Hepatic OATP-mediated clearance in the Beagle dog: assessing in vitro-in vivo relationships and applying cross species empirical scaling factors to improve prediction of human clearance

In the present study the beagle dog was evaluated as a preclinical model to investigate organic anion transporting polypeptide (OATP)-mediated hepatic clearance. In vitro studies were performed with nine OATP substrates in three lots of plated male dog hepatocytes +/- OATP inhibitor cocktail to determine total uptake (CL uptake ), total and unbound cell-to-medium concentration ratio (Kp uu ). In vivo intrinsic hepatic clearances (CL int,H ) were determined following intravenous drug administration (0.1 mg/kg) in male beagle dogs. The in vitro parameters were compared to those previously reported in plated human, monkey and rat hepatocytes; the ability of cross species scaling factors to improve prediction of human in vivo clearance was assessed. CL uptake in dog hepatocytes ranged from 9.4-135 µL/min/10 6 cells for fexofenadine and telmisartan, respectively. Active process contributed >75% to CL uptake for 5/9 drugs. Rosuvastatin and valsartan showed Kp uu >10, whereas cerivastatin, pitavastatin, repaglinide and telmisartan had Kp uu <5. The extent of hepatocellular binding in dog was consistent with other preclinical species and humans. The bias (2.73-fold) obtained from comparison of predicted vs. in vivo dog CL int,H was applied as an average empirical scaling factor (ESF av ) for in vitro-in vivo extrapolation of human CL int,H . The ESF av based on dog reduced under-prediction of human CL int,H for the same dataset (gmfe=2.1), highlighting its utility as a preclinical model to investigate OATP-mediated uptake. The ESF av, from all preclinical species resulted in comparable improvement of human clearance prediction, in contrast to drug specific empirical scalars, rationalized by species differences in expression and/or relative contribution of particular transporters to drug hepatic uptake. were compared across all preclinical species investigated. The extent of improvement in human clearance prediction based on application of ESFs from beagle dog was compared to the application of ESFs from monkey and rat data for the same dataset of OATP substrates. 0.58, 0.75, 1, 1.5, 2.5, 4.5, 8.5, 12.5 and 24.5 h following administration. Blood samples were collected in tubes containing EDTA and centrifuged to collect plasma. Studies were carried out in cages with plexiglass surroundings for collection of urine from 0-4, 4-8, 8-12, and 12-24 h. Additional blood samples were taken at pre-dose, 4, 8, 12, and 24 h for measurement of plasma creatinine. Creatinine was also measured in an aliquot from each urine collection interval. Plasma and urine samples for determination of Differences in fexofenadine, pravastatin and valsartan were particularly marked, as dog Kp parameters to 6.2- greater than values obtained in monkey. The overall trends seen between dog and monkey Kp parameters were evident also in the comparison of dog and human Kp and Kp uu , with the exception of valsartan. Even though Kp and Kp uu showed species-dependent values, there was a good agreement in intracellular binding parameter across species. This trend was particularly strong between dog and monkey fu cell data (1.76-fold bias), whereas 2.3- and 2.6-fold difference was seen in dog fu cell relative to rat and human data, respectively. OATP interplay, of the sd distinct trends between the preclinical