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Find video protocols related to scientific articles indexed in Pubmed.
Discovery of Desketoraloxifene Analogues as Inhibitors of Mammalian, Pseudomonas aeruginosa, and NAPE Phospholipase D Enzymes.
ACS Chem. Biol.
PUBLISHED: 11-11-2014
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Phospholipase D (PLD) hydrolyses cellular lipids to produce the important lipid second messenger phosphatidic acid. A PLD enzyme expressed by Pseudomonas aeruginosa (PldA) has been shown to be important in bacterial infection, and NAPE-PLD has emerged as being key in the synthesis of endocannabinoids. In order to better understand the biology and therapeutic potential of these less explored PLD enzymes, small molecule tools are required. Selective estrogen receptor modulators (SERMs) have been previously shown to inhibit mammalian PLD (PLD1 and PLD2). By targeted screening of a library of SERM analogues, additional parallel synthesis, and evaluation in multiple PLD assays, we discovered a novel desketoraloxifene-based scaffold that inhibited not only the two mammalian PLDs but also structurally divergent PldA and NAPE-PLD. This finding represents an important first step toward the development of small molecules possessing universal inhibition of divergent PLD enzymes to advance the field.
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Pharmacoeconomics and the medicinal chemist.
ACS Med Chem Lett
PUBLISHED: 10-09-2014
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Pharmacoeconomics is a rational, scientific approach to compare the value (in terms of both cost and patient outcome) of one medication or drug therapy regimen to another. The impact of this new approach on both the practicing medicinal chemist and broader drug discovery efforts is considered.
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Specific activin receptor-like kinase 3 inhibitors enhance liver regeneration.
J. Pharmacol. Exp. Ther.
PUBLISHED: 09-30-2014
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Pharmacologic agents to enhance liver regeneration after injury would have wide therapeutic application. Based on previous work suggesting inhibition of bone morphogenetic protein (BMP) signaling stimulates liver regeneration, we tested known and novel BMP inhibitors for their ability to accelerate regeneration in a partial hepatectomy (PH) model. Compounds were produced based on the 3,6-disubstituted pyrazolo[1,5-a] pyrimidine core of the BMP antagonist dorsomorphin and evaluated for their ability to inhibit BMP signaling and enhance liver regeneration. Antagonists of the BMP receptor activin receptor-like kinase 3 (ALK3), including LDN-193189 (LDN; 4-[6-[4-(1-piperazinyl)phenyl]pyrazolo[1,5-a]pyrimidin-3-yl]-quinoline), DMH2 (4-(2-(4-(3-(quinolin-4-yl)pyrazolo[1,5-a]pyrimidin-6-yl)phenoxy)ethyl)morpholine; VU0364849), and the novel compound VU0465350 (7-(4-isopropoxyphenyl)-3-(1H-pyrazol-4-yl)imidazo[1,2-a]pyridine; VU5350), blocked SMAD phosphorylation in vitro and in vivo, and enhanced liver regeneration after PH. In contrast, an antagonist of the BMP receptor ALK2, VU0469381 (5-(6-(4-methoxyphenyl)pyrazolo[1,5-a]pyrimidin-3-yl)quinolone; 1LWY), did not affect liver regeneration. LDN did not affect liver synthetic or metabolic function. Mechanistically, LDN increased serum interleukin-6 levels and signal transducer and activator of transcription 3 phosphorylation in the liver, and modulated other factors known to be important for liver regeneration, including suppressor of cytokine signaling 3 and p53. These findings suggest that inhibition of ALK3 may be part of a therapeutic strategy for treating human liver disease.
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Phospholipase D signaling pathways and phosphatidic acid as therapeutic targets in cancer.
Pharmacol. Rev.
PUBLISHED: 09-24-2014
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Phospholipase D is a ubiquitous class of enzymes that generates phosphatidic acid as an intracellular signaling species. The phospholipase D superfamily plays a central role in a variety of functions in prokaryotes, viruses, yeast, fungi, plants, and eukaryotic species. In mammalian cells, the pathways modulating catalytic activity involve a variety of cellular signaling components, including G protein-coupled receptors, receptor tyrosine kinases, polyphosphatidylinositol lipids, Ras/Rho/ADP-ribosylation factor GTPases, and conventional isoforms of protein kinase C, among others. Recent findings have shown that phosphatidic acid generated by phospholipase D plays roles in numerous essential cellular functions, such as vesicular trafficking, exocytosis, autophagy, regulation of cellular metabolism, and tumorigenesis. Many of these cellular events are modulated by the actions of phosphatidic acid, and identification of two targets (mammalian target of rapamycin and Akt kinase) has especially highlighted a role for phospholipase D in the regulation of cellular metabolism. Phospholipase D is a regulator of intercellular signaling and metabolic pathways, particularly in cells that are under stress conditions. This review provides a comprehensive overview of the regulation of phospholipase D activity and its modulation of cellular signaling pathways and functions.
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Identification of Positive Allosteric Modulators VU0155094 (ML397) and VU0422288 (ML396) Reveals New Insights into the Biology of Metabotropic Glutamate Receptor 7.
ACS Chem Neurosci
PUBLISHED: 09-17-2014
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Metabotropic glutamate receptor 7 (mGlu7) is a member of the group III mGlu receptors (mGlus), encompassed by mGlu4, mGlu6, mGlu7, and mGlu8. mGlu7 is highly expressed in the presynaptic active zones of both excitatory and inhibitory synapses, and activation of the receptor regulates the release of both glutamate and GABA. mGlu7 is thought to be a relevant therapeutic target for a number of neurological and psychiatric disorders, and polymorphisms in the GRM7 gene have been linked to autism, depression, ADHD, and schizophrenia. Here we report two new pan-group III mGlu positive allosteric modulators, VU0155094 and VU0422288, which show differential activity at the various group III mGlus. Additionally, both compounds show probe dependence when assessed in the presence of distinct orthosteric agonists. By pairing studies of these nonselective compounds with a synapse in the hippocampus that expresses only mGlu7, we have validated activity of these compounds in a native tissue setting. These studies provide proof-of-concept evidence that mGlu7 activity can be modulated by positive allosteric modulation, paving the way for future therapeutics development.
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2013 Philip S. Portoghese Medicinal Chemistry Lectureship: drug discovery targeting allosteric sites.
J. Med. Chem.
PUBLISHED: 09-15-2014
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The identification of sites on receptors topographically distinct from the orthosteric sites, so-called allosteric sites, has heralded novel approaches and modes of pharmacology for target modulation. Over the past 20 years, our understanding of allosteric modulation has grown significantly, and numerous advantages, as well as caveats (e.g., flat structure-activity relationships, species differences, "molecular switches"), have been identified. For multiple receptors and proteins, numerous examples have been described where unprecedented levels of selectivity are achieved along with improved physiochemical properties. While not a panacea, these novel approaches represent exciting opportunities for tool compound development to probe the pharmacology and therapeutic potential of discrete molecular targets, as well as new medicines. In this Perspective, in commemoration of the 2013 Philip S. Portoghese Medicinal Chemistry Lectureship ( Lindsley , C. W. Adventures in allosteric drug discovery . Presented at the 246th National Meeting of the American Chemical Society, Indianapolis, IN, September 10, 2013 ; The 2013 Portoghese Lectureship ), several vignettes of drug discovery campaigns targeting novel allosteric mechanisms will be recounted, along with lessons learned and guidelines that have emerged for successful lead optimization.
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Discovery and Characterization of ML398, a Potent and Selective Antagonist of the D4 Receptor with in Vivo Activity.
ACS Med Chem Lett
PUBLISHED: 09-11-2014
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Herein, we report the structure-activity relationship of a chiral morpholine-based scaffold, which led to the identification of a potent and selective dopamine 4 (D4) receptor antagonist. The 4-chlorobenzyl moiety was identified, and the compound was designated an MLPCN probe molecule, ML398. ML398 is potent against the D4 receptor with IC50 = 130 nM and K i = 36 nM and shows no activity against the other dopamine receptors tested (>20 ?M against D1, D2S, D2L, D3, and D5). Further in vivo studies showed that ML398 reversed cocaine-induced hyperlocomotion at 10 mg/kg.
