Using human recombinant UDP-glucuronosyltransferase isoforms and a relative activity factor approach to model total body clearance of laropiprant (MK-0524) in humans

Abstract

1. A major pathway of elimination of the prostaglandin D₂ receptor 1 antagonist laropiprant in humans is by uridine diphosphate-glucuronosyltransferase (UGT)-mediated biotransformation. In this study, liver and kidney relative activity factors were developed for UGT1A1, 1A9 and 2B7 to allow for in vitro–in vivo extrapolation of intrinsic clearance data to whole organ clearance using recombinant human UGT isoforms applying this to laropiprant as a model substrate.

2. The total body metabolic clearance of laropiprant determined using this approach (5.0 L/hr) agreed well with the value determined in vivo following intravenous administration to healthy human volunteers (5.1 L/hr).

3. The results suggest that approximately 36%, 36% and 28% of the hepatic metabolic clearance of laropiprant was mediated by UGT1A1, 1A9 and 2B7, respectively. Likewise, 80% and 20% of the renal metabolic clearance was mediated by UGT1A9 and 2B7, respectively. Furthermore, the data suggested that the contribution of the kidney to the overall total metabolic clearance was minor relative to the liver (∼ 12%).

• Human intravenous pharmacokinetics
• IVIVE
• prostaglandin D₂ receptor 1 antagonist

Acknowledgements

The authors would like to thank Drs Lisa Shipley and Nancy Agrawal (PPDM, Merck Research Laboratories) for providing an environment under which this work was possible and to Nancy for providing helpful comments on this manuscript. We also thank Dr Sibylle Neuhoff (simCYP Ltd. now Certara) and Dr Bindhu Karanam (PPDM, Merck Research Laboratories) for their insight and discussions during the preparation of this manuscript.