title: In vitro metabolic study of temsirolimus: preparation, isolation, and identification of the metabolites.
abstract: The in vitro metabolism of temsirolimus, (rapamycin-42-[2,2-bis-(hydroxymethyl)]-propionate), an antineoplastic agent, was studied using human liver microsomes as well as recombinant human cytochrome P450s, namely CYP3A4, 1A2, 2A6, 2C8, 2C9, 2C19, and 2E1. Fifteen metabolites were detected by liquid chromatography (LC)-tandem mass spectrometry (MS/MS or MS/MS/MS). CYP3A4 was identified as the main enzyme responsible for the metabolism of the compound. Incubation of temsirolimus with recombinant CYP3A4 produced most of the metabolites detected from incubation with human liver microsomes, which was used for large-scale preparation of the metabolites. By silica gel chromatography followed by semipreparative reverse-phase high-performance liquid chromatography, individual metabolites were separated and purified for structural elucidation and bioactivity studies. The minor metabolites (peaks 1-7) were identified as hydroxylated or desmethylated macrolide ring-opened temsirolimus derivatives by both positive and negative mass spectrometry (MS) and MS/MS spectroscopic methods. Because these compounds were unstable and only present in trace amounts, no further investigations were conducted. Six major metabolites were identified as 36-hydroxyl temsirolimus (M8), 35-hydroxyl temsirolimus (M9), 11-hydroxyl temsirolimus with an opened hemiketal ring (M10 and M11), N- oxide temsirolimus (M12), and 32-O-desmethyl temsirolimus (M13) using combined LC-MS, MS/MS, MS/MS/MS, and NMR techniques. Compared with the parent compound, these metabolites showed dramatically decreased activity against LNCaP cellular proliferation.
authors.affiliation: Chemical and Pharmaceutical Development, Wyeth Research, Building 250/229, 401 N. Middletown Rd., Pearl River, NY 10965, USA. caip@wyeth.com
authors.forename: Ping
authors.initials: P
authors.lastname: Cai
authors.forename: Rushung
authors.initials: R
authors.lastname: Tsao
authors.forename: Mark E
authors.initials: ME
authors.lastname: Ruppen
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000378:metabolism* / Q000493:pharmacokinetics / Q000494:pharmacology; D001711:Biotransformation; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008862:Microsomes, Liver / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D020123:Sirolimus / Q000031:analogs & derivatives* / Q000378:metabolism / Q000493:pharmacokinetics / Q000494:pharmacology; D021241:Spectrometry, Mass, Electrospray Ionization; D013329:Structure-Activity Relationship
chemical_list: D000903:Antibiotics, Antineoplastic; D007202:Indicators and Reagents; D011994:Recombinant Proteins; C401859:temsirolimus; D003577:Cytochrome P-450 Enzyme System; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D020123:Sirolimus