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Development of a highly potent, novel M5 positive allosteric modulator (PAM) demonstrating CNS exposure: 1-((1H-indazol-5-yl)sulfoneyl)-N-ethyl-N-(2-(trifluoromethyl)benzyl)piperidine-4-carboxamide (ML380).
J. Med. Chem.
PUBLISHED: 09-03-2014
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A functional high throughput screen identified a novel chemotype for the positive allosteric modulation (PAM) of the muscarinic acetylcholine receptor (mAChR) subtype 5 (M5). Application of rapid analog, iterative parallel synthesis efficiently optimized M5 potency to arrive at the most potent M5 PAMs prepared to date and provided tool compound 8n (ML380) demonstrating modest CNS penetration (human M5 EC50 = 190 nM, rat M5 EC50 = 610 nM, brain to plasma ratio (Kp) of 0.36).
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Opportunities and challenges in the discovery of allosteric modulators of GPCRs for treating CNS disorders.
Nat Rev Drug Discov
PUBLISHED: 09-02-2014
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Novel allosteric modulators of G protein-coupled receptors (GPCRs) are providing fundamental advances in the development of GPCR ligands with high subtype selectivity and novel modes of efficacy that have not been possible with traditional approaches. As new allosteric modulators are advancing as drug candidates, we are developing an increased understanding of the major advantages and broad range of activities that can be achieved with these agents through selective modulation of specific signalling pathways, differential effects on GPCR homodimers versus heterodimers, and other properties. This understanding creates exciting opportunities, as well as unique challenges, in the optimization of novel therapeutic agents for disorders of the central nervous system.
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Chemical Modulation of Mutant mGlu1 Receptors Derived from Deleterious GRM1 Mutations Found in Schizophrenics.
ACS Chem. Biol.
PUBLISHED: 08-28-2014
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Schizophrenia is a complex and highly heterogeneous psychiatric disorder whose precise etiology remains elusive. While genome-wide association studies (GWAS) have identified risk genes, they have failed to determine if rare coding single nucleotide polymorphisms (nsSNPs) contribute in schizophrenia. Recently, two independent studies identified 12 rare, deleterious nsSNPS in the GRM1 gene, which encodes the metabotropic glutamate receptor subtype 1 (mGlu1), in schizophrenic patients. Here, we generated stable cell lines expressing the mGlu1 mutant receptors and assessed their pharmacology. Using both the endogenous agonist glutamate and the synthetic agonist DHPG, we found that several of the mutant mGlu1 receptors displayed a loss of function that was not due to a loss in plasma membrane expression. Due to a lack of mGlu1 positive allosteric modulators (PAM) tool compounds active at human mGlu1, we optimized a known mGlu4 PAM/mGlu1 NAM chemotype into a series of potent and selective mGlu1 PAMs by virtue of a double "molecular switch". Employing mGlu1 PAMs from multiple chemotypes, we demonstrate that the mutant receptors can be potentiated by small molecules and in some cases efficacy restored to that comparable to wild type mGlu1 receptors, suggesting deficits in patients with schizophrenia due to these mutations may be amenable to intervention with an mGlu1 PAM. However, in wild type animals, mGlu1 negative allosteric modulators (NAMs) are efficacious in classic models predictive of antipsychotic activity, whereas we show that mGlu1 PAMs have no effect to slight potentiation in these models. These data further highlight the heterogeneity of schizophrenia and the critical role of patient selection strategies in psychiatric clinical trials to match genotype with therapeutic mechanism.
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Selective Activation of M4 Muscarinic Acetylcholine Receptors Reverses MK-801-Induced Behavioral Impairments and Enhances Associative Learning in Rodents.
ACS Chem Neurosci
PUBLISHED: 08-19-2014
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Positive allosteric modulators (PAMs) of the M4 muscarinic acetylcholine receptor (mAChR) represent a novel approach for the treatment of psychotic symptoms associated with schizophrenia and other neuropsychiatric disorders. We recently reported that the selective M4 PAM VU0152100 produced an antipsychotic drug-like profile in rodents after amphetamine challenge. Previous studies suggest that enhanced cholinergic activity may also improve cognitive function and reverse deficits observed with reduced signaling through the N-methyl-d-aspartate subtype of the glutamate receptor (NMDAR) in the central nervous system. Prior to this study, the M1 mAChR subtype was viewed as the primary candidate for these actions relative to the other mAChR subtypes. Here we describe the discovery of a novel M4 PAM, VU0467154, with enhanced in vitro potency and improved pharmacokinetic properties relative to other M4 PAMs, enabling a more extensive characterization of M4 actions in rodent models. We used VU0467154 to test the hypothesis that selective potentiation of M4 receptor signaling could ameliorate the behavioral, cognitive, and neurochemical impairments induced by the noncompetitive NMDAR antagonist MK-801. VU0467154 produced a robust dose-dependent reversal of MK-801-induced hyperlocomotion and deficits in preclinical models of associative learning and memory functions, including the touchscreen pairwise visual discrimination task in wild-type mice, but failed to reverse these stimulant-induced deficits in M4 KO mice. VU0467154 also enhanced the acquisition of both contextual and cue-mediated fear conditioning when administered alone in wild-type mice. These novel findings suggest that M4 PAMs may provide a strategy for addressing the more complex affective and cognitive disruptions associated with schizophrenia and other neuropsychiatric disorders.
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Substituted indoles as selective protease activated receptor 4 (PAR-4) antagonists: Discovery and SAR of ML354.
Bioorg. Med. Chem. Lett.
PUBLISHED: 08-15-2014
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Herein we report the discovery and SAR of an indole-based protease activated receptor-4 (PAR-4) antagonist scaffold derived from a similarity search of the Vanderbilt HTS collection, leading to MLPCN probe ML354 (VU0099704). Using a novel PAC-1 fluorescent ?IIb?3 activation assay this probe molecule antagonist was found to have an IC50 of 140nM for PAR-4 with 71-fold selectivity versus PAR-1 (PAR-1IC50=10?M).
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Discovery of a Highly Selective PLD2 Inhibitor (ML395): A New Probe with Improved Physiochemical Properties and Broad-Spectrum Antiviral Activity against Influenza Strains.
ChemMedChem
PUBLISHED: 08-04-2014
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Further chemical optimization of the halopemide-derived family of dual phospholipase?D1/2 (PLD1/2) inhibitors afforded ML395 (VU0468809), a potent, >80-fold PLD2 selective allosteric inhibitor (cellular PLD1, IC50 >30?000?nM; cellular PLD2, IC50 =360?nM). Moreover, ML395 possesses an attractive in vitro DMPK profile, improved physiochemical properties, ancillary pharmacology (Eurofins Panel) cleaner than any other reported PLD inhibitor, and has been found to possess interesting activity as an antiviral agent in cellular assays against a range of influenza strains (H1, H3, H5 and H7).
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Phospholipase D facilitates efficient entry of influenza virus, allowing escape from innate immune inhibition.
J. Biol. Chem.
PUBLISHED: 07-27-2014
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Lipid metabolism plays a fundamental role during influenza virus replication, although key regulators of lipid-dependent trafficking and virus production remain inadequately defined. This report demonstrates that infection by influenza virus stimulates phospholipase D (PLD) activity and that PLD co-localizes with influenza during infection. Both chemical inhibition and RNA interference of PLD delayed viral entry and reduced viral titers in vitro. Although there may be contributions by both major isoenzymes, the effects on viral infectivity appear to be more dependent on the PLD2 isoenzyme. In vivo, PLD2 inhibition reduced virus titer and correlated with significant increases in transcription of innate antiviral effectors. The reduction in viral titer downstream of PLD2 inhibition was dependent on Rig-I (retinoic acid-inducible gene-1), IRF3, and MxA (myxovirus resistance gene A) but not IRF7. Inhibition of PLD2 accelerated the accumulation of MxA in foci as early as 30 min postinfection. Together these data suggest that PLD facilitates the rapid endocytosis of influenza virus, permitting viral escape from innate immune detection and effectors that are capable of limiting lethal infection.
