Characterization of metabolites of a NK1 receptor antagonist, CJ-11,972, in human liver microsomes and recombinant human CYP isoforms by liquid chromatography/tandem mass spectrometry.
The in vitro metabolism of CJ-11,972, (2-benzhydryl-1-aza-bicyclo[2.2.2]oct-3-yl)-(5-tert-butyl-2-methoxybenzyl)amine, an NK1 receptor antagonist, was studied in human liver microsomes and recombinant human CYP isoforms. Liquid chromatography/mass spectrometry (LC/MS) and tandem mass spectrometry (LC/MS/MS) coupled to radioactive detection were used to detect and identify the metabolites. CJ-11,972 was extensively metabolized in human liver microsomes and recombinant human CYP 3A4/3A5 isoforms. A total of fourteen metabolites were identified by a combination of various MS techniques. The major metabolic pathways were due to oxidation of the tert-butyl moiety to form an alcohol (M6) and/or O-demethylation of the anisole moiety. The alcohol metabolite M6 was further oxidized to the corresponding aldehyde (M7) and carboxylic acid (M4). Two unusual metabolites (M13, M17), formed by C-demethylation of the tert-butyl group, were identified as 2-{3-[(2-benzhydryl-1-aza-bicyclo[2.2.2]oct-3-ylamino)methyl]-4-methoxyphenyl}propan-2-ol and (2-benzhydryl-1-aza-bicyclo[2.2.2]oct-3-yl)-(5-isopropenyl-2-methoxybenzyl)amine. A plausible mechanism for C-demethylation may involve oxidation of M6 to form an aldehyde metabolite (M7), followed by cytochrome P450-mediated deformylation leaving an unstable carbon-centered radical, which would quickly form either the alcohol metabolite M13 and the olefin metabolite M17.
Department of Pharmacokinetics, Dynamics and Metabolism, Pfizer Global Research and Development, Groton, CT 06340, USA. Chandra.prakash@pfizer.com
Chandra
C
Prakash
Jinyan
J
Lin
Kevin
K
Colizza
Zhuang
Z
Miao
D001559:Benzhydryl Compounds / Q000008:administration & dosage / Q000493:pharmacokinetics*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000008:administration & dosage / Q000493:pharmacokinetics*; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism*; D022781:Hepatocytes / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D008657:Metabolic Clearance Rate; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism*; D064729:Neurokinin-1 Receptor Antagonists; D011994:Recombinant Proteins / Q000378:metabolism*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
C523736:(2-benzhydryl-1-aza-bicyclo(2.2.2)oct-3-yl)-(5-tert-butyl-2-methoxybenzyl)amine; D001559:Benzhydryl Compounds; D019086:Bridged Bicyclo Compounds, Heterocyclic; D064729:Neurokinin-1 Receptor Antagonists; D011994:Recombinant Proteins; C510164:CYP3A5 protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human