The metabotropic glutamate receptor 7 allosteric modulator AMN082: a monoaminergic agent in disguise?

Metabotropic glutamate receptor 7 (mGluR7) remains the most elusive of the eight known mGluRs primarily because of the limited availability of tool compounds to interrogate its potential therapeutic utility. The discovery of N,N'-dibenzhydrylethane-1,2-diamine dihydrochloride (AMN082) as the first orally active, brain-penetrable, mGluR7-selective allosteric agonist by Mitsukawa and colleagues (Proc Natl Acad Sci USA 102:18712-18717, 2005) provides a means to investigate this receptor system directly. AMN082 demonstrates mGluR7 agonist activity in vitro and interestingly has a behavioral profile that supports utility across a broad spectrum of psychiatric disorders including anxiety and depression.

Identification of 3-sulfonylindazole derivatives as potent and selective 5-HT(6) antagonists.

As part of our efforts to develop agents for cognitive enhancement, we have been focused on the 5-HT(6) receptor in order to identify potent and selective ligands for this purpose. Herein we report the identification of a novel series of 3-sulfonylindazole derivatives with acyclic amino side chains as potent and selective 5-HT(6) antagonists. The synthesis and detailed SAR of this class of compounds are reported.

Monoacylglycerol lipase activity is a critical modulator of the tone and integrity of the endocannabinoid system.

Endocannabinoids are lipid molecules that serve as natural ligands for the cannabinoid receptors CB1 and CB2. They modulate a diverse set of physiological processes such as pain, cognition, appetite, and emotional states, and their levels and functions are tightly regulated by enzymatic biosynthesis and degradation. 2-Arachidonoylglycerol (2-AG) is the most abundant endocannabinoid in the brain and is believed to be hydrolyzed primarily by the serine hydrolase monoacylglycerol lipase (MAGL).

Novel alpha-7 nicotinic acetylcholine receptor agonists containing a urea moiety: identification and characterization of the potent, selective, and orally efficacious agonist 1-[6-(4-fluorophenyl)pyridin-3-yl]-3-(4-piperidin-1-ylbutyl) urea (SEN34625/WYE-103914).

Alpha-7 nicotinic acetylcholine receptor (alpha7 nAChR) agonists are promising therapeutic candidates for the treatment of cognitive impairment. We report a series of novel, potent small molecule agonists (4-18) of the alpha7 nAChR deriving from our continuing efforts in the areas of Alzheimer's disease and schizophrenia. One of the compounds of the series containing a urea moiety (16) was further shown to be a selective agonist of the alpha7 nAChR with excellent in vitro and in vivo profiles, brain penetration, and oral bioavailability and demonstrated in vivo efficacy in multiple behavioral cognition models.

Potent dihydroquinolinone dopamine D2 partial agonist/serotonin reuptake inhibitors for the treatment of schizophrenia.

A dihydroquinolinone moiety was found to be a potent serotonin reuptake inhibitor pharmacophore when combined with certain amines. This fragment was coupled with selected D(2) ligands to prepare a series of dual acting compounds with attractive in vitro profiles as dopamine D(2) partial agonists and serotonin reuptake inhibitors. Structure-activity studies revealed that the linker plays a key role in contributing to D(2) affinity, function, and SRI activity.

Preclinical characterization of BRL 44408: antidepressant- and analgesic-like activity through selective alpha2A-adrenoceptor antagonism.

Biogenic amines such as norepinephrine, dopamine, and serotonin play a well-described role in the treatment of mood disorders and some types of pain. As alpha2A-adrenoceptors regulate the release of these neurotransmitters, we examined the therapeutic potential of BRL 44408, a potent (Ki=8.5 nM) and selective (>50-fold) alpha2A-adrenoceptor antagonist (K(B)=7.

Development of an improved IP(1) assay for the characterization of 5-HT(2C) receptor ligands.

The 5-hydroxytryptamine 2C (5-HT(2C)) receptor is a member of the serotonin 5-HT(2) subfamily of G-protein-coupled receptors signaling predominantly via the phospholipase C (PLC) pathway. Stimulation of phosphoinositide (PI) hydrolysis upon 5-HT(2C) receptor activation is traditionally assessed by measuring inositol monophosphate (IP(1)) using time-consuming and labor-intensive anion exchange radioactive assays. In this study, we have developed and optimized a cellular IP(1) assay using homogeneous time-resolved fluorescence (HTRF), a fluorescence resonance energy transfer (FRET)-based technology (Cisbio; Gif sur Yvette, France).

Tetrahydrocarbazole-based serotonin reuptake inhibitor/dopamine D2 partial agonists for the potential treatment of schizophrenia.

A 5-fluoro-tetrahydrocarbazole serotonin reuptake inhibitor (SRI) building block was combined with a variety of linkers and dopamine D2 receptor ligands in an attempt to identify potent D2 partial agonist/SRI molecules for treatment of schizophrenia. This approach has the potential to treat a broader range of symptoms compared to existing therapies. Selected compounds in this series demonstrate high affinity for both targets and D2 partial agonism in cell-based and in vivo assays.

