]estradiol-17β-D-glucuronide (for OATP), and [2-D-penicillamine, 5-D-penicillamine]enkephalin (for MRP2). ERA substrate activity was evaluated using probe inhibitors ritonavir (OATP and BSEP), bromosulfalein (OATP), erythromycin (P-glycoprotein), probenecid (MRP2 and OATP), and cyclosporin (NTCP). ERAs were tested at 2, 20, and 100 μmol.L-1 for inhibition and at 2 μmol.L-1 as substrates. OATP, NTCP, or BSEP transport activity was not reduced by ambrisentan or darusentan. Bosentan and sitaxsentan attenuated NTCP transport at higher concentrations. Only sitaxsentan decreased OATP transport (52%), and only bosentan reduced BSEP transport (78%). MRP2 transport activity was unaltered. OATP inhibitors decreased influx of all ERAs. Darusentan influx was least affected (84%-100% of control), whereas bosentan was most affected (32%-58% of control). NTCP did not contribute to influx of ERAs. Only bosentan and darusentan were shown as substrates for both BSEP and P-glycoprotein efflux. All ERAs tested were substrates for at least one hepatic transporter. Bosentan and sitaxsentan, but not ambrisentan and darusentan, inhibited human hepatic transporters, which provides a potential mechanism for the increased hepatotoxicity observed for these agents in the clinical setting. Source
Qualyst Inc. | Date: 2004-03-29
Diagnostic test kits for scientific use comprising of multi-well plates for measuring and characterizing protein binding.
Qualyst Inc. | Date: 2007-08-07
Diagnostic test kits for scientific use comprising of multi-well plates, fluorescent materials and chemi-luminescent materials for measuring metabolic properties.
Qualyst Inc | Date: 2007-10-30
Diagnostic kits consisting primarily of reagents, cultured mammalian cells, oligonucleotides, viral vectors, fluorescent probes, assay buffer solutions, and multi-well plate for scientific and research use.
Perry C.H.,Qualyst Inc. |
Smith W.R.,Qualyst Inc. |
Claire R.L.S.,Qualyst Inc. |
Brouwer K.R.,Qualyst Inc.
Journal of Biomolecular Screening | Year: 2011
Predictions of the absorption, distribution, metabolism, excretion, and toxicity of compounds in pharmaceutical development are essential aspects of the drug discovery process. B-CLEAR is an in vitro system that uses sandwich-cultured hepatocytes to evaluate and predict in vivo hepatobiliary disposition (hepatic uptake, biliary excretion, and biliary clearance), transporter-based hepatic drug-drug interactions, and potential drug-induced hepatotoxicity. Automation of predictive technologies is an advantageous and preferred format in drug discovery. In this study, manual and automated studies are investigated and equivalence is demonstrated. In addition, automated applications using model probe substrates and inhibitors to assess the cholestatic potential of drugs and evaluate hepatic drug transport are examined. The successful automation of this technology provides a more reproducible and less labor-intensive approach, reducing potential operator error in complex studies and facilitating technology transfer. (Journal of Biomolecular Screening. 2011;16:427-435) © 2011 Society for Laboratory Automation and Screening. Source