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Discovery of potent and selective GIRK1/2 modulators via 'molecular switches' within a series of 1-(3-cyclopropyl-1-phenyl-1H-pyrazol-5-yl)ureas.
Bioorg. Med. Chem. Lett.
PUBLISHED: 07-07-2014
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This Letter describes the on-going SAR efforts based on ML297, a potent, efficacious and selective GIRK1/2 activator (?10-fold vs GIRK1/4 and inactive on GIRK2/3) via an iterative parallel synthesis approach. The chemical optimization at the 3-position of pyrazole within ML297 indicated that various functionalized 3-cyclopropyl moieties modulated GIRK pharmacology between inhibitor/activator within a series of 1-(3-cyclopropyl-1-phenyl-1H-pyrazol-5-yl)ureas. Importantly, novel 'molecular switches' that modulated the mode of pharmacology from inhibitor to activator was discovered on both the 3-cyclopropyl and N-phenyl moiety of the pyrazole core, providing the first highly selective GIRK1/2 activator.
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Discovery and Characterization of 2-(Cyclopropanesulfonamido)-N-(2-ethoxyphenyl)benzamide, ML382: a Potent and Selective Positive Allosteric Modulator of MrgX1.
ChemMedChem
PUBLISHED: 07-07-2014
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Previous studies have shown that the activation of mouse MrgC11, a G-protein-coupled receptor, by its peptide ligand BAM8-22 can inhibit chronic pain. A large-scale screen has been carried out to isolate small-molecule allosteric agonists of MrgX1, the human homologue of MrgC11. The goal of this study is to improve the efficacy and potency of positive allosteric modulators (PAMs) with therapeutic implications in combating chronic pain. Herein we report an iterative parallel synthesis effort and a structure-activity relationship study of a series of arylsulfonamides which led to the discovery of the first PAM of MrgX1, ML382.
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Tetrahydronaphthyridine and dihydronaphthyridinone ethers as positive allosteric modulators of the metabotropic glutamate receptor 5 (mGlu?).
J. Med. Chem.
PUBLISHED: 06-25-2014
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Positive allosteric modulators (PAMs) of metabotropic glutamate receptor 5 (mGlu5) represent a promising therapeutic strategy for the treatment of schizophrenia. Starting from an acetylene-based lead from high throughput screening, an evolved bicyclic dihydronaphthyridinone was identified. We describe further refinements leading to both dihydronaphthyridinone and tetrahydronaphthyridine mGlu5 PAMs containing an alkoxy-based linkage as an acetylene replacement. Exploration of several structural features including western pyridine ring isomers, positional amides, linker connectivity/position, and combinations thereof, reveal that these bicyclic modulators generally exhibit steep SAR and within specific subseries display a propensity for pharmacological mode switching at mGlu5 as well as antagonist activity at mGlu3. Structure-activity relationships within a dihydronaphthyridinone subseries uncovered 12c (VU0405372), a selective mGlu5 PAM with good in vitro potency, low glutamate fold-shift, acceptable DMPK properties, and in vivo efficacy in an amphetamine-based model of psychosis.
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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.
ACS Chem Neurosci
PUBLISHED: 05-15-2014
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Recent progress in the discovery of mGlu? allosteric modulators has suggested the modulation of mGlu? 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 mGlu? 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 mGlu? negative allosteric modulator hits for chemical optimization. Herein, we describe the discovery and characterization of a novel mGlu? chemotype. This series of succinimide negative allosteric modulators, exemplified by VU0410425, exhibited potent inhibitory activity at rat mGlu? but was, surprisingly, inactive at human mGlu?. VU0410425 and a set of chemically diverse mGlu? negative allosteric modulators previously reported in the literature were utilized to examine this species disconnect between rat and human mGlu? 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 mGlu? negative allosteric modulators provides valuable insight into the pharmacology underlying the disconnect between rat and human mGlu? activity, an issue that must be understood to progress the therapeutic potential of allosteric modulators of mGlu?.
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Relationship between In Vivo Receptor Occupancy and Efficacy of Metabotropic Glutamate Receptor Subtype 5 Allosteric Modulators with Different In Vitro Binding Profiles.
Neuropsychopharmacology
PUBLISHED: 05-14-2014
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Allosteric modulators of the metabotropic glutamate receptor subtype 5 (mGlu5) have exciting potential as therapeutic agents for multiple brain disorders. Translational studies with mGlu5 modulators have relied on mGlu5 allosteric site positron emission tomography (PET) radioligands to assess receptor occupancy in the brain. However, recent structural and modeling studies suggest that closely related mGlu5 allosteric modulators can bind to overlapping but not identical sites, which could complicate interpretation of in vivo occupancy data, even when PET ligands and drug leads are developed from the same chemical scaffold. We now report that systemic administration of the novel mGlu5 positive allosteric modulator VU0092273 displaced the structurally related mGlu5 PET ligand, [(18)F]FPEB, with measures of in vivo occupancy that closely aligned with its in vivo efficacy. In contrast, a close analog of VU0092273 and [(18)F]FPEB, VU0360172, provided robust efficacy in rodent models in the absence of detectable occupancy. Furthermore, a structurally unrelated mGlu5 negative allosteric modulator, VU0409106, displayed measures of in vivo occupancy that correlated well with behavioral effects, despite the fact that VU0409106 is structurally unrelated to [(18)F]FPEB. Interestingly, all three compounds inhibit radioligand binding to the prototypical MPEP/FPEB allosteric site in vitro. However, VU0092273 and VU0409106 bind to this site in a fully competitive manner, whereas the interaction of VU0360172 is noncompetitive. Thus, while close structural similarity between PET ligands and drug leads does not circumvent issues associated with differential binding to a given target, detailed molecular pharmacology analysis accurately predicts utility of ligand pairs for in vivo occupancy studies.Neuropsychopharmacology advance online publication, 22 October 2014; doi:10.1038/npp.2014.245.
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Discovery of VU0431316: a negative allosteric modulator of mGlu5 with activity in a mouse model of anxiety.
Bioorg. Med. Chem. Lett.
PUBLISHED: 04-30-2014
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Development of SAR in an aryl ether series of mGlu5 NAMs leading to the identification of pyrazine analog VU0431316 is described in this Letter. VU0431316 is a potent and selective non-competitive antagonist of mGlu5 that binds at a known allosteric binding site. VU0431316 demonstrates an attractive DMPK profile, including moderate clearance and good bioavailability in rats. Intraperitoneal (IP) dosing of VU0431316 in a mouse marble burying model of anxiety, an assay known to be sensitive to mGlu5 antagonists and other anxiolytics, produced dose proportional effects.
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Synthesis and SAR of substituted pyrazolo[1,5-a]quinazolines as dual mGlu(2)/mGlu(3) NAMs.
Bioorg. Med. Chem. Lett.
PUBLISHED: 03-25-2014
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Herein we report the design and synthesis of a series of substituted pyrazolo[1,5-a]quinazolin-5(4H)-ones as negative allosteric modulators of metabotropic glutamate receptors 2 and 3 (mGlu2 and mGlu3, respectively). Development of this series was initiated by reports that pyrazolo[1,5-a]quinazoline-derived scaffolds can yield compounds with activity at group II mGlu receptors which are prone to molecular switching following small structural changes. Several potent analogues, including 4-methyl-2-phenyl-8-(pyrimidin-5-yl)pyrazolo[1,5-a]quinazolin-5(4H)-one (10b), were discovered with potent in vitro activity as dual mGlu2/mGlu3 NAMs, with excellent selectivity versus the other mGluRs.
