Uchida T, Watanabe T, Van Hoogdalem E J, Higuchi S
Drug Metabolism Department, Yamanouchi Pharmaceutical Co. Ltd, Tokyo, Japan.
J Pharm Pharmacol. 1996 Oct;48(10):1049-56. doi: 10.1111/j.2042-7158.1996.tb05898.x.
Because YM17E (1,3-bis[[1-cycloheptyl-3-(p-dimethylaminophenyl) ureido]methyl]benzene dihydrochloride) inhibits acyl coenzyme A:cholesterol acyltransferase (ACAT) it has potential application in the treatment of hypercholesterolaemia. In man and animals YM17E is extensively metabolized, via N-demethylation, to five active metabolites (M1, M2-a, M2-b, M3 and M4). The main objectives of this study were to examine inhibition of YM17E metabolism by the products and identify the cytochrome P450 isoforms in liver microsomes which catalyse in-vitro YM17E metabolism in man. In microsomes in man N-demethylation of YM17E to M1 occurred enzymatically; for up to 45 s the rate was linearly proportional to the microsomal protein concentration. This reaction was inhibited by metabolites M2-a, M2-b, M3 and M4. Further, N-demethylation of [14C]-YM17E was also inhibited by its product, M1. These results showed that primary metabolism of YM17E was inhibited by its products, and supported the finding that the non-linear increase in plasma concentration of the parent drug and metabolites observed in an in-vivo study was due to inhibition by these products. Metabolic activity in microsomes from ten individual human livers demonstrated that YM17E N-demethylase activity correlated closely with testosterone 6 beta-hydroxylase activity. When cytochrome P450 isozyme-specific substrates and chemical inhibitors were used to inhibit YM17E N-demethylase activity, CYP3A-specific substrate and inhibitors such as nifedipine, ketoconazole and triacetyloleandomycin strongly inhibited this activity, whereas CYP1A-specific substrate or inhibitor, ethoxyresorufin and alpha-naphthoflavone, inhibited weakly. Other CYP inhibitors, in contrast, had few or no effects. An inhibition study using anti-rat CYP1A1, CYP2B1, CYP2C11, CYP2E1 and CYP3A2 antibodies demonstrated that only anti-rat CYP3A2 antibody inhibited YM17E metabolism, to 40% of control level, with no other antibodies showing an inhibitory effect. Of seven cDNA-expressed P450 isoforms in man (CYP1A1, CYP1A2, CYP2A6, CYP2B6, CYP2D6, CYP2E1 and CYP3A4), CYP3A4, CYP2D6 and CYP1A2 isozyme exhibited substantial catalytic activity of N-demethylation of YM17E. These results indicate the predominant role of CYP3A4 in liver metabolism of YM17E in man.
由于YM17E（1,3 - 双[[1 - 环庚基 - 3 - （对二甲氨基苯基）脲基]甲基]苯二盐酸盐）可抑制酰基辅酶A：胆固醇酰基转移酶（ACAT），因此它在高胆固醇血症的治疗中具有潜在应用价值。在人和动物体内，YM17E通过N - 去甲基化广泛代谢为五种活性代谢物（M1、M2 - a、M2 - b、M3和M4）。本研究的主要目的是检测产物对YM17E代谢的抑制作用，并鉴定人肝微粒体中催化体外YM17E代谢的细胞色素P450同工酶。在人微粒体中，YM17E酶促N - 去甲基化生成M1；在长达45秒的时间内，反应速率与微粒体蛋白浓度呈线性比例关系。该反应受到代谢物M2 - a、M2 - b、M3和M4的抑制。此外，[14C] - YM17E N - 去甲基化也受到其产物M1的抑制。这些结果表明YM17E的初级代谢受到其产物的抑制，并支持了体内研究中观察到的母体药物和代谢物血浆浓度非线性增加是由于这些产物抑制的这一发现。来自十个人类肝脏的微粒体的代谢活性表明，YM17E N - 去甲基酶活性与睾酮6β - 羟化酶活性密切相关。当使用细胞色素P450同工酶特异性底物和化学抑制剂来抑制YM17E N - 去甲基酶活性时，CYP3A特异性底物和抑制剂如硝苯地平、酮康唑和三乙酰竹桃霉素强烈抑制该活性，而CYP1A特异性底物或抑制剂乙氧基试卤灵和α - 萘黄酮抑制作用较弱。相比之下，其他CYP抑制剂几乎没有影响。使用抗大鼠CYP1A1、CYP2B1、CYP2C11、CYP2E1和CYP3A2抗体进行的抑制研究表明，只有抗大鼠CYP3A2抗体抑制YM17E代谢，抑制至对照水平的40%，其他抗体均未显示抑制作用。在人七种cDNA表达的P450同工酶（CYP1A1、CYP1A2、CYP2A6、CYP2B6、CYP2D6、CYP2E1和CYP3A4）中，CYP3A4、CYP2D6和CYP1A2同工酶表现出显著的YM17E N - 去甲基化催化活性。这些结果表明CYP3A4在人肝脏中YM17E代谢中起主要作用。
