title: Identification of glutathione conjugates of acetylene-containing positive allosteric modulators of metabotropic glutamate receptor subtype 5.
abstract: A recent medicinal chemistry campaign to identify positive allosteric modulators (PAMs) of metabotropic glutamate receptor subtype 5 (mGluR5) led to the discovery of potent compounds featuring an oxazolidinone structural core flanked by biaryl acetylene and haloaryl moieties. However, biotransformation studies of some of these mGluR5 PAMs demonstrated the formation of glutathione (GSH) conjugates. The conjugates in question were formed independently of NADPH as the main products in liver microsomes and liver cytosol (rat and human) and exhibited masses that were 307 u greater than their respective substrates, indicating the involvement of a reductive step in the formation of these metabolites. To further characterize the relevant metabolic sequences, GSH conjugates of (4R,5R)-5-(3-fluorophenyl)-4-(5-(pyrazin-2-ylethynyl)pyridin-3-yl)oxazolidin-2-one and (4R,5R)-5-(4-fluorophenyl)-4-(6-((3-fluoropyridin-2-yl)ethynyl)pyridin-2-yl)oxazolidin-2-one were biosynthesized and isolated. Subsequent analysis by NMR showed that GSH had reacted with the acetylene carbon atoms of these mGluR5 PAMs, suggesting a conjugate addition mechanism and implicating cytosolic and microsomal GSH S-transferases (GSTs) in catalysis. Interestingly, five closely related mGluR5 PAMs were not similarly prone to the formation of GSH conjugates in vitro. These compounds also featured acetylenes, but were flanked by either phenyl or cyclohexyl rings, which indicated that the formation of GSH conjugates was influenced by proximal functional groups that modulated the electron density of the triple bond and/or differences in enzyme-substrate specificity. These results informed an ongoing drug-discovery effort to identify mGluR5 PAMs with drug-like properties and a low risk of reactivity with endogenous thiols.
authors: Department of Biotransformation (X.Z., B.M.J.), Discovery Analytical Sciences (X.S.H.), Neuroscience Chemistry (A.P.D., L.B.S., F.Y., H.H.), Bristol-Myers Squibb Company, Wallingford, Connecticut; and Department of Biotransformation, Bristol-Myers Squibb Company, Princeton, New Jersey (Y.-Z.S.) xiaoliang.zhuo@bms.com.
authors: Xiaoliang
authors: X
authors: Zhuo
authors: Department of Biotransformation (X.Z., B.M.J.), Discovery Analytical Sciences (X.S.H.), Neuroscience Chemistry (A.P.D., L.B.S., F.Y., H.H.), Bristol-Myers Squibb Company, Wallingford, Connecticut; and Department of Biotransformation, Bristol-Myers Squibb Company, Princeton, New Jersey (Y.-Z.S.).
authors: Xiaohua Stella
authors: XS
authors: Huang
authors: Department of Biotransformation (X.Z., B.M.J.), Discovery Analytical Sciences (X.S.H.), Neuroscience Chemistry (A.P.D., L.B.S., F.Y., H.H.), Bristol-Myers Squibb Company, Wallingford, Connecticut; and Department of Biotransformation, Bristol-Myers Squibb Company, Princeton, New Jersey (Y.-Z.S.).
authors: Andrew P
authors: AP
authors: Degnan
authors: Department of Biotransformation (X.Z., B.M.J.), Discovery Analytical Sciences (X.S.H.), Neuroscience Chemistry (A.P.D., L.B.S., F.Y., H.H.), Bristol-Myers Squibb Company, Wallingford, Connecticut; and Department of Biotransformation, Bristol-Myers Squibb Company, Princeton, New Jersey (Y.-Z.S.).
authors: Lawrence B
authors: LB
authors: Snyder
authors: Department of Biotransformation (X.Z., B.M.J.), Discovery Analytical Sciences (X.S.H.), Neuroscience Chemistry (A.P.D., L.B.S., F.Y., H.H.), Bristol-Myers Squibb Company, Wallingford, Connecticut; and Department of Biotransformation, Bristol-Myers Squibb Company, Princeton, New Jersey (Y.-Z.S.).
authors: Fukang
authors: F
authors: Yang
authors: Department of Biotransformation (X.Z., B.M.J.), Discovery Analytical Sciences (X.S.H.), Neuroscience Chemistry (A.P.D., L.B.S., F.Y., H.H.), Bristol-Myers Squibb Company, Wallingford, Connecticut; and Department of Biotransformation, Bristol-Myers Squibb Company, Princeton, New Jersey (Y.-Z.S.).
authors: Hong
authors: H
authors: Huang
authors: Department of Biotransformation (X.Z., B.M.J.), Discovery Analytical Sciences (X.S.H.), Neuroscience Chemistry (A.P.D., L.B.S., F.Y., H.H.), Bristol-Myers Squibb Company, Wallingford, Connecticut; and Department of Biotransformation, Bristol-Myers Squibb Company, Princeton, New Jersey (Y.-Z.S.).
authors: Yue-Zhong
authors: YZ
authors: Shu
authors: Department of Biotransformation (X.Z., B.M.J.), Discovery Analytical Sciences (X.S.H.), Neuroscience Chemistry (A.P.D., L.B.S., F.Y., H.H.), Bristol-Myers Squibb Company, Wallingford, Connecticut; and Department of Biotransformation, Bristol-Myers Squibb Company, Princeton, New Jersey (Y.-Z.S.).
authors: Benjamin M
authors: BM
authors: Johnson
mesh_terms: D000480:Alkynes / Q000737:chemistry / Q000493:pharmacokinetics* / Q000494:pharmacology; D000494:Allosteric Regulation / Q000187:drug effects*; D000818:Animals; D003600:Cytosol / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D050217:Metabolic Detoxication, Phase II; D008862:Microsomes, Liver / Q000378:metabolism; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D051381:Rats; D064529:Receptor, Metabotropic Glutamate 5 / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D000480:Alkynes; C578935:GRM5 protein, human; C578937:Grm5 protein, rat; D064529:Receptor, Metabotropic Glutamate 5; D005978:Glutathione