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Discovery and SAR of a novel series of metabotropic glutamate receptor 5 positive allosteric modulators with high ligand efficiency.
Bioorg. Med. Chem. Lett.
PUBLISHED: 03-24-2014
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We report the optimization of a series of novel metabotropic glutamate receptor 5 (mGlu5) positive allosteric modulators (PAMs) from a 5,6-bicyclic class of dihydropyrazolo[1,5-a]pyridin-4(5H)-ones containing a phenoxymethyl linker. Studies focused on a survey of non-amide containing hydrogen bond accepting (HBA) pharmacophore replacements. A highly potent and selective PAM, 2-(phenoxymethyl)-6,7-dihydropyrazolo[1,5-a]pyridin-4(5H)-one (11, VU0462054), bearing a simple ketone moiety, was identified (LE=0.52, LELP=3.2). In addition, hydroxyl, difluoro, ether, and amino variations were examined. Despite promising lead properties and exploration of alternative core heterocycles, linkers, and ketone replacements, oxidative metabolism and in vivo clearance remained problematic for the series.
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Discovery, synthesis and characterization of a highly muscarinic acetylcholine receptor (mAChR)-selective M5-orthosteric antagonist, VU0488130 (ML381): a novel molecular probe.
ChemMedChem
PUBLISHED: 02-28-2014
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Of the five G-protein-coupled muscarinic acetylcholine receptors (mAChRs; M1-M5), M5 is the least explored and understood due to a lack of mAChR subtype-selective ligands. We recently performed a high-throughput functional screen and identified a number of weak antagonist hits that are selective for the M5 receptor. Here, we report an iterative parallel synthesis and detailed molecular pharmacologic profiling effort that led to the discovery of the first highly selective, central nervous system (CNS)-penetrant M5-orthosteric antagonist, with sub-micromolar potency (hM5 IC50=450?nM, hM5 Ki=340?nM, M1-M4 IC50>30??M), enantiospecific inhibition, and an acceptable drug metabolism and pharmacokinetics (DMPK) profile for in vitro and electrophysiology studies. This compound will be a powerful tool and molecular probe for the further investigation into the role of M5 in addiction and other diseases.
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M5 receptor activation produces opposing physiological outcomes in dopamine neurons depending on the receptor's location.
J. Neurosci.
PUBLISHED: 02-28-2014
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Of the five muscarinic receptor subtypes, the M5 receptor is the only one detectable in midbrain dopaminergic neurons, making it an attractive potential therapeutic target for treating disorders in which dopaminergic signaling is disrupted. However, developing an understanding of the role of M5 in regulating midbrain dopamine neuron function has been hampered by a lack of subtype-selective compounds. Here, we extensively characterize the novel compound VU0238429 and demonstrate that it acts as a positive allosteric modulator with unprecedented selectivity for the M5 receptor. We then used VU0238429, along with M5 knock-out mice, to elucidate the role of this receptor in regulating substantia nigra pars compacta (SNc) neuron physiology in both mice and rats. In sagittal brain slices that isolate the SNc soma from their striatal terminals, activation of muscarinic receptors induced Ca2+ mobilization and inward currents in SNc dopamine neurons, both of which were potentiated by VU0238429 and absent in M5 knock-out mice. Activation of M5 also increased the spontaneous firing rate of SNc neurons, suggesting that activation of somatodendritic M5 increases the intrinsic excitability of SNc neurons. However, in coronal slices of the striatum, potentiation of M5 with VU0238429 resulted in an inhibition in dopamine release as monitored with fast scan cyclic voltammetry. Accordingly, activation of M5 can lead to opposing physiological outcomes depending on the location of the receptor. Although activation of somatodendritic M5 receptors on SNc neurons leads to increased neuronal firing, activation of M5 receptors in the striatum induces an inhibition in dopamine release.
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M4 mAChR-mediated modulation of glutamatergic transmission at corticostriatal synapses.
ACS Chem Neurosci
PUBLISHED: 02-27-2014
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The striatum is the main input station of the basal ganglia and is extensively involved in the modulation of motivated behavior. The information conveyed to this subcortical structure through glutamatergic projections from the cerebral cortex and thalamus is processed by the activity of several striatal neuromodulatory systems including the cholinergic system. Acetylcholine potently modulates glutamate signaling in the striatum via activation of muscarinic receptors (mAChRs). It is, however, unclear which mAChR subtype is responsible for this modulatory effect. Here, by using electrophysiological, optogenetic, and immunoelectron microscopic approaches in conjunction with a novel, highly selective M4 positive allosteric modulator VU0152100 (ML108) and M4 knockout mice, we show that M4 is a major mAChR subtype mediating the cholinergic inhibition of corticostriatal glutamatergic input on both striatonigral and striatopallidal medium spiny neurons (MSNs). This effect is due to activation of presynaptic M4 receptors, which, in turn, leads to a decrease in glutamate release from corticostriatal terminals. The findings of the present study raise the interesting possibility that M4 mAChR could be a novel therapeutic target for the treatment of neurological and neuropsychiatric disorders involving hyper-glutamatergic transmission at corticostriatal synapses.
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Identification of specific ligand-receptor interactions that govern binding and cooperativity of diverse modulators to a common metabotropic glutamate receptor 5 allosteric site.
ACS Chem Neurosci
PUBLISHED: 02-26-2014
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A common metabotropic glutamate receptor 5 (mGlu5) allosteric site is known to accommodate diverse chemotypes. However, the structural relationship between compounds from different scaffolds and mGlu5 is not well understood. In an effort to better understand the molecular determinants that govern allosteric modulator interactions with mGlu5, we employed a combination of site-directed mutagenesis and computational modeling. With few exceptions, six residues (P654, Y658, T780, W784, S808, and A809) were identified as key affinity determinants across all seven allosteric modulator scaffolds. To improve our interpretation of how diverse allosteric modulators occupy the common allosteric site, we sampled the wealth of mGlu5 structure-activity relationship (SAR) data available by docking 60 ligands (actives and inactives) representing seven chemical scaffolds into our mGlu5 comparative model. To spatially and chemically compare binding modes of ligands from diverse scaffolds, the ChargeRMSD measure was developed. We found a common binding mode for the modulators that placed the long axes of the ligands parallel to the transmembrane helices 3 and 7. W784 in TM6 not only was identified as a key NAM cooperativity determinant across multiple scaffolds, but also caused a NAM to PAM switch for two different scaffolds. Moreover, a single point mutation in TM5, G747V, altered the architecture of the common allosteric site such that 4-nitro-N-(1,3-diphenyl-1H-pyrazol-5-yl)benzamide (VU29) was noncompetitive with the common allosteric site. Our findings highlight the subtleties of allosteric modulator binding to mGlu5 and demonstrate the utility in incorporating SAR information to strengthen the interpretation and analyses of docking and mutational data.
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A Duplexed High-Throughput Screen to Identify Allosteric Modulators of the Glucagon-Like Peptide 1 and Glucagon Receptors.
J Biomol Screen
PUBLISHED: 02-13-2014
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Injectable, degradation-resistant peptide agonists for the glucagon-like peptide 1 (GLP-1) receptor (GLP-1R), such as exenatide and liraglutide, activate the GLP-1R via a complex orthosteric-binding site and are effective therapeutics for glycemic control in type 2 diabetes. Orally bioavailable orthosteric small-molecule agonists are unlikely to be developed, whereas positive allosteric modulators (PAMs) may offer an improved therapeutic profile. We hypothesize that allosteric modulators of the GLP-1R would increase the potency and efficacy of native GLP-1 in a spatial and temporally preserved manner and/or may improve efficacy or side effects of injectable analogs. We report the design, optimization, and initial results of a duplexed high-throughput screen in which cell lines overexpressing either the GLP-1R or the glucagon receptor were coplated, loaded with a calcium-sensitive dye, and probed in a three-phase assay to identify agonists, antagonists, and potentiators of GLP-1, and potentiators of glucagon. 175,000 compounds were initially screened, and progression through secondary assays yielded 98 compounds with a variety of activities at the GLP-1R. Here, we describe five compounds possessing different patterns of modulation of the GLP-1R. These data uncover PAMs that may offer a drug-development pathway to enhancing in vivo efficacy of both endogenous GLP-1 and peptide analogs.
