RT Journal Article
SR Electronic
T1 PROTEIN COVALENT BINDING OF MAXIPOST THROUGH A CYTOCHROME P450-MEDIATED ORTHO-QUINONE METHIDE INTERMEDIATE IN RATS
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 837
OP 845
DO 10.1124/dmd.31.7.837
VO 31
IS 7
A1 Donglu Zhang
A1 Marc Ogan
A1 Richard Gedamke
A1 Vikram Roongta
A1 Renke Dai
A1 Mingshe Zhu
A1 J. Kent Rinehart
A1 Lewis Klunk
A1 James Mitroka
YR 2003
UL http://dmd.aspetjournals.org/content/31/7/837.abstract
AB (3S)-(+)-(5-Chloro-2-methoxyphenyl)-1,3-dihydro-3-fluoro-6-(trifluoromethyl)-2H-indole-2-one) (MaxiPost, BMS-204352) is a potent and specific opener for maxi-K channels and has potential to prevent and treat ischemic stroke. Following single intravenous doses of [14C]BMS-204352 to rats, only 10 to 12% of radioactivity was extractable from plasma with organic solvents. The unextractable radioactivity remained associated with the proteins (mostly albumin) after SDS-polyacrylamide gel eletrophoresis or dialysis. Following acid hydrolysis in 6 M HCl for 24 h at 110°C from plasma proteins collected from nine rats dosed with [14C]BMS-204352, one major radioactive product was isolated and identified as a lysine-adduct of des-fluoro des-O-methyl BMS-204352 by liquid chromatography/mass spectrometry and NMR analyses as well as by comparison with the synthetic analog, lysine-adduct of des-fluoro BMS-204352 (BMS-349821). The covalent binding of BMS-204352 results from the displacement of the ring-fluorine atom of des-O-methyl BMS-204352 with the ϵ-amino group of a lysine residue. Microsomal incubations of [14C]BMS-204352 resulted in low levels of covalent binding of radioactivity to proteins. This in vitro covalent binding required cytochrome P450-reductase cofactor NADPH and was attenuated by glutathione. P4503A inhibitors ketoconazole and troleadomycin selectively prevented the covalent binding in vitro. Based on these observations, a two-step bioactivation process for the protein covalent binding of BMS-204352 was postulated: 1) P4503A-mediated O-demethylation leading to spontaneous release of HF and the formation of an ortho-quinone methide reactive metabolite and 2) nucleophilic addition of the ϵ-amino group of protein lysine residue(s) in protein to form des-fluoro des-O-methyl BMS-204352 lysine adduct. The American Society for Pharmacology and Experimental Therapeutics