Identification of a novel series of 3-piperidinyl-5-sulfonylindazoles as potent 5-HT6 ligands.

Cognitive dysfunction is a characteristic of various forms of dementia such as Alzheimer's disease (AD) and a core feature of schizophrenia. As part of our continuing efforts to develop agents for cognitive enhancement, we have been focused on the 5-HT(6) receptor-one of the emerging therapeutic targets in this area. Herein, we report the identification of a novel series of 3-piperidinyl-5-sulfonylindazole derivatives as potent 5-HT(6) antagonists.

1-Sulfonylindazoles as potent and selective 5-HT6 ligands.

As part of our continuing efforts to identify therapeutics for CNS diseases, such as schizophrenia and Alzheimer's disease (AD), we have been focused on the 5-HT(6) receptor in an attempt to identify ligands as a potential treatment for cognitive dysfunction. Herein we report the identification of a novel series of 1-sulfonylindazole derivatives as potent and selective 5-HT(6) antagonists. The synthesis and SAR of this class of compounds are reported.

Procognitive and neuroprotective activity of a novel alpha7 nicotinic acetylcholine receptor agonist for treatment of neurodegenerative and cognitive disorders.

The alpha7 nicotinic acetylcholine receptor (nAChR) is a promising target for treatment of cognitive dysfunction associated with Alzheimer's disease and schizophrenia. Here, we report the pharmacological properties of 5-morpholin-4-yl-pentanoic acid (4-pyridin-3-yl-phenyl)-amide [SEN12333 (WAY-317538)], a novel selective agonist of alpha7 nAChR. SEN12333 shows high affinity for the rat alpha7 receptor expressed in GH4C1 cells (K(i) = 260 nM) and acts as full agonist in functional Ca(2+) flux studies (EC(50) = 1.

Old and new pharmacology: positive allosteric modulation of the alpha7 nicotinic acetylcholine receptor by the 5-hydroxytryptamine(2B/C) receptor antagonist SB-206553 (3,5-dihydro-5-methyl-N-3-pyridinylbenzo[1,2-b:4,5-b']di pyrrole-1(2H)-carboxamide).

The alpha7 nicotinic acetylcholine receptor (nAChR) has been implicated in Alzheimer's disease and schizophrenia, leading to efforts targeted toward discovering agonists and positive allosteric modulators (PAMs) of this receptor. In a Ca2+ flux fluorometric imaging plate reader assay, SB-206553 (3,5-dihydro-5-methyl -N-3-pyridinylbenzo [1, 2-b:4,5 -b']-di pyrrole-1(2H)-carboxamide), a compound known as a 5-hydroxytryptamine(2B/2C) receptor antagonist, produced an 8-fold potentiation of the evoked calcium signal in the presence of an EC(20) concentration of nicotine and a corresponding EC(50) of 1.5 muM for potentiation of EC(20) nicotine responses in GH4C1 cells expressing the alpha7 receptor.

Scintillation proximity assay in lead discovery.

Background: Scintillation proximity assay (SPA) is a homogeneous scintillant bead-based platform for the measurement of biological processes and plays an important role in the identification of active chemical entities in drug discovery.

Objective: The design and development of solid-phase SPA approaches are examined and compared with alternative non-radiometric fluorescence-based technologies.

Methods: This review provides background on the principle of SPA and its application to biomolecular interactions from a variety of biological sources.

Development of a scintillation proximity assay binding method for the human 5-hydroxytryptamine 6 receptor using intact cells.

We describe the first validated scintillation proximity assay (SPA) binding method for quantitation of (3)H-labeled d-lysergic acid diethylamide (LSD) binding to recombinant human 5-hydroxytryptamine 6 (5-HT(6)) receptors expressed in Chinese hamster ovary (CHO)-Dukx and HeLa cells. The assay was developed using intact cells as a receptor source because membrane fractions derived from these cells failed to discern specific binding from a high level of nonspecific binding. The pharmacological binding profile of seven 5-HT(6) agonists and antagonists using intact CHO-Dukx/5-HT(6) cells in the SPA format was similar to data obtained from a filtration binding assay using HeLa/5-HT(6) membranes.

A regiospecific synthesis of a series of 1-sulfonyl azepinoindoles as potent 5-HT6 ligands.

A regiospecific synthesis of a series of 1-sulfonyl azepinoindoles as potent 5-HT6 ligands is reported.

In vitro screening strategies for nicotinic receptor ligands.

A common historical strategy to the discovery of nicotinic receptor ligands has involved the use of radioligand-binding assays for ligand identification in combination with two-electrode voltage clamp in Xenopus oocytes for electrophysiological characterization. More recently, higher-throughput methodologies have replaced these approaches to accommodate screening of large compound libraries and to provide increased capacity for electrophysiological profiling in mammalian cell lines. We, and others, have implemented cell-based screening assays using the fluorometric imaging plate reader (FLIPR) for primary and lead optimization screening of nicotinic receptor agonists and positive allosteric modulators (PAMs).

Rb+ efflux through functional activation of cardiac KCNQ1/minK channels by the benzodiazepine R-L3 (L-364,373).

