Optimized Assays for Human UDP-Glucuronosyltransferase (UGT) Activities: Altered Alamethicin Concentration and Utility to Screen for UGT Inhibitors
作者:Robert L. Walsky、Jonathan N. Bauman、Karine Bourcier、Georgina Giddens、Kimberly Lapham、Andre Negahban、Tim F. Ryder、R. Scott Obach、Ruth Hyland、Theunis C. Goosen
DOI:10.1124/dmd.111.043117
日期:2012.5
The measurement of the effect of new chemical entities on human UDP-glucuronosyltransferase (UGT) marker activities using in vitro experimentation represents an important experimental approach in drug development to guide clinical drug-interaction study designs or support claims that no in vivo interaction will occur. Selective high-performance liquid chromatography-tandem mass spectrometry functional assays of authentic glucuronides for five major hepatic UGT probe substrates were developed: β-estradiol-3-glucuronide (UGT1A1), trifluoperazine- N -glucuronide (UGT1A4), 5-hydroxytryptophol- O -glucuronide (UGT1A6), propofol- O -glucuronide (UGT1A9), and zidovudine-5′-glucuronide (UGT2B7). High analytical sensitivity permitted characterization of enzyme kinetic parameters at low human liver microsomal and recombinant UGT protein concentration (0.025 mg/ml), which led to a new recommended optimal universal alamethicin activation concentration of 10 μg/ml for microsomes. Alamethicin was not required for recombinant UGT incubations. Apparent enzyme kinetic parameters, particularly for UGT1A1 and UGT1A4, were affected by nonspecific binding. Unbound intrinsic clearance for UGT1A9 and UGT2B7 increased significantly after addition of 2% bovine serum albumin, with minimal changes for UGT1A1, UGT1A4, and UGT1A6. Eleven potential UGT and cytochrome P450 inhibitors were evaluated as UGT inhibitors, resulting in observation of nonselective UGT inhibition by chrysin, mefenamic acid, silibinin, tangeretin, ketoconazole, itraconazole, ritonavir, and verapamil. The pan-cytochrome P450 inhibitor, 1-aminobenzotriazole, minimally inhibited UGT activities and may be useful in reaction phenotyping of mixed UGT and cytochrome P450 substrates. These methods should prove useful in the routine assessments of the potential for new drug candidates to elicit pharmacokinetic drug interactions via inhibition of human UGT activities and the identification of UGT enzyme-selective chemical inhibitors.
利用体外实验测量新化学实体对人类 UDP-葡萄糖醛酸转移酶(UGT)标记活性的影响是药物开发中的一种重要实验方法,可用于指导临床药物相互作用研究设计或支持不会发生体内相互作用的说法。我们开发了针对五种主要肝脏 UGT 探针底物的真品葡萄糖醛酸的选择性高效液相色谱-串联质谱功能测定:β-雌二醇-3-葡萄糖醛酸苷(UGT1A1)、三氟拉嗪-N-葡萄糖醛酸苷(UGT1A4)、5-羟基色氨醇-O-葡萄糖醛酸苷(UGT1A6)、丙泊酚-O-葡萄糖醛酸苷(UGT1A9)和齐多夫定-5′-葡萄糖醛酸苷(UGT2B7)。由于分析灵敏度高,因此可以在较低的人肝微粒体和重组 UGT 蛋白浓度(0.025 毫克/毫升)下鉴定酶动力学参数,从而推荐了新的最佳阿拉美辛活化微粒体的通用浓度为 10 微克/毫升。重组 UGT 培养不需要氨基甲酸乙酯。表观酶动力学参数,尤其是 UGT1A1 和 UGT1A4,受到非特异性结合的影响。加入 2% 的牛血清白蛋白后,UGT1A9 和 UGT2B7 的非结合内在清除率显著增加,而 UGT1A1、UGT1A4 和 UGT1A6 的变化极小。将 11 种潜在的 UGT 和细胞色素 P450 抑制剂作为 UGT 抑制剂进行了评估,结果观察到金丝桃素、甲氰咪胍、西利宾、坦格列汀、酮康唑、伊曲康唑、利托那韦和维拉帕米对 UGT 有非选择性抑制作用。泛细胞色素 P450 抑制剂 1-aminobenzotriazole 对 UGT 活性的抑制作用很小,可用于 UGT 和细胞色素 P450 混合底物的反应表型分析。这些方法将有助于对候选新药通过抑制人体 UGT 活性引起药代动力学药物相互作用的可能性进行常规评估,并有助于鉴定 UGT 酶选择性化学抑制剂。