title: Elucidating the mechanism of cytochrome P450-mediated pyrimidine ring conversion to pyrazole metabolites with the BACE1 inhibitor GNE-892 in rats.
abstract: We investigated an uncommon biotransformation of pyrimidine during the metabolism of GNE-892 ((R)-2-amino-1,3',3'-trimethyl-7'-(pyrimidin-5-yl)-3',4'-dihydro-2'H-spiro[imidazole-4,1'-naphthalen]-5(1H)-one), a β-secretase 1 inhibitor. Three novel metabolites, formed by conversion of pyrimidine to pyrazole, were observed in the (14)C-radiolabeled mass balance study in rats. Their structures were characterized by high-resolution mass spectrometry and nuclear magnetic resonance. Although these metabolites accounted for <5% of the administered dose, their unique nature prompted us to conduct further investigations. The pyrazole-containing metabolites were formed in vitro with rat hepatocytes and liver microsomes, which supported that they were formed during hepatic metabolism. Further, their generation was inhibited by 1-aminobenzotriazole, indicating involvement of cytochrome P450s. Studies with rat recombinant enzymes identified that CYP2D2 generated the N-hydroxypyrazole metabolite from GNE-892. This biotransformation proceeded through multiple steps from the likely precursor, pyrimidine N-oxide. On the basis of these data, we propose a mechanism in which the pyrimidine is activated via N-oxidation, followed by a second oxidative process that opens the pyrimidine ring to form a formamide intermediate. After hydrolysis of the formamide, a carbon is lost as formic acid, together with ring closure to form the pyrazole ring. This article highlights a mechanistic approach for determining the biotransformation of the pyrimidine to a pyrazole for GNE-892.
authors.affiliation: Departments of Drug Metabolism and Pharmacokinetics (R.T., S.M., Q.Y., C.E.H., X.L., S.C.K), Small Molecule Pharmaceutical Sciences (A.D.), and Discovery Chemistry (M.S.), Genentech, Inc., South San Francisco, California; XenoBiotic Laboratories, Inc., Plainsboro, New Jersey (H.K., Y.Y.); and Array BioPharma, Boulder, Colorado (K.W.H., N.C.K.).
authors.forename: Ryan
authors.initials: R
authors.lastname: Takahashi
authors.forename: Shuguang
authors.initials: S
authors.lastname: Ma
authors.forename: Alan
authors.initials: A
authors.lastname: Deese
authors.forename: Qin
authors.initials: Q
authors.lastname: Yue
authors.forename: Heasook
authors.initials: H
authors.lastname: Kim-Kang
authors.forename: Yijun
authors.initials: Y
authors.lastname: Yi
authors.forename: Michael
authors.initials: M
authors.lastname: Siu
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Hunt
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Kallan
authors.forename: Cornelis E C A
authors.initials: CE
authors.lastname: Hop
authors.forename: Xingrong
authors.initials: X
authors.lastname: Liu
authors.forename: S Cyrus
authors.initials: SC
authors.lastname: Khojasteh
mesh_terms: D053829:Amyloid Precursor Protein Secretases / Q000037:antagonists & inhibitors*; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism*; D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors*; D001646:Bile / Q000378:metabolism; D001711:Biotransformation; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D004791:Enzyme Inhibitors / Q000378:metabolism* / Q000493:pharmacokinetics / Q000652:urine; D005243:Feces / Q000737:chemistry; D022781:Hepatocytes / Q000187:drug effects / Q000201:enzymology; D007093:Imidazoles / Q000378:metabolism* / Q000493:pharmacokinetics / Q000652:urine; D008297:Male; D011720:Pyrazoles / Q000378:metabolism*; D011743:Pyrimidines / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013141:Spiro Compounds / Q000378:metabolism* / Q000493:pharmacokinetics / Q000652:urine; D053719:Tandem Mass Spectrometry
chemical_list: C584427:2-amino-1,3',3'-trimethyl-7'-(pyrimidin-5-yl)-3',4'-dihydro-2'H-spiro(imidazole-4,1'-naphthalen)-5(1H)-one; D004791:Enzyme Inhibitors; D007093:Imidazoles; D011720:Pyrazoles; D011743:Pyrimidines; D013141:Spiro Compounds; C031280:pyrazole; D001189:Aryl Hydrocarbon Hydroxylases; C119985:Cyp2d2 protein, rat; D053829:Amyloid Precursor Protein Secretases; D016282:Aspartic Acid Endopeptidases; C509281:Bace1 protein, rat; C030986:pyrimidine