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High-affinity small-molecule inhibitors of the menin-mixed lineage leukemia (MLL) interaction closely mimic a natural protein-protein interaction.
J. Med. Chem.
PUBLISHED: 02-06-2014
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The protein-protein interaction (PPI) between menin and mixed lineage leukemia (MLL) plays a critical role in acute leukemias, and inhibition of this interaction represents a new potential therapeutic strategy for MLL leukemias. We report development of a novel class of small-molecule inhibitors of the menin-MLL interaction, the hydroxy- and aminomethylpiperidine compounds, which originated from HTS of ?288000 small molecules. We determined menin-inhibitor co-crystal structures and found that these compounds closely mimic all key interactions of MLL with menin. Extensive crystallography studies combined with structure-based design were applied for optimization of these compounds, resulting in MIV-6R, which inhibits the menin-MLL interaction with IC50 = 56 nM. Treatment with MIV-6 demonstrated strong and selective effects in MLL leukemia cells, validating specific mechanism of action. Our studies provide novel and attractive scaffold as a new potential therapeutic approach for MLL leukemias and demonstrate an example of PPI amenable to inhibition by small molecules.
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Antipsychotic drug-like effects of the selective M4 muscarinic acetylcholine receptor positive allosteric modulator VU0152100.
Neuropsychopharmacology
PUBLISHED: 01-20-2014
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Accumulating evidence suggests that selective M4 muscarinic acetylcholine receptor (mAChR) activators may offer a novel strategy for the treatment of psychosis. However, previous efforts to develop selective M4 activators were unsuccessful because of the lack of M4 mAChR subtype specificity and off-target muscarinic adverse effects. We recently developed VU0152100, a highly selective M4 positive allosteric modulator (PAM) that exerts central effects after systemic administration. We now report that VU0152100 dose-dependently reverses amphetamine-induced hyperlocomotion in rats and wild-type mice, but not in M4 KO mice. VU0152100 also blocks amphetamine-induced disruption of the acquisition of contextual fear conditioning and prepulse inhibition of the acoustic startle reflex. These effects were observed at doses that do not produce catalepsy or peripheral adverse effects associated with non-selective mAChR agonists. To further understand the effects of selective potentiation of M4 on region-specific brain activation, VU0152100 alone and in combination with amphetamine were evaluated using pharmacologic magnetic resonance imaging (phMRI). Key neural substrates of M4-mediated modulation of the amphetamine response included the nucleus accumbens (NAS), caudate-putamen (CP), hippocampus, and medial thalamus. Functional connectivity analysis of phMRI data, specifically assessing correlations in activation between regions, revealed several brain networks involved in the M4 modulation of amphetamine-induced brain activation, including the NAS and retrosplenial cortex with motor cortex, hippocampus, and medial thalamus. Using in vivo microdialysis, we found that VU0152100 reversed amphetamine-induced increases in extracellular dopamine levels in NAS and CP. The present data are consistent with an antipsychotic drug-like profile of activity for VU0152100. Taken together, these data support the development of selective M4 PAMs as a new approach to the treatment of psychosis and cognitive impairments associated with psychiatric disorders such as schizophrenia.
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Chemical modulation of glycerolipid signaling and metabolic pathways.
Biochim. Biophys. Acta
PUBLISHED: 01-06-2014
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Thirty years ago, glycerolipids captured the attention of biochemical researchers as novel cellular signaling entities. We now recognize that these biomolecules occupy signaling nodes critical to a number of physiological and pathological processes. Thus, glycerolipid-metabolizing enzymes present attractive targets for new therapies. A number of fields-ranging from neuroscience and cancer to diabetes and obesity-have elucidated the signaling properties of glycerolipids. The biochemical literature teems with newly emerging small molecule inhibitors capable of manipulating glycerolipid metabolism and signaling. This ever-expanding pool of chemical modulators appears daunting to those interested in exploiting glycerolipid-signaling pathways in their model system of choice. This review distills the current body of literature surrounding glycerolipid metabolism into a more approachable format, facilitating the application of small molecule inhibitors to novel systems. This article is part of a Special Issue entitled Tools to study lipid functions.
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Novel GlyT1 inhibitor chemotypes by scaffold hopping. Part 2: development of a [3.3.0]-based series and other piperidine bioisosteres.
Bioorg. Med. Chem. Lett.
PUBLISHED: 01-02-2014
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This Letter describes the development and SAR of a novel series of GlyT1 inhibitors derived from a scaffold hopping approach, in lieu of an HTS campaign, which provided intellectual property position. Members within this new [3.3.0]-based series displayed excellent GlyT1 potency, selectivity, free fraction, and modest CNS penetration. Moreover, enantioselective GlyT1 inhibition was observed, within this novel series and a number of other piperidine bioisosteric cores.
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Novel GlyT1 inhibitor chemotypes by scaffold hopping. Part 1: development of a potent and CNS penetrant [3.1.0]-based lead.
Bioorg. Med. Chem. Lett.
PUBLISHED: 01-02-2014
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This Letter describes the development and SAR of a novel series of GlyT1 inhibitors derived from a scaffold hopping approach that provided a robust intellectual property position, in lieu of a traditional, expensive HTS campaign. Members within this new [3.1.0]-based series displayed excellent GlyT1 potency, selectivity, free fraction, CNS penetration and efficacy in a preclinical model of schizophrenia (prepulse inhibition).
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Phospholipase D2 mediates survival signaling through direct regulation of Akt in glioblastoma cells.
J. Biol. Chem.
PUBLISHED: 11-20-2013
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The lack of innovative drug targets for glioblastoma multiforme (GBM) limits patient survival to approximately one year following diagnosis. The pro-survival kinase Akt provides an ideal target for the treatment of GBM as Akt signaling is frequently activated in this cancer type. However, the central role of Akt in physiological processes limits its potential as a therapeutic target. In this report we show that the lipid metabolizing enzyme phospholipase D (PLD) is a novel regulator of Akt in GBM. Studies using a combination of small molecule PLD inhibitors and siRNA knockdowns establish phosphatidic acid (PtdOH), the product of the PLD reaction, as an essential component for the membrane recruitment and activation of Akt. Inhibition of PLD enzymatic activity and subsequent Akt activation decreases GBM cell viability by specifically inhibiting autophagic flux. We propose a mechanism whereby phosphorylation of Beclin1 by Akt prevents binding of Rubicon, an interaction known to inhibit autophagic flux. These findings provide a novel framework through which Akt inhibition can be achieved without directly targeting the kinase.
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Metabotropic glutamate receptor 5-positive allosteric modulators for the treatment of schizophrenia (2004-2012).
Pharm Pat Anal
PUBLISHED: 11-19-2013
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The mGlu5, a class C G-protein-coupled receptor and member of the group I mGlu receptor family, has been demonstrated to play a role in a number of therapeutic areas within the CNS, including schizophrenia, dementia, epilepsy, cognition, drug abuse, and fragile X syndrome. Small-molecule modulation of mGlu5 via positive allosteric modulators (PAMs) is being pursued as a promising approach for the treatment of schizophrenia and has been validated preclinically in a number of animal models. This article provides a brief historical overview of mGlu5 PAMs in the primary literature followed by a comprehensive overview of the patent literature since 2004. Schizophrenia is a complex disorder and although no mGlu5 PAMs have progressed into clinical trials in patients, the target continues to show promise as an attractive non-dopaminergic therapy. The successful development of mGlu5 PAMs for clinical testing must address several issues, including challenges associated with molecular switches, allosteric-agonist activity and stimulus bias.
