Zotarolimus (ABT-578) is a sirolimus derivative that, like sirolimus and everolimus, is an inhibitor of cell growth via inhibition of the mechanistic target of rapamycin (mTOR). Zotarolimus was developed for coating coronary stents to prevent smooth muscle cell proliferation and restenosis. Albeit zotarolimus-eluting cardiovascular devices have been on the market for years, details of zotarolimus drug metabolism in humans are still unknown. Hence, it was the goal of the present study to identify zotarolimus metabolites generated by incubation with human liver microsomes. Metabolite structures were identified using high-resolution mass spectrometry, MS/ion-trap (MSn), and comparison of fragmentation patterns of the metabolites with those of zotarolimus and other known sirolimus derivatives. Kinetic parameters such as incubation time, human liver microsomal protein concentrations, and drug concentrations were optimized before scaling up the metabolism experiments. Human liver microsomes mainly hydroxylated and/or demethylated zotarolimus. The structures of the following metabolites were identified: O-demethylated metabolites: 39-O-desmethyl, 16-O-desmethyl, and 27-O-desmethyl zotarolimus; hydroxylated metabolites: hydroxy piperidine zotarolimus, 11-hydroxy, 12-hydroxy, 14-hydroxy, 23-hydroxy, 24-hydroxy, 25-hydroxy, 45/46-hydroxy, and 49-hydroxy zotarolimus; demethylated-hydroxylated metabolites: 16-O-desmethyl, 23/24-hydroxy; 39-O-desmethyl, 23/24-hydroxy; 39-O-desmethyl, 25-hydroxy zotarolimus; 39-O-desmethyl, 11-hydroxy zotarolimus; 39-O-desmethyl, hydroxy-piperidine zotarolimus; 27-O-desmethyl, 45/46-hydroxy zotarolimus; didemethylated metabolites: 16,39-O-didesmethyl zotarolimus; 16,27-O-didesmethyl zotarolimus; 27,39-O-didesmethyl zotarolimus; and dihydroxylated metabolites: 11,24-dihydroxy zotarolimus, 12,24-dihydroxy zotarolimus, and 11,47/48-dihydroxy zotarolimus. It is concluded that zotarolimus is extensively metabolized by human liver microsomes. Twenty-four of these metabolites could be structurally identified using a combination of ion-trap MSn and high-resolution mass spectrometry.

中文翻译：

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使用离子阱和高分辨率飞行时间质谱结合裂解模式分析对人肝微粒体产生的佐他莫司 (ABT-578) 代谢物进行结构鉴定

Zotarolimus (ABT-578) 是一种西罗莫司衍生物，与西罗莫司和依维莫司一样，是通过抑制雷帕霉素 (mTOR) 机制靶点来抑制细胞生长。Zotarolimus 被开发用于涂覆冠状动脉支架，以防止平滑肌细胞增殖和再狭窄。尽管佐他莫司洗脱心血管装置已上市多年，但佐他莫司药物在人体中代谢的细节仍不清楚。因此，本研究的目标是鉴定通过与人肝微粒体孵育产生的佐他莫司代谢物。使用高分辨率质谱、MS/离子阱 (MSn) 以及将代谢物的碎片模式与佐他莫司和其他已知西罗莫司衍生物的碎片模式进行比较来鉴定代谢物结构。在扩大代谢实验之前，优化了孵育时间、人肝微粒体蛋白浓度和药物浓度等动力学参数。人肝微粒体主要是羟基化和/或去甲基化的佐他莫司。鉴定了以下代谢物的结构： O-去甲基化代谢物：39-O-去甲基、16-O-去甲基和 27-O-去甲基佐他莫司；羟基化代谢物：羟基哌啶佐他莫司、11-羟基、12-羟基、14-羟基、23-羟基、24-羟基、25-羟基、45/46-羟基和49-羟基佐他莫司；去甲基化-羟基化代谢物：16-O-去甲基，23/24-羟基；39-O-去甲基，23/24-羟基；39-O-去甲基，25-羟基佐他莫司；39-O-去甲基，11-羟基佐他莫司；39-O-去甲基，羟基-哌啶佐他莫司；27-O-去甲基，45/46-羟基佐他莫司；二去甲基化代谢物：16,39-O-二去甲基佐他莫司；16,27-O-二甲基佐他莫司；27,39-O-二去甲基佐他莫司；和二羟基化代谢物：11,24-二羟基佐他莫司、12,24-二羟基佐他莫司和11,47/48-二羟基佐他莫司。结论是佐他莫司被人肝微粒体广泛代谢。结合离子阱 MSn 和高分辨率质谱分析，可以对其中 24 种代谢物进行结构鉴定。