title: Assessment of the in-vivo stereochemical integrity of aprepitant based on the analysis of human plasma samples via high-performance liquid chromatography with mass spectrometric detection.
abstract: Achiral and chiral liquid chromatographic methods utilizing mass spectrometric detection were developed to investigate the possibility of inversion of configuration at any or all of the chiral centers of the neurokinin-1 (NK-1) receptor antagonist, aprepitant (5-[[2(R)-[1(R)-(3,5-bistrifluoromethyl phenyl)ethoxy]-3(S)-(4-fluorophenyl)morpholin-4-yl]methyl]-2,4-dihydro-[1,2,4]triazol-3-one), in-vivo, following administration of the compound to man. A structure such as aprepitant, that contains three chiral centers, may exist in eight stereochemical forms or, more specifically, as four diastereoisomeric pairs of enantiomers. The four diastereoisomers were separated from each other using a ProntoSil C18 AQ HPLC column (4.6 x 100 mm, 3 microm particles) with a mobile phase composed of acetonitrile--water (47:53, v/v%). Detection was via a single quadrupole mass spectrometer that was connected to the HPLC system via an APCI interface. Analysis of post-dose plasma samples under these conditions indicated that only aprepitant and or its enantiomer were present following oral administration of the drug. Aprepitant and its enantiomer were separated using a Chiralcel OD-H HPLC column with a mobile phase composed of hexane-isopropanol (80:20, v/v%); tandem mass spectrometric detection using an APCI interface was employed. Post-dose plasma samples analyzed using the Chiracel column were found to contain only aprepitant. The results of these experiments confirm that the products of inversion of configuration at any or all of the three chiral centers of aprepitant are not detectable in human plasma samples obtained following the administration of the drug.
authors.affiliation: Merck Research Laboratories, Department of Drug Metabolism, West Point, PA 19486, USA. walter-kline@merck.com
authors.forename: W F
authors.initials: WF
authors.lastname: Kline
authors.forename: E J
authors.initials: EJ
authors.lastname: Woolf
authors.forename: B K
authors.initials: BK
authors.lastname: Matuszewski
mesh_terms: D000077608:Aprepitant; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods*; D008968:Molecular Conformation; D009025:Morpholines / Q000097:blood* / Q000737:chemistry*; D064729:Neurokinin-1 Receptor Antagonists; D013237:Stereoisomerism
chemical_list: D009025:Morpholines; D064729:Neurokinin-1 Receptor Antagonists; D000077608:Aprepitant