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Drug Metabolism and Disposition Fast Forward
First published on July 24, 2008; DOI: 10.1124/dmd.108.022277

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Received for publication May 9, 2008.
Revised July 18, 2008.
Accepted for publication July 21, 2008.

Metabolism, Pharmacokinetics and Excretion of a Cholesteryl Ester Transfer Protein Inhibitor, Torcetrapib, in Rats, Monkeys, and Mice: Characterization of Unusual and Novel Metabolites by High Resolution LC-MS/MS and 1H NMR

Chandra Prakash 1*, Chen Weichao 1, Michelle Rossulek 1, Kim Johnson 1, Chenghong Zhang 2, Thomas O'Connell 2, Michael Potchoiba 1, Deepak Dalvie 1

1 Pfizer 2 pfizer

* Address correspondence to: E-mail: chandra.prakash{at}pfizer.com

Abstract

The disposition of torcetrapib, a CETP inhibitor, was studied in rats, monkeys and mice following oral administration of a single dose of [14C]torcetrapib. Total mean recoveries of the radiocarbon were 90.9, 93.4 and 86.8% from mice, rats, and monkeys, respectively. Excretion of radioactivity was rapid and nearly complete within 48 h after dosing with majority excreted in the feces in all species. Torcetrapib was not detected in the urine and/or bile across species suggesting that it is primarily cleared by metabolism in these species. More than twenty eight metabolites were identified in all species, and were products of oxidation and conjugation pathways. The primary metabolic pathways of torcetrapib involved hydrolysis of the carbamate ester (M2) and the oxidation of the ethyl moieties. M2 was subsequently metabolized in parallel by oxidative cleavage to novel and unusual quinoline metabolites (M3, M4, M5, M9 and M17), bis trifluuromethyl benzoic acid (M1), and 3,5 bis(trifluoromethyl)phenyl)-(methoxycarbonyl)methanesulfonic acid (M28). The structures of several metabolites were established by high resolution LC-MS/MS and 1H NMR. The major circulating and excretory metabolites in mice, rats and monkeys were species-dependent, however, several common metabolites were observed in more than one species. In addition to parent torcetrapib, M1, M3, and M4 in rats, M4 and M17 in mice, and M3 and M8 in monkeys were detected as the major circulating metabolites. A mechanism for the formation of an unusual metabolite M28 has been proposed.


Key words: drug development, drug disposition, mass spectrometry, metabolite identification


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D. Dalvie, W. Chen, C. Zhang, A. D. Vaz, T. A. Smolarek, L. M. Cox, J. Lin, and R. S. Obach
Pharmacokinetics, Metabolism, and Excretion of Torcetrapib, a Cholesteryl Ester Transfer Protein Inhibitor, in Humans
Drug Metab. Dispos., November 1, 2008; 36(11): 2185 - 2198.
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