Abstract
Bevirimat [BVM, PA-457, 3-O-(3′,3′-dimethylsuccinyl)-betulinic acid], a new anti-human immunodeficiency virus drug candidate, is metabolized to two monoglucuronides [mono-BVMG (I) and mono-BVMG (II)] and one diglucuronide (di-BVMG) both in vivo and in vitro. UDP-glucuronosyltransferase (UGT) reaction screening, enzyme kinetics, and species differences for the glucuronidation of BVM in vitro were investigated with pooled human liver microsomes (HLMs) and human intestinal microsomes (HIMs), animal liver microsomes, and 12 recombinant human UGT isoforms. Glucuronidation of BVM with HLMs predominantly involved the formation of mono-BVMG (I) (Vmax = 61 pmol/min/mg protein, Km = 27 μM) and mono-BVMG (II) (Vmax = 48 pmol/min/mg protein, Km = 16 μM). Di-BVMG was also observed but was a minor metabolite. HIMs mainly revealed glucuronidation to form mono-BVMG (II) (Vmax = 90 pmol/min/mg of protein, Km = 8.3 μM). UGT1A3 predominantly formed mono-BVMG (I) (Vmax = 65 pmol/min/mg of protein, Km = 13 μM), whereas UGT1A4 is a less active isoform (Vmax = 1.8 pmol/min/mg of protein, Km = 5.6 μM). UGT2B7 was involved in the formation of both mono-BVMG (I) (Vmax = 6.1 pmol/min/mg of protein, Km = 6.0 μM) and mono-BVMG (II) (Vmax = 6.5 pmol/min/mg of protein, Km = 7.8 μM). Among the animal liver microsomes examined, all species (rat, mouse, dog, and marmoset) demonstrated conjugation to form both mono-BVMG (I) and mono-BVMG (II), with dog liver microsomes exhibiting a higher formation rate for mono-BVMG (I), whereas marmoset liver microsomes showed a higher formation rate for mono-BVMG (II). The data suggest a primary role of UGT1A3 for the glucuronidation of BVM.
Footnotes
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This research was supported by a contract from Panacos Pharmaceuticals (to P.C.S.) and, in part, by National Institutes of Health Grant AI33066 from National Institute of Allergy and Infectious Diseases (to K.H.L.).
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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.106.012815.
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ABBREVIATIONS: UGT, UDP-glucuronosyltransferase; NSAID, nonsteroidal anti-inflammatory drug; BVM, bevirimat, 3-O-(3′,3′-dimethylsuccinyl)-betulinic acid; HIV, human immunodeficiency virus; LC, liquid chromatography; ESI, electrospray ionization; MS, mass spectrometry; BVMG, glucuronide of BVM; HLM, human liver microsome; HIM, human intestinal microsome; DSD, 3-O-(3′,3′-dimethylsuccinyl)-dihydrobetulinic acid; UDPGA, uridine 5′-diphosphoglucuronic acid; d-SL, d-saccharic acid 1,4-lactone; PMSF, phenylmethylsulfonyl fluoride; TFA, trifluoroacetic acid; AZT, zidovudine; TFP, trifluoperazine; 7-HFC, 7-hydroxy-4-trifluoromethylcoumarin; 7-HFCG, 4-trifluoromethyl-7-hydroxycoumarin glucuronide; RLM, rat liver microsome; MLM, mouse liver microsome; DLM, dog liver microsome; MMLM, marmoset liver microsome; RIM, rat intestinal microsome; ACN, acetonitrile; HPLC, high-performance liquid chromatography; SPE, solid-phase extraction; HAc, glacial acetic acid; TFPG, trifluoperazine glucuronide.
- Received September 8, 2006.
- Accepted December 5, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
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