Bristol-Myers Squibb Molecular Sciences & Candidate Optimization, Wallingford, Connecticut, USA.
Drug Metab Dispos. 2011 Dec;39(12):2421-30. doi: 10.1124/dmd.111.041947. Epub 2011 Sep 12.
In previous studies, gemfibrozil acyl-β-glucuronide, but not gemfibrozil, was found to be a mechanism-based inhibitor of cytochrome P450 2C8. To better understand whether this inhibition is specific for gemfibrozil acyl-β-glucuronide or whether other glucuronide conjugates are potential substrates for inhibition of this enzyme, we evaluated several pharmaceutical compounds (as their acyl glucuronides) as direct-acting and metabolism-dependent inhibitors of CYP2C8 in human liver microsomes. Of 11 compounds that were evaluated as their acyl glucuronide conjugates, only gemfibrozil acyl-β-glucuronide exhibited mechanism-based inhibition, indicating that CYP2C8 mechanism-based inhibition is very specific to certain glucuronide conjugates. Structural analogs of gemfibrozil were synthesized, and their glucuronide conjugates were prepared to further examine the mechanism of inhibition. When the aromatic methyl groups on the gemfibrozil moiety were substituted with trifluoromethyls, the resulting glucuronide conjugate was a weaker inhibitor of CYP2C8 and mechanism-based inhibition was abolished. However, the glucuronide conjugates of monomethyl gemfibrozil analogs were mechanism-based inhibitors of CYP2C8, although not as potent as gemfibrozil acyl-β-glucuronide itself. The ortho-monomethyl analog was a more potent inhibitor than the meta-monomethyl analog, indicating that CYP2C8 favors the ortho position for oxidation and potential inhibition. Molecular modeling of gemfibrozil acyl-β-glucuronide in the CYP2C8 active site is consistent with the ortho-methyl position being the favored site of covalent attachment to the heme. Moreover, hydrogen bonding to four residues (Ser100, Ser103, Gln214, and Asn217) is implicated.
在之前的研究中，发现吉非贝齐酰基-β-葡糖苷酸而不是吉非贝齐本身是细胞色素 P450 2C8 的一种基于机制的抑制剂。为了更好地了解这种抑制作用是否特定于吉非贝齐酰基-β-葡糖苷酸，或者其他葡糖苷酸缀合物是否是抑制这种酶的潜在底物，我们评估了几种医药化合物（作为它们的酰基葡糖苷酸）作为人肝微粒体中 CYP2C8 的直接作用和代谢依赖性抑制剂。在所评估的 11 种化合物中，只有吉非贝齐酰基-β-葡糖苷酸表现出基于机制的抑制作用，表明 CYP2C8 基于机制的抑制作用非常特定于某些葡糖苷酸缀合物。合成了吉非贝齐的结构类似物，并制备了它们的葡糖苷酸缀合物，以进一步研究抑制作用的机制。当吉非贝齐部分的芳基甲基被三氟甲基取代时，所得的葡糖苷酸缀合物对 CYP2C8 的抑制作用较弱，并且基于机制的抑制作用被消除。然而，吉非贝齐单甲基类似物的葡糖苷酸缀合物是 CYP2C8 的基于机制的抑制剂，尽管不如吉非贝齐酰基-β-葡糖苷酸本身有效。邻位单甲基类似物比间位单甲基类似物更有效，表明 CYP2C8 有利于氧化和潜在抑制的邻位。吉非贝齐酰基-β-葡糖苷酸在 CYP2C8 活性位点的分子建模与共价附着到血红素的邻位甲基位置一致。此外，与四个残基（Ser100、Ser103、Gln214 和 Asn217）的氢键有关。
