(3-Cyano-5-fluorophenyl)biaryl negative allosteric modulators of mGlu(5): Discovery of a new tool compound with activity in the OSS mouse model of addiction.

Glutamate is the major excitatory transmitter in the mammalian CNS, exerting its effects through both ionotropic and metabotropic glutamate receptors. The metabotropic glutamate receptors (mGlus) belong to family C of the G-protein-coupled receptors (GPCRs). The eight mGlus identified to date are classified into three groups based on their structure, preferred signal transduction mechanisms, and pharmacology (Group I: mGlu(1) and mGlu(5); Group II: mGlu(2) and mGlu(3); Group III: mGlu(4), mGlu(6), mGlu(7), and mGlu(8)). Non-competitive antagonists, also known as negative allosteric modulators (NAMs), of mGlu(5) offer potential therapeutic applications in diseases such as pain, anxiety, gastroesophageal reflux disease (GERD), Parkinson's disease (PD), fragile X syndrome, and addiction. The development of SAR in a (3-cyano-5-fluorophenyl)biaryl series using our functional cell-based assay is described in this communication. Further characterization of a selected compound, 3-fluoro-5-(2-methylbenzo[d]thiazol-5-yl)benzonitrile, in additional cell based assays as well as in vitro assays designed to measure its metabolic stability and protein binding indicated its potential utility as an in vivo tool. Subsequent evaluation of the same compound in a pharmacokinetic study using intraperitoneal dosing in mice showed good exposure in both plasma and brain samples. The compound was efficacious in a mouse marble burying model of anxiety, an assay known to be sensitive to mGlu(5) antagonists. A new operant model of addiction termed operant sensation seeking (OSS) was chosen as a second behavioral assay. The compound also proved efficacious in the OSS model and constitutes the first reported example of efficacy with a small molecule mGlu(5) NAM in this novel assay.

Discovery of novel allosteric modulators of metabotropic glutamate receptor subtype 5 reveals chemical and functional diversity and in vivo activity in rat behavioral models of anxiolytic and antipsychotic activity.

Modulators of metabotropic glutamate receptor subtype 5 (mGluR5) may provide novel treatments for multiple central nervous system (CNS) disorders, including anxiety and schizophrenia. Although compounds have been developed to better understand the physiological roles of mGluR5 and potential usefulness for the treatment of these disorders, there are limitations in the tools available, including poor selectivity, low potency, and limited solubility. To address these issues, we developed an innovative assay that allows simultaneous screening for mGluR5 agonists, antagonists, and potentiators. We identified multiple scaffolds that possess diverse modes of activity at mGluR5, including both positive and negative allosteric modulators (PAMs and NAMs, respectively). 3-Fluoro-5-(3-(pyridine-2-yl)-1,2,4-oxadiazol-5-yl)benzonitrile (VU0285683) was developed as a novel selective mGluR5 NAM with high affinity for the 2-methyl-6-(phenylethynyl)-pyridine (MPEP) binding site. VU0285683 had anxiolytic-like activity in two rodent models for anxiety but did not potentiate phencyclidine-induced hyperlocomotor activity. (4-Hydroxypiperidin-1-yl)(4-phenylethynyl)phenyl)methanone (VU0092273) was identified as a novel mGluR5 PAM that also binds to the MPEP site. VU0092273 was chemically optimized to an orally active analog, N-cyclobutyl-6-((3-fluorophenyl)ethynyl)nicotinamide hydrochloride (VU0360172), which is selective for mGluR5. This novel mGluR5 PAM produced a dose-dependent reversal of amphetamine-induced hyperlocomotion, a rodent model predictive of antipsychotic activity. Discovery of structurally and functionally diverse allosteric modulators of mGluR5 that demonstrate in vivo efficacy in rodent models of anxiety and antipsychotic activity provide further support for the tremendous diversity of chemical scaffolds and modes of efficacy of mGluR5 ligands. In addition, these studies provide strong support for the hypothesis that multiple structurally distinct mGluR5 modulators have robust activity in animal models that predict efficacy in the treatment of CNS disorders.

Synthesis and SAR of novel, 4-(phenylsulfamoyl)phenylacetamide mGlu4 positive allosteric modulators (PAMs) identified by functional high-throughput screening (HTS).

Herein we disclose the synthesis and SAR of a series of 4-(phenylsulfamoyl)phenylacetamide compounds as mGlu(4) positive allosteric modulators (PAMs) that were identified via a functional HTS. An iterative parallel approach to these compounds culminated in the discovery of VU0364439 (11) which represents the most potent (19.8 nM) mGlu(4) PAM reported to date.