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Discovery of the First M5-Selective and CNS Penetrant Negative Allosteric Modulator (NAM) of a Muscarinic Acetylcholine Receptor: (S)-9b-(4-Chlorophenyl)-1-(3,4-difluorobenzoyl)-2,3-dihydro-1H-imidazo[2,1-a]isoindol-5(9bH)-one (ML375).
J. Med. Chem.
PUBLISHED: 11-13-2013
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A functional high throughput screen and subsequent multidimensional, iterative parallel synthesis effort identified the first muscarinic acetylcholine receptor (mAChR) negative allosteric modulator (NAM) selective for the M5 subtype. ML375 is a highly selective M5 NAM with submicromolar potency (human M5 IC50 = 300 nM, rat M5 IC50 = 790 nM, M1-M4 IC50 > 30 ?M), excellent multispecies PK, high CNS penetration, and enantiospecific inhibition.
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Glycine transporter-1 inhibition promotes striatal axon sprouting via NMDA receptors in dopamine neurons.
J. Neurosci.
PUBLISHED: 10-18-2013
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NMDA receptor activity is involved in shaping synaptic connections throughout development and adulthood. We recently reported that brief activation of NMDA receptors on cultured ventral midbrain dopamine neurons enhanced their axon growth rate and induced axonal branching. To test whether this mechanism was relevant to axon regrowth in adult animals, we examined the reinnervation of dorsal striatum following nigral dopamine neuron loss induced by unilateral intrastriatal injections of the toxin 6-hydroxydopamine. We used a pharmacological approach to enhance NMDA receptor-dependent signaling by treatment with an inhibitor of glycine transporter-1 that elevates levels of extracellular glycine, a coagonist required for NMDA receptor activation. All mice displayed sprouting of dopaminergic axons from spared fibers in the ventral striatum to the denervated dorsal striatum at 7 weeks post-lesion, but the reinnervation in mice treated for 4 weeks with glycine uptake inhibitor was approximately twice as dense as in untreated mice. The treated mice also displayed higher levels of striatal dopamine and a complete recovery from lateralization in a test of sensorimotor behavior. We confirmed that the actions of glycine uptake inhibition on reinnervation and behavioral recovery required NMDA receptors in dopamine neurons using targeted deletion of the NR1 NMDA receptor subunit in dopamine neurons. Glycine transport inhibitors promote functionally relevant sprouting of surviving dopamine axons and could provide clinical treatment for disorders such as Parkinsons disease.
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Exploration of Allosteric Agonism Structure-Activity Relationships within an Acetylene Series of Metabotropic Glutamate Receptor 5 (mGlu5) Positive Allosteric Modulators (PAMs): Discovery of 5-((3-Fluorophenyl)ethynyl)-N-(3-methyloxetan-3-yl)picolinamide
J. Med. Chem.
PUBLISHED: 10-09-2013
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Positive allosteric modulators (PAMs) of metabotropic glutamate receptor 5 (mGlu5) represent a promising therapeutic strategy for the treatment of schizophrenia. Both allosteric agonism and high glutamate fold-shift have been implicated in the neurotoxic profile of some mGlu5 PAMs; however, these hypotheses remain to be adequately addressed. To develop tool compounds to probe these hypotheses, the structure-activity relationship of allosteric agonism was examined within an acetylenic series of mGlu5 PAMs exhibiting allosteric agonism in addition to positive allosteric modulation (ago-PAMs). PAM 38t, a low glutamate fold-shift allosteric ligand (maximum fold-shift ?3.0), was selected as a potent PAM with no agonism in the in vitro system used for compound characterization and in two native electrophysiological systems using rat hippocampal slices. PAM 38t (ML254) will be useful to probe the relative contribution of cooperativity and allosteric agonism to the adverse effect liability and neurotoxicity associated with this class of mGlu5 PAMs.
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Drugs for Allosteric Sites on Receptors.
Annu. Rev. Pharmacol. Toxicol.
PUBLISHED: 10-02-2013
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The presence of druggable, topographically distinct allosteric sites on a wide range of receptor families has offered new paradigms for small molecules to modulate receptor function. Moreover, ligands that target allosteric sites offer significant advantages over the corresponding orthosteric ligands in terms of selectivity, including subtype selectivity within receptor families, and can also impart improved physicochemical properties. However, allosteric ligands are not a panacea. Many chemical issues (e.g., flat structure-activity relationships) and pharmacological issues (e.g., ligand-biased signaling) that are allosteric centric have emerged. Notably, the fact that allosteric sites are less evolutionarily conserved leads to improved selectivity; however, this can also lead to species differences that can hinder safety assessment. Many allosteric ligands possess molecular switches, wherein a small structural change (chemical or metabolic) can modulate the mode of pharmacology or receptor subtype selectivity. As the field has matured, as described here, key principles and strategies have emerged for the design of ligands/drugs for allosteric sites. Expected final online publication date for the Annual Review of Pharmacology and Toxicology Volume 54 is January 06, 2014. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
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Allosteric modulation of Class C GPCRs: a novel approach for the treatment of CNS disorders.
Drug Discov Today Technol
PUBLISHED: 09-21-2013
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Allosteric modulation has emerged as an innovative pharmacological approach to selectively activate or inhibit several Class C GPCRs. Of the Class C GPCRs, metabotropic glutamate (mGlu) receptors represent the most promising candidates for clinical success, and both positive allosteric modulators (PAMs) and negative allosteric modulators (NAMs) of mGluRs have demonstrated therapeutic potential for a range of psychiatric and neurological disorders such as pain, depression, anxiety, cognition, Fragile X syndrome, Parkinson’s disease and schizophrenia.
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Classics in chemical neuroscience: clozapine.
ACS Chem Neurosci
PUBLISHED: 09-20-2013
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Clozapine was the first true breakthrough in schizophrenia treatment since the discovery of chlorpromazine in 1950, effectively treating positive, negative, and some cognitive symptoms, as well as possessing unprecedented efficacy in treatment-resistant patients. Despite over 30 years of intense study, the precise molecular underpinnings that account for clozapines unique efficacy remain elusive. In this Viewpoint, we will showcase the history and importance of clozapine to neuroscience in general, as well as for the treatment of schizophrenia, and review the synthesis, pharmacology, drug metabolism, and adverse events of clozapine.
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A general, enantioselective synthesis of ?- and ?-fluoroamines.
Tetrahedron Lett.
PUBLISHED: 09-17-2013
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In this Letter, we describe a short, high yielding protocol for the enantioselective (87-96% ee) and general synthesis of ?-fluoroamines and previously difficult to access ?-fluoroamines from commercial aldehydes via organocatalysis.
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Dihydrothiazolopyridone derivatives as a novel family of positive allosteric modulators of the metabotropic glutamate 5 (mGlu5) receptor.
J. Med. Chem.
PUBLISHED: 09-04-2013
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Starting from a singleton chromanone high throughput screening (HTS) hit, we describe a focused medicinal chemistry optimization effort leading to the identification of a novel series of phenoxymethyl-dihydrothiazolopyridone derivatives as selective positive allosteric modulators (PAMs) of the metabotropic glutamate 5 (mGlu5) receptor. These dihydrothiazolopyridones potentiate receptor responses in recombinant systems. In vitro and in vivo drug metabolism and pharmacokinetic (DMPK) evaluation allowed us to select compound 16a for its assessment in a preclinical animal screen of possible antipsychotic activity. 16a was able to reverse amphetamine-induced hyperlocomotion in rats in a dose-dependent manner without showing any significant motor impairment or overt neurological side effects at comparable doses. Evolution of our medicinal chemistry program, structure activity, and properties relationships (SAR and SPR) analysis as well as a detailed profile for optimized mGlu5 receptor PAM 16a are described.
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Heterotropic activation of the midazolam hydroxylase activity of CYP3A by a positive allosteric modulator of mGlu5: in vitro to in vivo translation and potential impact on clinically relevant drug-drug interactions.
