Abstract
Omapatrilat, a potent vasopeptidase inhibitor, is currently under development for the treatment of hypertension and congestive heart failure. This study describes the plasma profile along with isolation and identification of urinary metabolites of omapatrilat from subjects dosed orally with 50 mg of [14C]omapatrilat. Only a portion of the radioactivity in plasma was unextractable (40–43%). Prominent metabolites identified in plasma were S-methyl omapatrilat, acyl glucuronide of S-methyl omapatrilat, and S-methyl (S)-2-thio-3-phenylpropionic acid. Omapatrilat accounted for less than 3% of the radioactivity. However, after dithiothreitol reduction all of the radioactivity was extractable and was characterized to be omapatrilat and its hydrolysis product (S)-2-thio-3-phenylpropionic acid, both apparently bound to proteins via reversible disulfide bonds. Urinary profile of radioactivity showed no parent compound but the presence of several metabolites that can be grouped into three categories. 1) Three metabolites, accounting for 56% of the urinary radioactivity, resulted from the hydrolysis of the exocyclic amide bond of omapatrilat. Two metabolites were diastereomers ofS-methyl sulfoxide of (S)-2-thio-3-phenylpropionic acid, and the third was the acyl glucuronide of S-methyl (S)-2-thio-3-phenylpropionic acid. 2) One disulfide, identified as the l-cysteine mixed disulfide of omapatrilat, accounted for 8% of the radioactivity in the urine. 3) Five metabolites, derived from omapatrilat, accounted for 30% of the radioactivity in the urine. Two of these metabolites were mixtures of diastereomers of S-methyl sulfoxide of omapatrilat and the third was the S-methyl omapatrilat ring sulfoxide. The other two metabolites were S-methyl omapatrilat and its acyl glucuronide. These results indicate that omapatrilat undergoes extensive metabolism in humans.
Footnotes
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Send reprint requests to: Ramaswamy A. Iyer, Ph.D., Department of Metabolism and Pharmacokinetics, Bristol-Myers Squibb Pharmaceutical Research Institute, P.O. Box 4000, Mail Stop F13-01, Princeton, NJ 08543-4000. E-mail: ramaswamy.iyer{at}bms.com
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↵1 Part of this work was presented as a poster at the 1999 International Society for Study of Xenobiotics (ISSX) meeting, Nashville, TN.
- Abbreviations used are::
- ACE
- angiotensin-converting enzyme
- NEP
- neutral endopeptidase
- DTT
- dithiothreitol
- HPLC
- high-performance liquid chromatography
- LC/MS
- liquid chromatography/mass spectrometry
- TLC
- thin-layer chromatography
- NMR
- nuclear magnetic resonance
- COSY
- correlation spectroscopy
- ESI
- electrospray ionization
- LC/MS2
- LC/MS/MS
- LC/MS3
- LC/MS/MS/MS
- Received April 19, 2000.
- Accepted October 3, 2000.
- The American Society for Pharmacology and Experimental Therapeutics
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