3-Cyano-5-fluoro-N-arylbenzamides as negative allosteric modulators of mGlu(5): Identification of easily prepared tool compounds with CNS exposure in rats.

Development of SAR in a 3-cyano-5-fluoro-N-arylbenzamide series of non-competitive antagonists of mGlu(5) using a functional cell-based assay is described in this Letter. Further characterization of selected potent compounds in in vitro assays designed to measure their metabolic stability and protein binding is also presented. Subsequent evaluation of two new compounds in pharmacokinetic studies using intraperitoneal dosing in rats demonstrated good exposure in both plasma and brain samples.

A selective allosteric potentiator of the M1 muscarinic acetylcholine receptor increases activity of medial prefrontal cortical neurons and restores impairments in reversal learning.

M(1) muscarinic acetylcholine receptors (mAChRs) may represent a viable target for treatment of disorders involving impaired cognitive function. However, a major limitation to testing this hypothesis has been a lack of highly selective ligands for individual mAChR subtypes. We now report the rigorous molecular characterization of a novel compound, benzylquinolone carboxylic acid (BQCA), which acts as a potent, highly selective positive allosteric modulator (PAM) of the rat M(1) receptor. This compound does not directly activate the receptor, but acts at an allosteric site to increase functional responses to orthosteric agonists. Radioligand binding studies revealed that BQCA increases M(1) receptor affinity for acetylcholine. We found that activation of the M(1) receptor by BQCA induces a robust inward current and increases spontaneous EPSCs in medial prefrontal cortex (mPFC) pyramidal cells, effects which are absent in acute slices from M(1) receptor knock-out mice. Furthermore, to determine the effect of BQCA on intact and functioning brain circuits, multiple single-unit recordings were obtained from the mPFC of rats that showed BQCA increases firing of mPFC pyramidal cells in vivo. BQCA also restored discrimination reversal learning in a transgenic mouse model of Alzheimer's disease and was found to regulate non-amyloidogenic APP processing in vitro, suggesting that M(1) receptor PAMs have the potential to provide both symptomatic and disease modifying effects in Alzheimer's disease patients. Together, these studies provide compelling evidence that M(1) receptor activation induces a dramatic excitation of PFC neurons and suggest that selectively activating the M(1) mAChR subtype may ameliorate impairments in cognitive function.

Synthesis and evaluation of a series of heterobiarylamides that are centrally penetrant metabotropic glutamate receptor 4 (mGluR4) positive allosteric modulators (PAMs).

We report the synthesis and evaluation of a series of heterobiaryl amides as positive allosteric modulators of mGluR4. Compounds 9b and 9c showed submicromolar potency at both human and rat mGluR4. In addition, both 9b and 9c were shown to be centrally penetrant in rats using nontoxic vehicles, a major advance for the mGluR4 field.

Associations between CYP2B6 polymorphisms and pharmacokinetics after a single dose of nevirapine or efavirenz in African americans.

BACKGROUND: Polymorphisms in CYP2B6 affect the steady-state plasma concentrations of nevirapine and efavirenz. In many resource-limited countries, a single dose of nevirapine has been widely prescribed to pregnant women at delivery, to reduce mother-to-child transmission of human immunodeficiency virus type 1 (HIV-1). We characterized associations between genetic polymorphisms and the pharmacokinetics of single doses of nevirapine and efavirenz. METHODS: Plasma drug concentrations were determined over the 13-day period after administration of a 200-mg oral dose of nevirapine to nonpregnant, HIV-negative African Americans. A 600-mg oral dose of efavirenz was subsequently administered, and pharmacokinetic sampling was repeated. Pharmacokinetic parameters were estimated using a noncompartmental approach. Primary analyses involved 2 CYP2B6 polymorphisms (516G --> T and 983T --> C) known to predict increased steady-state plasma nevirapine and efavirenz exposure. Exploratory analyses involved another 51 polymorphisms in CYP2B6, ABCB1, CYP3A4, and CYP3A5. RESULTS: On the basis of the composite CYP2B6 516/983 genotype, the 34 participants comprised 10 extensive, 17 intermediate, and 7 slow metabolizer genotypes. The composite CYP2B6 516/983 genotype was significantly associated with plasma drug exposure and clearance for efavirenz but not nevirapine. Exploratory analyses suggested possible associations between additional CYP2B6 polymorphisms and the pharmacokinetics of nevirapine and efavirenz. CONCLUSIONS: Selective pressure for drug-resistant HIV-1 after administration of single-dose nevirapine may not differ substantially according to CYP2B6 516/983 genotype. Additional polymorphisms, genes, and populations warrant further study.