Drug Metab. Dispos.
PUBLISHED: 09-03-2013
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Allosteric modulation of G protein-coupled receptors has gained considerable attention in the drug discovery arena because it opens avenues to achieve greater selectivity over orthosteric ligands. We recently identified a series of positive allosteric modulators (PAMs) of metabotropic glutamate receptor 5 (mGlu(5)) for the treatment of schizophrenia that exhibited robust heterotropic activation of CYP3A4 enzymatic activity. The prototypical compound from this series, 5-(4-fluorobenzyl)-2-((3-fluorophenoxy)methyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine (VU0448187), was found to activate CYP3A4 to >100% of its baseline intrinsic midazolam (MDZ) hydroxylase activity in vitro; activation was CYP3A substrate specific and mGlu(5) PAM dependent. Additional studies revealed the concentration-dependence of CYP3A activation by VU0448187 in multispecies hepatic and intestinal microsomes and hepatocytes, as well as a diminished effect observed in the presence of ketoconazole. Kinetic analyses of the effect of VU0448187 on MDZ metabolism in recombinant P450 or human liver microsomes resulted in a significant increase in V(max) (minimal change in K(m)) and required the presence of cytochrome b5. The atypical kinetics translated in vivo, as rats receiving an intraperitoneal administration of VU0448187 prior to MDZ treatment demonstrated a significant increase in circulating 1- and 4-hydroxy- midazolam (1-OH-MDZ, 4-OH-MDZ) levels compared with rats administered MDZ alone. The discovery of a potent substrate-selective activator of rodent CYP3A with an in vitro to in vivo translation serves to illuminate the impact of increasing intrinsic enzymatic activity of hepatic and extrahepatic CYP3A in rodents, and presents the basis to build models capable of framing the clinical relevance of substrate-dependent heterotropic activation.
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Reversible inhibitors of regulators of G-protein signaling identified in a high-throughput cell-based calcium signaling assay.
Cell. Signal.
PUBLISHED: 08-20-2013
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Regulator of G-protein signaling (RGS) proteins potently suppress G-protein coupled receptor (GPCR) signal transduction by accelerating GTP hydrolysis on activated heterotrimeric G-protein ? subunits. RGS4 is enriched in the CNS and is proposed as a therapeutic target for treatment of neuropathological states including epilepsy and Parkinsons disease. Therefore, identification of novel RGS4 inhibitors is of interest. An HEK293-FlpIn cell-line stably expressing M3-muscarinic receptor with doxycycline-regulated RGS4 expression was employed to identify compounds that inhibit RGS4-mediated suppression of M3-muscarinic receptor signaling. Over 300,000 compounds were screened for an ability to enhance G?q-mediated calcium signaling in the presence of RGS4. Compounds that modulated the calcium response in a counter-screen in the absence of RGS4 were not pursued. Of the 1365 RGS4-dependent primary screen hits, thirteen compounds directly target the RGS-G-protein interaction in purified systems. All thirteen compounds lose activity against an RGS4 mutant lacking cysteines, indicating that covalent modification of free thiol groups on RGS4 is a common mechanism. Four compounds produce >85% inhibition of RGS4-G-protein binding at 100?M, yet are >50% reversible within a ten-minute time frame. The four reversible compounds significantly alter the thermal melting temperature of RGS4, but not G-protein, indicating that inhibition is occurring through interaction with the RGS protein. The HEK cell-line employed for this study provides a powerful tool for efficiently identifying RGS-specific modulators within the context of a GPCR signaling pathway. As a result, several new reversible, cell-active RGS4 inhibitors have been identified for use in future biological studies.
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Discovery of VU0409106: A negative allosteric modulator of mGlu5 with activity in a mouse model of anxiety.
Bioorg. Med. Chem. Lett.
PUBLISHED: 08-09-2013
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Development of SAR in an aryl ether series of mGlu5 NAMs leading to the identification of tool compound VU0409106 is described in this Letter. VU0409106 is a potent and selective negative allosteric modulator of mGlu5 that binds at the known allosteric binding site and demonstrates good CNS exposure following intraperitoneal dosing in mice. VU0409106 also proved efficacious in a mouse marble burying model of anxiety, an assay known to be sensitive to mGlu5 antagonists as well as clinically efficacious anxiolytics.
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Potentiating mGluR5 function with a positive allosteric modulator enhances adaptive learning.
Learn. Mem.
PUBLISHED: 07-23-2013
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Metabotropic glutamate receptor 5 (mGluR5) plays important roles in modulating neural activity and plasticity and has been associated with several neuropathological disorders. Previous work has shown that genetic ablation or pharmacological inhibition of mGluR5 disrupts fear extinction and spatial reversal learning, suggesting that mGluR5 signaling is required for different forms of adaptive learning. Here, we tested whether ADX47273, a selective positive allosteric modulator (PAM) of mGluR5, can enhance adaptive learning in mice. We found that systemic administration of the ADX47273 enhanced reversal learning in the Morris Water Maze, an adaptive task. In addition, we found that ADX47273 had no effect on single-session and multi-session extinction, but administration of ADX47273 after a single retrieval trial enhanced subsequent fear extinction learning. Together these results demonstrate a role for mGluR5 signaling in adaptive learning, and suggest that mGluR5 PAMs represent a viable strategy for treatment of maladaptive learning and for improving behavioral flexibility.
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Total Synthesis of Stemaphylline N-Oxide and Related C9a-Epimeric Analogues.
Chemistry
PUBLISHED: 07-09-2013
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Winning the relay: The first total synthesis of stemaphylline N-oxide has been completed utilizing a bistandem relay ring-closing-metathesis (RRCM) strategy, necessitated by the conformation of the requisite tetraene. This effort also gave unnatural 9a-epi-stemaphylline and 9a-epi-stemaphylline N-oxide.
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Discovery of N-(benzo[1,2,3]triazol-1-yl)-N-(benzyl)acetamido)phenyl) carboxamides as severe acute respiratory syndrome coronavirus (SARS-CoV) 3CLpro inhibitors: identification of ML300 and noncovalent nanomolar inhibitors with an induced-fit binding.
Bioorg. Med. Chem. Lett.
PUBLISHED: 07-02-2013
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Herein we report the discovery and SAR of a novel series of SARS-CoV 3CLpro inhibitors identified through the NIH Molecular Libraries Probe Production Centers Network (MLPCN). In addition to ML188, ML300 represents the second probe declared for 3CLpro from this collaborative effort. The X-ray structure of SARS-CoV 3CLpro bound with a ML300 analog highlights a unique induced-fit reorganization of the S2-S4 binding pockets leading to the first sub-micromolar noncovalent 3CLpro inhibitors retaining a single amide bond.
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Biotransformation of a novel positive allosteric modulator of metabotropic glutamate receptor subtype 5 contributes to seizure-like adverse events in rats involving a receptor agonism-dependent mechanism.
Drug Metab. Dispos.
PUBLISHED: 07-02-2013
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Activation of metabotropic glutamate receptor subtype 5 (mGlu5) represents a novel strategy for therapeutic intervention into multiple central nervous system disorders, including schizophrenia. Recently, a number of positive allosteric modulators (PAMs) of mGlu5 were discovered to exhibit in vivo efficacy in rodent models of psychosis, including PAMs possessing varying degrees of agonist activity (ago-PAMs), as well as PAMs devoid of agonist activity. However, previous studies revealed that ago-PAMs can induce seizure activity and behavioral convulsions, whereas pure mGlu5 PAMs do not induce these adverse effects. We recently identified a potent and selective mGlu5 PAM, VU0403602, that was efficacious in reversing amphetamine-induced hyperlocomotion in rats. The compound also induced time-dependent seizure activity that was blocked by coadministration of the mGlu5 antagonist, 2-methyl-6-(phenylethynyl) pyridine. Consistent with potential adverse effects induced by ago-PAMs, we found that VU0403602 had significant allosteric agonist activity. Interestingly, inhibition of VU0403602 metabolism in vivo by a pan cytochrome P450 (P450) inactivator completely protected rats from induction of seizures. P450-mediated biotransformation of VU0403602 was discovered to produce another potent ago-PAM metabolite-ligand (M1) of mGlu5. Electrophysiological studies in rat hippocampal slices confirmed agonist activity of both M1 and VU0403602 and revealed that M1 can induce epileptiform activity in a manner consistent with its proconvulsant behavioral effects. Furthermore, unbound brain exposure of M1 was similar to that of the parent compound, VU0403602. These findings indicate that biotransformation of mGlu5 PAMs to active metabolite-ligands may contribute to the epileptogenesis observed after in vivo administration of this class of allosteric receptor modulators.
