Pharmacokinetics Dynamics and Metabolism, Pfizer Global Research and Development, Pfizer Inc., Groton, Connecticut.
Pharmacokinetics Dynamics and Metabolism, Pfizer Global Research and Development, Pfizer Inc., Groton, Connecticut
J Pharmacol Exp Ther. 2018 Mar;364(3):390-398. doi: 10.1124/jpet.117.245951. Epub 2018 Jan 11.
Tolbutamide is primarily metabolized by CYP2C9, and, thus, is frequently applied as a clinical probe substrate for CYP2C9 activity. However, there is a marked discrepancy in the in vitro-in vivo extrapolation of its metabolic clearance, implying a potential for additional clearance mechanisms. The goal of this study was to evaluate the role of hepatic uptake transport in the pharmacokinetics of tolbutamide and to identify the molecular mechanism thereof. Transport studies using singly transfected cells expressing six major hepatic uptake transporters showed that tolbutamide is a substrate to organic anion transporter 2 (OAT2) alone with transporter affinity [Michaelis-Menten constant ()] of 19.5 ± 4.3 M. Additionally, OAT2-specific transport was inhibited by ketoprofen (an OAT2 inhibitor) and 1 mM rifamycin SV (pan inhibitor), but not by cyclosporine and rifampicin (OAT polypeptides/Na-taurocholate cotransporting polypeptide inhibitors). Uptake studies in primary human hepatocytes confirmed the predominant role of OAT2 in the active uptake with significant inhibition by rifamycin SV and ketoprofen, but not by the other inhibitors. Concentration-dependent uptake was noted in human hepatocytes with active transport characterized by and values of 39.3 ± 6.6 M and 426 ± 30 pmol/min per milligram protein, respectively. Bottom-up physiologically based pharmacokinetic modeling was employed to verify the proposed role of OAT2-mediated hepatic uptake. In contrast to the rapid equilibrium (CYP2C9-only) model, the permeability-limited (OAT2-CYP2C9 interplay) model better described the plasma concentration-time profiles of tolbutamide. Additionally, the latter well described tolbutamide pharmacokinetics in carriers of genetic variants and quantitatively rationalized its known drug-drug interactions. Our results provide first-line evidence for the role of OAT2-mediated hepatic uptake in the pharmacokinetics of tolbutamide, and imply the need for additional clinical studies in this direction.
甲苯磺丁脲主要通过 CYP2C9 代谢，因此常被用作 CYP2C9 活性的临床探针底物。然而，其代谢清除率的体外-体内外推存在显著差异，这意味着可能存在其他清除机制。本研究旨在评估肝摄取转运在甲苯磺丁脲药代动力学中的作用，并确定其分子机制。使用表达六种主要肝摄取转运体的单转染细胞进行转运研究表明，甲苯磺丁脲是有机阴离子转运蛋白 2（OAT2）的底物，转运体亲和力[米氏常数()]为 19.5 ± 4.3 M。此外，OAT2 特异性转运被酮洛芬（OAT2 抑制剂）和 1 mM 利福霉素 SV（泛抑制剂）抑制，但不受环孢素和利福平（OAT 多肽/Na-牛磺胆酸盐共转运蛋白抑制剂）抑制。原代人肝细胞摄取研究证实了 OAT2 在主动摄取中的主要作用，利福霉素 SV 和酮洛芬显著抑制，而其他抑制剂则没有。在人肝细胞中观察到浓度依赖性摄取，主动转运的特征是 ，和 值分别为 39.3 ± 6.6 M 和 426 ± 30 pmol/min per milligram protein。自上而下的基于生理学的药代动力学模型被用来验证 OAT2 介导的肝摄取的拟议作用。与快速平衡（仅 CYP2C9）模型相比，渗透限制（OAT2-CYP2C9 相互作用）模型更好地描述了甲苯磺丁脲的血浆浓度-时间曲线。此外，后者很好地描述了遗传变异携带者中甲苯磺丁脲的药代动力学，并定量地合理化了其已知的药物相互作用。我们的结果为 OAT2 介导的肝摄取在甲苯磺丁脲药代动力学中的作用提供了一线证据，并暗示需要在这方面进行更多的临床研究。
