Positive allosteric modulators (PAMs) of metabotropic glutamate receptor subtype 5 (mGlu5) enhance N-methyl-D-aspartate receptor function and may represent a novel approach for the treatment of schizophrenia. ADX47273 [S-(4-fluoro-phenyl)-{3-[3-(4-fluoro-phenyl)-[1,2,4]oxadiazol-5-yl]-piperidin-1-yl}-methanone], a recently identified potent and selective mGlu5 PAM, increased (9-fold) the response to threshold concentration of glutamate (50 nM) in fluorometric Ca 2ϩ assays (EC 50 ϭ 170 nM) in human embryonic kidney 293 cells expressing rat mGlu5. In the same system, ADX47273 dose-dependently shifted mGlu5 receptor glutamate response curve to the left (9-fold at 1 M) and competed for binding of3 H]quisqualate. In vivo, ADX47273 increased extracellular signal-regulated kinase and cAMP-responsive element-binding protein phosphorylation in hippocampus and prefrontal cortex, both of which are critical for glutamate-mediated signal transduction mechanisms. In models sensitive to antipsychotic drug treatment, ADX47273 reduced rat-conditioned avoidance responding [minimal effective dose (MED) ϭ 30 mg/kg i.p.] and decreased mouse apomorphine-induced climbing (MED ϭ 100 mg/kg i.p.), with little effect on stereotypy or catalepsy. Furthermore, ADX47273 blocked phencyclidine, apomorphine, and amphetamine-induced locomotor activities (MED ϭ 100 mg/kg i.p.) in mice and decreased extracellular levels of dopamine in the nucleus accumbens, but not in the striatum, in rats. In cognition models, ADX47273 increased novel object recognition (MED ϭ 1 mg/kg i.p.) and reduced impulsivity in the fivechoice serial reaction time test (MED ϭ 10 mg/kg i.p.) in rats. Taken together, these effects are consistent with the hypothesis that allosteric potentiation of mGlu5 may provide a novel approach for development of antipsychotic and procognitive agents.The metabotropic glutamate receptor (mGlu) receptor family includes eight G-protein-coupled receptor (GPCR) subtypes classified on the basis of structural homology, Article, publication date, and citation information can be found at http://jpet.aspetjournals.org. doi:10.1124/jpet.108.136580.ABBREVIATIONS: mGlu, metabotropic glutamate receptor; GPCR, G-protein-coupled receptor; PAM, positive allosteric modulator; CPPHA, 2, NMDA, MPEP,

Purpose:Fabry disease is an X-linked lysosomal storage disorder caused by mutations in the α-galactosidase A gene. Migalastat, a pharmacological chaperone, binds to specific mutant forms of α-galactosidase A to restore lysosomal activity.Methods:A pharmacogenetic assay was used to identify the α-galactosidase A mutant forms amenable to migalastat. Six hundred Fabry disease–causing mutations were expressed in HEK-293 (HEK) cells; increases in α-galactosidase A activity were measured by a good laboratory practice (GLP)-validated assay (GLP HEK/Migalastat Amenability Assay). The predictive value of the assay was assessed based on pharmacodynamic responses to migalastat in phase II and III clinical studies.Results:Comparison of the GLP HEK assay results in in vivo white blood cell α-galactosidase A responses to migalastat in male patients showed high sensitivity, specificity, and positive and negative predictive values (≥0.875). GLP HEK assay results were also predictive of decreases in kidney globotriaosylceramide in males and plasma globotriaosylsphingosine in males and females. The clinical study subset of amenable mutations (n = 51) was representative of all 268 amenable mutations identified by the GLP HEK assay.Conclusion:The GLP HEK assay is a clinically validated method of identifying male and female Fabry patients for treatment with migalastat.Genet Med 19 4, 430–438.

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A fluorescent imaging plate reader (FLIPR) membrane potential (V m ) assay was evaluated for pharmacological characterization and high-throughput screening (HTS) of rat glycine transporter type 2 (rGlyT 2 ) in a stable rGlyT 2 -HEK cell line. Data show that glycine activation of rGlyT 2 consistently results in a concentration-dependent V m response on the FLIPR that is blocked by the potent and selective GlyT 2 antagonist 4-benzyloxy-3,5-dimethoxy-N-[1-dimethylaminocyclopentyl)methyl]-benz-amide (Org-25543). Agonist and antagonist pharmacologies match those reported using conventional [ 3 H]glycine uptake assays and electrophysiology. The glycine response is dependent on buffer ionic composition consistent with GlyT 2 physiology. Assay signal-to-background and coefficient of variation meets sufficient statistical criteria to conduct HTS. The results of a screen of the chemical inventory demonstrate that the assay is able to successfully identify and confirm GlyT 2 inhibitors. The advantages of this assay are its homogeneity, compatibility with both 96-and 384-well formats, and lack of radioactivity usage. Thus, the authors conclude that a fluorescence-based V m assay on FLIPR is a viable approach for identification and pharmacological profiling of small molecule modulators of the electrogenic transporter rGlyT 2 . (Journal of Biomolecular Screening 2005:365-373)

Voltage-gated sodium channels (NaChs) are relevant targets for pain, epilepsy, and a variety of neurological and cardiac disorders. Traditionally, it has been difficult to develop structure-activity relationships for NaCh inhibitors due to rapid channel kinetics and state-dependent compound interactions. Membrane potential (V m ) dyes in conjunction with a high-throughput fluorescence imaging plate reader (FLIPR) offer a satisfactory 1st-tier solution. Thus, the authors have developed a FLIPR V m assay of rat Na v 1.2 NaCh. Channels were opened by addition of veratridine, and V m dye responses were measured. The IC 50 values from various structural classes of compounds were compared to the resting state binding constant (K r ) and inactivated state binding constant (K i ) obtained using patch-clamp electrophysiology (EP). The FLIPR values correlated with K i but not K r . FLIPR IC 50 values fell within 0.1-to 1.5-fold of EP K i values, indicating that the assay generally reports use-dependent inhibition rather than resting state block. The Library of Pharmacologically Active Compounds (LOPAC, Sigma) was screened. Confirmed hits arose from diverse classes such as dopamine receptor antagonists, serotonin transport inhibitors, and kinase inhibitors. These data suggest that NaCh inhibition is inherent in a diverse set of biologically active molecules and may warrant counterscreening NaChs to avoid unwanted secondary pharmacology. (Journal of Biomolecular Screening 2006: 29-39)