Abstract
Capravirine, a new non-nucleoside reverse transcriptase inhibitor, undergoes extensive oxygenation reactions, including N-oxidation, sulfoxidation, sulfonation, and hydroxylation in humans. Numerous primary (mono-oxygenated) and sequential (di-, tri-, and tetraoxygenated) metabolites of capravirine are formed via the individual or combined oxygenation pathways. In this study, cytochrome P450 enzymes responsible for the primary and sequential oxygenation reactions of capravirine in human liver microsomes were identified at the specific pathway level. The total oxygenation of capravirine is mediated predominantly (>90%) by CYP3A4 and marginally (<10%) by CYP2C8, 2C9, and 2C19 in humans. Specifically, each of the two major mono-oxygenated metabolites C23 (sulfoxide) and C26 (N-oxide), is mediated predominantly (>90%) by CYP3A4 and slightly (<10%) by CYP2C8, the minor tertiary hydroxylated metabolite C19 by CYP3A4, 2C8, and 2C19, and the minor primary hydroxylated metabolite C20 by CYP3A4, 2C8, and 2C9. However, all sequential oxygenation reactions are mediated exclusively by CYP3A4. Due to their relatively insignificant contributions of C19 and C20 to total capravirine metabolism, no attempt was made to determine relative contributions of cytochrome P450 enzymes to the formation of the two minor metabolites.
Footnotes
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Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
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doi:10.1124/dmd.106.011189.
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ABBREVIATIONS: P450, cytochrome P450; FMO, flavin-containing monooxygenase; HPLC, high-performance liquid chromatography; MS, mass spectrometry; RAM, radioactivity monitoring.
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↵1 Current affiliation: Sonus Pharmaceuticals, Bothell, WA.
- Received May 25, 2006.
- Accepted August 15, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
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