Mass spectrometric and NMR characterization of metabolites of roxifiban, a potent and selective antagonist of the platelet glycoprotein IIb/IIIa receptor.
1. The methyl ester prodrug roxifiban is an orally active, potent and selective antagonist of the platelet glycoprotein GPIIb/IIIa receptor and is being developed for the prevention and treatment of arterial thrombosis. 2. Roxifiban was rapidly hydrolyzed to the zwitterion XV459 in vivo and by liver slices from the rat, mouse and human and by intestinal cores from dog. XV459 was metabolized to only a small extent in vitro and in vivo. 3. Studies with rat and dog given radiolabelled roxifiban showed limited oral absorption with the majority of the radiolabel being excreted in faeces. After i.v. doses of 14C-roxifiban, most of the radioactivity was recovered in the urine of rat whereas the dog excreted significant amounts of radioactivity in bile and urine. 4. XV459 could be metabolized extrahepatically by dog gut flora to produce an isoxazoline ring-opened metabolite. In vitro hepatic metabolism of XV459 was mainly by hydroxylation at the prochiral and chiral centres of the isoxazoline ring. These hydroxylated metabolites were not detected in the urine and plasma of human volunteers administered roxifiban. 5. Initial LC/MS identification of metabolites was achieved by dosing the rat with an equimolar mixture of d0:d4 roxifiban and detecting isotopic clusters of pseudomolecular ions. Unequivocal characterization of these metabolites was achieved by LC/MS, LC/NMR and high-field NMR techniques using synthetic standards of the metabolites. 6. The synthesis of one hydroxylated metabolite enabled the assignment of the correct stereochemistry of the substituted hydroxyl group on the isoxazoline ring.
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Drug Metabolism and Pharmacokinetics Section, DuPont Pharmaceuticals Company, Stine-Haskell Research Center, PO Box 30, Elkton Road, Newark, DE 19714, USA. abdul.mutlib@dupontpharma.com
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D000578:Amidines / Q000378:metabolism* / Q000493:pharmacokinetics* / Q000652:urine; D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D002317:Cardiovascular Agents / Q000378:metabolism* / Q000493:pharmacokinetics* / Q000652:urine; D002851:Chromatography, High Pressure Liquid; D004285:Dogs; D005243:Feces; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007555:Isoxazoles / Q000378:metabolism* / Q000493:pharmacokinetics* / Q000494:pharmacology / Q000652:urine; D008099:Liver / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D051379:Mice; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000037:antagonists & inhibitors* / Q000737:chemistry*; D051381:Rats; D013927:Thrombosis / Q000188:drug therapy*
D000578:Amidines; D000596:Amino Acids; D002317:Cardiovascular Agents; D007555:Isoxazoles; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; C104284:XV 459; C118235:roxifiban