Supplementary figures from “Metabolite Identification, Tissue Distribution, Excretion and Preclinical Pharmacokinetic Studies of ET-26-HCl, a New Analog of Etomidate”

ET-26-HCl, a novel anaesthetic agent with promising pharmacological properties, lacks extensive studies on pharmacokinetics and disposition <i>in vitro</i> and <i>in vivo</i>. In this study, we investigated the metabolic stability, metabolite production and plasma protein binding (PPB) of ET-26-HCl along with its tissue distribution, excretion and pharmacokinetics in animals after intravenous administration. Ultra-high performance liquid chromatography–tandem quadrupole time-of-flight mass spectrometry identified a total of eight new metabolites after ET-26-HCl biotransformation in liver microsomes from different species. A hypothetical cytochrome P450-metabolic pathway including dehydrogenation, hydroxylation and demethylation was proposed. The PPB rate was highest in mouse and lowest in human. After intravenous administration, ET-26-HCl distributed rapidly to all tissues in rats and beagle dogs, with the highest concentrations in fat and liver. High concentrations of ET-26-acid, a major hydroxylation metabolite of ET-26-HCl, were found in liver, plasma and kidney. Almost complete clearance of ET-26-HCl from plasma occurred within 4 h after administration. Only a small fraction of the parent compound and its acid form were excreted via the urine and faeces. Taken together, the results added to a better understanding of the metabolic and pharmacokinetic properties of ET-26-HCl, which may contribute to the further development of this drug.

ET-26-HCl作为一种具有良好应用前景的新型麻醉剂，目前尚缺乏针对其体外（in vitro）与体内（in vivo）药代动力学及体内处置过程的系统性研究。本研究针对ET-26-HCl的代谢稳定性、代谢物生成情况及血浆蛋白结合（plasma protein binding, PPB）率展开考察，同时探究了该药物经静脉给药后在动物体内的组织分布、排泄行为与药代动力学特征。采用超高效液相色谱-串联四极杆飞行时间质谱（ultra-high performance liquid chromatography–tandem quadrupole time-of-flight mass spectrometry），在不同物种的肝微粒体中对ET-26-HCl进行生物转化后，共鉴定出8种新型代谢产物。本研究提出了一条涵盖脱氢、羟化与脱甲基反应的细胞色素P450（cytochrome P450）介导的潜在代谢通路。血浆蛋白结合率在小鼠体内最高，人类体内最低。经静脉给药后，ET-26-HCl可快速分布于大鼠与比格犬的全身各组织，其中脂肪与肝脏中的药物浓度最高。作为ET-26-HCl的主要羟化代谢物，ET-26-酸在肝脏、血浆与肾脏中均呈现高浓度水平。给药后4小时内，血浆中的ET-26-HCl几乎被完全清除。仅有少量原形药物及其酸代谢产物通过尿液与粪便排出体外。综上，本研究结果深化了对ET-26-HCl代谢与药代动力学特性的认知，可为该药物的后续研发提供重要参考。