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.
Prakash
Chandra
C
Department of Pharmacokinetics, Dynamics and Metabolism, Pfizer Global Research and Development, Groton, CT 06340, USA. Chandra.prakash@pfizer.com
Lin
Jinyan
J
Colizza
Kevin
K
Miao
Zhuang
Z
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