Albumin-Mediated Uptake Improves Human Clearance Prediction for Hepatic Uptake Transporter Substrates Aiding a Mechanist
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Research Article Albumin-Mediated Uptake Improves Human Clearance Prediction for Hepatic Uptake Transporter Substrates Aiding a Mechanistic In Vitro-In Vivo Extrapolation (IVIVE) Strategy in Discovery Research Na Li,1,2 Akshay Badrinarayanan,1 Kazuya Ishida,1 Xingwen Li,1 John Roberts,1 Shuai Wang,1 Mike Hayashi,1 and Anshul Gupta1,2
Received 17 June 2020; accepted 16 October 2020 Abstract. This study focused on exploring various in vitro to in vivo extrapolation (IVIVE) approaches with the primary goal of improving human hepatic clearance (CL) prediction for OATP substrates. To that effect, the impact of albumin-mediated uptake in human hepatocytes was investigated. In vitro hepatic uptake assay using suspended human hepatocytes was performed with 16 selected OATP substrates to determine the uptake CL in the absence and presence of 4% BSA and unbound hepatocyte to media partition coefficient (Kpuu). Substantial enhancement of the unbound uptake CL (PSu,inf) was observed in the presence of 4% BSA, demonstrating “albumin-mediated” uptake. Prediction of human hepatic CL was performed using two non-traditional IVIVE approaches: initial uptake CL (PSu,inf) and intrinsic metabolic CL (CLint,met) corrected by Kpuu based on extended clearance concept. Compared to traditional IVIVE using CLint,met only, the two tested IVIVE approaches significantly improved the prediction of human hepatic CL. Particularly, direct extrapolation from PSu,inf (+BSA) showed the most robust correlation with in vivo human hepatic CL for all 16 compounds with bias of 1.9–2.0 for two lots of human hepatocytes, respectively. In addition, PSu,inf (+BSA) and Kpuu were also determined in suspended cynomolgus monkey hepatocytes. Prediction of monkey hepatic CL was improved by both approaches, although with more bias compared to human. These results suggested supplementing 4% BSA in human hepatocyte uptake assay provides a useful tool to characterize hepatic uptake CL for OATP substrates, enabling more accurate human CL prediction without any empirical scaling factor (ESF). KEY WORDS: hepatic uptake; human clearance prediction; in vitro to in vivo extrapolation; OATP and albumin.
INTRODUCTION 1
Department of Pharmacokinetics and Drug Metabolism, Amgen Research, Amgen Inc, 360 Binney St, Cambridge, Massachusetts 02142, USA. 2 To whom correspondence should be addressed. (e–mail: [email protected]; [email protected]) Abbreviations: AAFE, Absolute average fold error; BSA, Bovine serum albumin; CL, Clearance; CLint,all, Hepatic intrinsic clearance; CLint,met, Intrinsic hepatic metabolic clearances; CYP, Cytochrome P450; DDI, Drug-drug interaction; ECCS, Extended clearance classification system; ESF, Empirical scaling factor; fu,p, The unbound fraction in plasma; fu,hep, The unbound fraction in hepatocyte suspension incubation; fu,liver tissue, The unbound fraction in liver tissue; fu,KHB w 4%,BSA, Unbound fraction in KHB buffer containing 4% BSA; IVIVE, In vitro to in vivo extrapolation; KHB, KrebsHenseleit buffer; Kpuu,ss, Unbound hepatocy
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