Prediction of hepatic metabolic clearance in rats and dogs using long-term cocultured hepatocytes

Knowledge of the accuracy of in vitro to in vivo extrapolation (IVIVE) in preclinical species pharmacokinetics is often used to assess the reliability of physiologically based modeling to predict clinical pharmacokinetics of new chemical entities. In this study, the in vitro hepatic clearance was evaluated using suspended hepatocytes and long-term cocultured hepatocytes for 27 internal drug candidates, and 20 (dogs) or 24 (rats) marketed drugs. Prospective identification of rate-determining step(s) was performed through application of the Extended Clearance Classification System. The HepatoPac, suitable for the assessment of low metabolic turnover in humans, did not demonstrate significant superiority of the metabolic clearance prediction in rats and dogs relative to suspended hepatocytes using a set of the internal drug candidates. A 3.6- to 5.9-fold underestimation of the upscaled unbound intrinsic clearance (CL_int,h,u) for Extended Clearance Classification System 1a/2 compounds was determined in rats and dogs throughout the study. Limited predictability of the active transport clearance using both liver preparations was confirmed with a 9.8- to 213-fold error. Nonetheless, for compounds with CL_int,h ≤ 3 μL/min/mg in suspended hepatocytes, reassessment of CL_int,h using HepatoPac can be still considered to achieve a reasonable IVIVE. For marketed drugs, the in vitro CL_int,h,u values obtained from hepatocyte suspensions and HepatoPac were consistent with the in vivo clearance data in rats and dogs with a few exceptions. Species differences in some drug-metabolizing enzymes were highlighted as potential hindrance to clearance IVIVE in preclinical species and humans. SIGNIFICANCE STATEMENT: The current findings provide insights into the differences and similarities between in vitro clearance measurements using hepatocyte suspension assays and HepatoPac, and their translation to in vivo clearance values in rats and dogs. In addition, a gap analysis was performed discussing species differences of the drug-metabolizing enzyme isoforms to complement the current strategy of predicting human pharmacokinetics prior to phase 1 with physiologically based pharmacokinetic modeling.