Kammerer Bernd, Scheible Holger, Albrecht Wolfgang, Gleiter Christoph H, Laufer Stefan
University Hospital Tübingen, Department of Clinical Pharmacology, Tübingen, Germany.
Drug Metab Dispos. 2007 Jun;35(6):875-83. doi: 10.1124/dmd.106.013409. Epub 2007 Mar 7.
The p38 mitogen-activated protein kinase (MAPK) is a key mediator in cytokine-induced signaling events that are activated in response to a variety of extracellular stimuli such as stress factors, apoptosis, and proliferation. Therefore, the MAPK family plays an integral role in disease states including oncogenesis, autoimmune diseases, and inflammatory processes. Inhibition of these protein kinases represents an attractive strategy for therapeutic intervention. In particular, one class of p38 MAP kinase inhibitors, the pyridinyl imidazole derivatives, is intensely investigated by several industrial groups, but so far no studies concerning the metabolism of these structurally related substances seem to be available. The objective of our examinations was the preclinical characterization of ML3403, {4-[5-(4-fluorophenyl)-2-methylsulfanyl-3H-imidazol-4-yl]-pyridin-2-yl}-(1-phenylethyl)-amine, a potent inhibitor of p38 MAP kinase, comprising the basic pyridinyl imidazole structure. In human hepatic microsomal incubations, the sulfoxidation to ML3603 ({4-[5-(4-fluorophenyl)-2-methylsulfinyl-3H-imidazol-4-yl]-pyridin-2-yl}-(1-phenylethyl)-amine) and M-sulfone ({4-[5-(4-fluorophenyl)-2-methylsulfonyl-3H-imidazol-4-yl]-pyridin-2-yl}-(1-phenylethyl)-amine) was found to be the predominant metabolic transformation. In addition, oxidative removal of the phenylethyl moiety, pyridine N-oxidation, and hydroxylation reactions were observed. Incubations were carried out with hepatic microsomes from various species and with recombinant human cytochrome P450 isoenzymes, showing that CYP1A2, CYP2C19, CYP2D6, and CYP3A4 are the prominent enzymes in the metabolism of ML3403. Michaelis-Menten kinetics of ML3603 formation by these recombinant isoenzymes showed that CYP3A4 plays a pivotal role in the sulfoxidation reaction. In addition, pharmacokinetics of ML3403 were evaluated in male and female Wistar rats after oral gavage, showing a fast and high conversion to its active sulfoxide metabolite ML3603. A remarkable gender-specific difference in the systemic exposure to ML3403 and ML3603 was found in rats. No gender-specific difference was detected in incubations with human liver microsomes.
p38丝裂原活化蛋白激酶（MAPK）是细胞因子诱导信号转导事件中的关键介质，这些信号转导事件在响应多种细胞外刺激（如应激因子、细胞凋亡和增殖）时被激活。因此，MAPK家族在包括肿瘤发生、自身免疫性疾病和炎症过程在内的疾病状态中起着不可或缺的作用。抑制这些蛋白激酶是一种有吸引力的治疗干预策略。特别是，一类p38 MAP激酶抑制剂，即吡啶基咪唑衍生物，正受到多个工业集团的深入研究，但迄今为止，似乎尚无关于这些结构相关物质代谢的研究。我们研究的目的是对ML3403进行临床前表征，ML3403即{4-[5-(4-氟苯基)-2-甲基硫烷基-3H-咪唑-4-基]-吡啶-2-基}-(1-苯乙基)-胺，是一种有效的p38 MAP激酶抑制剂，具有基本的吡啶基咪唑结构。在人肝微粒体孵育实验中，发现其主要代谢转化为氧化成ML3603（{4-[5-(4-氟苯基)-2-甲基亚磺酰基-3H-咪唑-4-基]-吡啶-2-基}-(1-苯乙基)-胺）和M-砜（{4-[5-(4-氟苯基)-2-甲基磺酰基-3H-咪唑-4-基]-吡啶-2-基}-(1-苯乙基)-胺）。此外，还观察到苯乙基部分的氧化去除、吡啶N-氧化和羟基化反应。用来自不同物种的肝微粒体和重组人细胞色素P450同工酶进行孵育实验，结果表明CYP1A2、CYP2C19、CYP2D6和CYP3A4是ML3403代谢过程中的主要酶。这些重组同工酶催化生成ML3603的米氏动力学表明，CYP3A4在氧化反应中起关键作用。此外，在雄性和雌性Wistar大鼠经口灌胃后评估了ML3403的药代动力学，结果显示其快速且高效地转化为活性亚砜代谢物ML3603。在大鼠中发现ML3403和ML3603的全身暴露存在显著的性别差异。在用人肝微粒体进行的孵育实验中未检测到性别差异。