The slow delayed rectifier K+ current, Iks, encoded by KCNQ1 (KvLQT1)/KCNE1 (mink) genes, contributes to cardiac action potential repolarization and determines the heartbeat rate. Mutations in either KCNQ1 or KCNE1 that reduce Iks cause long-QT syndrome (LQTS), a disorder of ventricular repolarization that results in cardiac arrhythmia and sudden death. A well-recognized potential treatment for LQTS caused by reduction of Iks is to enhance functional activation of cardiac KCNQ1/KCNE1 channels.

Distinct functional profiles of aripiprazole and olanzapine at RNA edited human 5-HT2C receptor isoforms.

In this study we have functionally characterized aripiprazole (OPC-14597; 7-(4-[4-(2,3-dichlorophenyl)-1-piperazinyl]butyloxy-3,4-dihydro-2-(1H)-quinolinone), the prototype of a new generation antipsychotic drug termed dopamine-serotonin-system stabilizer, in cells expressing 5-hydroxytryptamine2 (5-HT2) receptor subtypes in comparison with olanzapine. In Chinese hamster ovary (CHO) cells stably expressing 5-HT2 receptors, aripiprazole displayed a dual agonist/antagonist profile for 5-HT2C receptor (VNI isoform) mediated calcium signaling (EC50 1070 nM, IC50 281 nM). It exhibited no appreciable 5-HT2A or 5-HT2B agonism, whereas it antagonized 5-HT-stimulated calcium increase at either 5-HT2A or 5-HT2B receptor expressed in CHO cells (IC50s of 369 and 0.

Synthesis and biological activities of aryl-ether-, biaryl-, and fluorene-aspartic acid and diaminopropionic acid analogs as potent inhibitors of the high-affinity glutamate transporter EAAT-2.

Excitatory amino acid transporters (EAATs) play a pivotal role in maintaining glutamate homeostasis in the mammalian central nervous system, with the EAAT-2 subtype thought to be responsible for the bulk of the glutamate uptake in forebrain regions. A complete elucidation of the functional role of EAAT-2 has been hampered by the lack of potent and selective pharmacological tools. In this study, we describe the synthesis and biological activities of novel aryl-ether, biaryl-, and fluorene-aspartic acid and diaminopropionic acid analogs as potent inhibitors of EAAT-2.

Characterization of novel aryl-ether, biaryl, and fluorene aspartic acid and diaminopropionic acid analogs as potent inhibitors of the high-affinity glutamate transporter EAAT2.

In this study, we describe the pharmacological characterization of novel aryl-ether, biaryl, and fluorene aspartic acid and diaminopropionic acid analogs as potent inhibitors of EAAT2, the predominant glutamate transporter in forebrain regions. The rank order of potency determined for the inhibition of human EAAT2 was N(4)-[4-(2-bromo-4,5-difluorophenoxy)phenyl]-L-asparagine (WAY-213613) (IC(50) = 85 +/- 5 nM) > N(4)-(2'-methyl-1,1'-biphenyl-4-yl)-L-asparagine (WAY-213394) (IC(50) = 145 +/- 22 nM) = N(4)-[7-(trifluoromethyl)-9H-fluoren-2-yl]-L-asparagine (WAY-212922) (IC(50) = 157 +/- 11 nM) = 3-{[(4'-chloro-2-methyl-1,1'-biphenyl-4-yl)carbonyl]amino}-L-alanine (WAY-211686) (IC(50) = 190 +/- 10 nM). WAY-213613 was the most selective of the compounds examined, with IC(50) values for inhibition of EAAT1 and EAAT3 of 5 and 3.

Validation of an atomic absorption rubidium ion efflux assay for KCNQ/M-channels using the ion Channel Reader 8000.

M-channels (M-current), encoded by KCNQ2/3 K(+) channel genes, have emerged as novel drug targets for a number of neurological disorders. The lack of direct high throughput assays combined with the low throughput of conventional electrophysiology (EP) has impeded rapid screening and evaluation of K(+)-channel modulators. Development of a sensitive and efficient assay for the direct measurement of M-current activity is critical for identifying novel M-channel modulators and subsequent investigation of their therapeutic potential.

Characterization of two novel N-methyl-D-aspartate antagonists: EAA-090 (2-[8,9-dioxo-2,6-diazabicyclo [5.2.0]non-1(7)-en2-yl]ethylphosphonic acid) and EAB-318 (R-alpha-amino-5-chloro-1-(phosphonomethyl)-1H-benzimidazole-2-propanoic acid hydrochloride).

Two novel N-methyl-d-aspartate (NMDA) antagonists with unique chemical structures, EAA-090 (2-[8,9-dioxo-2, 6-diazabicyclo[5.2.0]non-1(7)-en2-yl]ethylphosphonic acid) and EAB-318 (R-alpha-amino-5-chloro-1-(phosphonomethyl)-1H-benzimidazole-2-propanoic acid hydrochloride), were compared with CGS-19755 (Selfotel) in ligand binding, electrophysiology, and neuroprotection assays.