Pharmacokinetics, Dynamics, and Metabolism , Pfizer Global Research and Development , MS 8220-2451, Groton , Connecticut 06340 , United States.
Mol Pharm. 2018 Mar 5;15(3):1284-1295. doi: 10.1021/acs.molpharmaceut.7b01108. Epub 2018 Feb 20.
Interindividual variability in warfarin dose requirement demands personalized medicine approaches to balance its therapeutic benefits (anticoagulation) and bleeding risk. Cytochrome P450 2C9 ( CYP2C9) genotype-guided warfarin dosing is recommended in the clinic, given the more potent S-warfarin is primarily metabolized by CYP2C9. However, only about 20-30% of interpatient variability in S-warfarin clearance is associated with CYP2C9 genotype. We evaluated the role of hepatic uptake in the clearance of R- and S-warfarin. Using stably transfected HEK293 cells, both enantiomers were found to be substrates of organic anion transporter (OAT)2 with a Michaelis-Menten constant ( K) of ∼7-12 μM but did not show substrate affinity for other major hepatic uptake transporters. Uptake of both enantiomers by primary human hepatocytes was saturable ( K ≈ 7-10 μM) and inhibitable by OAT2 inhibitors (e.g., ketoprofen) but not by OATP1B1/1B3 inhibitors (e.g., cyclosporine). To further evaluate the potential role of hepatic uptake in R- and S-warfarin pharmacokinetics, mechanistic modeling and simulations were conducted. A "bottom-up" PBPK model, developed assuming that OAT2-CYPs interplay, well recovered clinical pharmacokinetics, drug-drug interactions, and CYP2C9 pharmacogenomics of R- and S-warfarin. Clinical data were not available to directly verify the impact of OAT2 modulation on warfarin pharmacokinetics; however, the bottom-up PBPK model simulations suggested a proportional change in clearance of both warfarin enantiomers with inhibition of OAT2 activity. These results suggest that variable hepatic OAT2 function, in conjunction with CYP2C, may contribute to the high population variability in warfarin pharmacokinetics and possibly anticoagulation end points and thus warrant further clinical investigation.
华法林剂量需求的个体间变异性需要个性化医学方法来平衡其治疗效益（抗凝）和出血风险。鉴于更有效的 S-华法林主要由 CYP2C9 代谢，因此推荐在临床中使用细胞色素 P450 2C9（CYP2C9）基因型指导的华法林剂量。然而，S-华法林清除率的个体间变异性只有约 20-30%与 CYP2C9 基因型相关。我们评估了肝摄取在 R-和 S-华法林清除中的作用。使用稳定转染的 HEK293 细胞，发现两种对映异构体均为有机阴离子转运蛋白（OAT）2 的底物，米氏常数（K）约为 7-12 μM，但对其他主要肝摄取转运蛋白没有底物亲和力。两种对映异构体在原代人肝细胞中的摄取均为饱和性（K≈7-10 μM），可被 OAT2 抑制剂（如酮洛芬）抑制，但不能被 OATP1B1/1B3 抑制剂（如环孢素）抑制。为了进一步评估肝摄取在 R-和 S-华法林药代动力学中的潜在作用，进行了机制建模和模拟。一个“自下而上”的 PBPK 模型，假设 OAT2-CYP 相互作用，很好地恢复了 R-和 S-华法林的临床药代动力学、药物相互作用和 CYP2C9 药物基因组学。没有临床数据可以直接验证 OAT2 调节对华法林药代动力学的影响；然而，自下而上的 PBPK 模型模拟表明，OAT2 活性抑制时，两种华法林对映异构体的清除率呈比例变化。这些结果表明，可变的肝 OAT2 功能，与 CYP2C 一起，可能导致华法林药代动力学和可能的抗凝终点的人群变异性很高，因此需要进一步的临床研究。
