title: A novel class of succinimide-derived negative allosteric modulators of metabotropic glutamate receptor subtype 1 provides insight into a disconnect in activity between the rat and human receptors.
abstract: Recent progress in the discovery of mGlu₁ allosteric modulators has suggested the modulation of mGlu₁ could offer possible treatment for a number of central nervous system disorders; however, the available chemotypes are inadequate to fully investigate the therapeutic potential of mGlu₁ modulation. To address this issue, we used a fluorescence-based high-throughput screening assay to screen an allosteric modulator-biased library of compounds to generate structurally diverse mGlu₁ negative allosteric modulator hits for chemical optimization. Herein, we describe the discovery and characterization of a novel mGlu₁ chemotype. This series of succinimide negative allosteric modulators, exemplified by VU0410425, exhibited potent inhibitory activity at rat mGlu₁ but was, surprisingly, inactive at human mGlu₁. VU0410425 and a set of chemically diverse mGlu₁ negative allosteric modulators previously reported in the literature were utilized to examine this species disconnect between rat and human mGlu₁ activity. Mutation of the key transmembrane domain residue 757 and functional screening of VU0410425 and the literature compounds suggests that amino acid 757 plays a role in the activity of these compounds, but the contribution of the residue is scaffold specific, ranging from critical to minor. The operational model of allosterism was used to estimate the binding affinities of each compound to compare to functional data. This novel series of mGlu₁ negative allosteric modulators provides valuable insight into the pharmacology underlying the disconnect between rat and human mGlu₁ activity, an issue that must be understood to progress the therapeutic potential of allosteric modulators of mGlu₁.
authors.affiliation: Vanderbilt Center for Neuroscience Drug Discovery and ‡Department of Pharmacology, Vanderbilt University Medical Center , Nashville, Tennessee 37232, United States.
authors.forename: Hyekyung P
authors.initials: HP
authors.lastname: Cho
authors.forename: Darren W
authors.initials: DW
authors.lastname: Engers
authors.forename: Daryl F
authors.initials: DF
authors.lastname: Venable
authors.forename: Colleen M
authors.initials: CM
authors.lastname: Niswender
authors.forename: Craig W
authors.initials: CW
authors.lastname: Lindsley
authors.forename: P Jeffrey
authors.initials: PJ
authors.lastname: Conn
authors.forename: Kyle A
authors.initials: KA
authors.lastname: Emmitte
authors.forename: Alice L
authors.initials: AL
authors.lastname: Rodriguez
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D003412:Cricetulus; D004353:Drug Evaluation, Preclinical; D018683:Excitatory Amino Acid Agents / Q000737:chemistry / Q000494:pharmacology*; D005453:Fluorescence; D057809:HEK293 Cells; D057166:High-Throughput Screening Assays; D006801:Humans; D009154:Mutation; D051381:Rats; D018094:Receptors, Metabotropic Glutamate / Q000235:genetics / Q000378:metabolism*; D013045:Species Specificity; D013388:Succinimides / Q000737:chemistry / Q000494:pharmacology*; D014162:Transfection
chemical_list: D018683:Excitatory Amino Acid Agents; D018094:Receptors, Metabotropic Glutamate; D013388:Succinimides; C104077:metabotropic glutamate receptor type 1; D002118:Calcium