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Neuronal ablation of p-Akt at Ser473 leads to altered 5-HT1A/2A receptor function.
Neurochem. Int.
PUBLISHED: 06-21-2013
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The serotonergic system regulates a wide range of behavior, including mood and impulsivity, and its dysregulation has been associated with mood disorders, autism spectrum disorder, and addiction. Diabetes is a risk factor for these conditions. Insulin resistance in the brain is specifically associated with susceptibility to psychostimulant abuse. Here, we examined whether phosphorylation of Akt, a key regulator of the insulin signaling pathway, controls serotonin (5-HT) signaling. To explore how impairment in Akt function regulates 5-HT homeostasis, we used a brain-specific rictor knockout (KO) mouse model of impaired neuronal phosphorylation of Akt at Ser473. Cortical 5-HT1A and 5-HT2A receptor binding was significantly elevated in rictor KO mice. Concomitant with this elevated receptor expression, the 5-HT1A receptor agonist 8-Hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) led to an increased hypothermic response in rictor KO mice. The increased cortical 5-HT1A receptor density was associated with higher 5-HT1A receptor levels on the cortical cell surface. In contrast, rictor KO mice displayed significantly reduced head-twitch response (HTR) to the 5-HT2A/C agonist 2,5-dimethoxy-4-iodoamphetamine (DOI), with evidence of impaired 5-HT2A/C receptor signaling. In vitro, pharmacological inhibition of Akt significantly increased 5-HT1A receptor expression and attenuated DOI-induced 5-HT2A receptor signaling, thereby lending credence to the observed in vivo cross-talk between neuronal Akt signaling and 5-HT receptor regulation. These data reveal that defective central Akt function alters 5-HT signaling as well as 5-HT-associated behaviors, demonstrating a novel role for Akt in maintaining neuronal 5-HT receptor function.
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ML297 (VU0456810), the first potent and selective activator of the GIRK potassium channel, displays antiepileptic properties in mice.
ACS Chem Neurosci
PUBLISHED: 06-13-2013
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The G-protein activated, inward-rectifying potassium (K(+)) channels, "GIRKs", are a family of ion channels (Kir3.1-Kir3.4) that has been the focus of intense research interest for nearly two decades. GIRKs are comprised of various homo- and heterotetrameric combinations of four different subunits. These subunits are expressed in different combinations in a variety of regions throughout the central nervous system and in the periphery. The body of GIRK research implicates GIRK in processes as diverse as controlling heart rhythm, to effects on reward/addiction, to modulation of response to analgesics. Despite years of GIRK research, very few tools exist to selectively modulate GIRK channels activity and until now no tools existed that potently and selectively activated GIRKs. Here we report the development and characterization of the first truly potent, effective, and selective GIRK activator, ML297 (VU0456810). We further demonstrate that ML297 is active in two in vivo models of epilepsy, a disease where up to 40% of patients remain with symptoms refractory to present treatments. The development of ML297 represents a truly significant advancement in our ability to selectively probe GIRKs role in physiology as well as providing the first tool for beginning to understand GIRKs potential as a target for a diversity of therapeutic indications.
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Discovery of (R)-(2-fluoro-4-((-4-methoxyphenyl)ethynyl)phenyl) (3-hydroxypiperidin-1-yl)methanone (ML337), an mGlu3 selective and CNS penetrant negative allosteric modulator (NAM).
J. Med. Chem.
PUBLISHED: 06-13-2013
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A multidimensional, iterative parallel synthesis effort identified a series of highly selective mGlu3 NAMs with submicromolar potency and good CNS penetration. Of these, ML337 resulted (mGlu3 IC50 = 593 nM, mGlu2 IC50 >30 ?M) with B:P ratios of 0.92 (mouse) to 0.3 (rat). DMPK profiling and shallow SAR led to the incorporation of deuterium atoms to address a metabolic soft spot, which subsequently lowered both in vitro and in vivo clearance by >50%.
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Regulation of phospholipase D activity and phosphatidic acid production after purinergic (P2Y6) receptor stimulation.
J. Biol. Chem.
PUBLISHED: 05-30-2013
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Phosphatidic acid (PA) is a lipid second messenger located at the intersection of several lipid metabolism and cell signaling events including membrane trafficking, survival, and proliferation. Generation of signaling PA has long been primarily attributed to the activation of phospholipase D (PLD). PLD catalyzes the hydrolysis of phosphatidylcholine into PA. A variety of both receptor-tyrosine kinase and G-protein-coupled receptor stimulations have been shown to lead to PLD activation and PA generation. This study focuses on profiling the PA pool upon P2Y6 receptor signaling manipulation to determine the major PA producing enzymes. Here we show that PLD, although highly active, is not responsible for the majority of stable PA being produced upon UDP stimulation of the P2Y6 receptor and that PA levels are tightly regulated. By following PA flux in the cell we show that PLD is involved in an initial increase in PA upon receptor stimulation; however, when PLD is blocked, the cell compensates by increasing PA production from other sources. We further delineate the P2Y6 signaling pathway showing that phospholipase C?3 (PLC?3), PLC?1, DGK? and PLD are all downstream of receptor activation. We also show that DGK? is a novel negative regulator of PLD activity in this system that occurs through an inhibitory mechanism with PKC?. These results further define the downstream events resulting in PA production in the P2Y6 receptor signaling pathway.
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Substituted 1-Phenyl-3-(pyridin-2-yl)urea negative allosteric modulators of mGlu5: discovery of a new tool compound VU0463841 with activity in rat models of cocaine addiction.
ACS Chem Neurosci
PUBLISHED: 05-29-2013
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Cocaine is a powerful and highly addictive stimulant that disrupts the normal reward circuitry in the central nervous system (CNS), producing euphoric effects. Cocaine use can lead to acute and life threatening emergencies, and abuse is associated with increased risk for contracting infectious diseases. Though certain types of behavioral therapy have proven effective for treatment of cocaine addiction, relapse remains high, and there are currently no approved medications for the treatment of cocaine abuse. Evidence has continued to accumulate that indicates a critical role for the metabotropic glutamate receptor subtype 5 (mGlu5) in the modulation of neural circuitry associated with the addictive properties of cocaine. While the small molecule mGlu5 negative allosteric modulator (NAM) field is relatively advanced, investigation into the potential of small molecule mGlu5 NAMs for the treatment of cocaine addiction remains an area of high interest. Herein we describe the discovery and characterization of a potent and selective compound 29 (VU0463841) with good CNS exposure in rats. The utility of 29 (VU0463841) was demonstrated by its ability to attenuate drug seeking behaviors in relevant rat models of cocaine addiction.
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Octahydropyrrolo[3,4-c]pyrrole negative allosteric modulators of mGlu1.
Bioorg. Med. Chem. Lett.
PUBLISHED: 05-23-2013
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Development of SAR in an octahydropyrrolo[3,4-c]pyrrole series of negative allosteric modulators of mGlu1 using a functional cell-based assay is described in this Letter. The octahydropyrrolo[3,4-c]pyrrole scaffold was chosen as an isosteric replacement for the piperazine ring found in the initial hit compound. Characterization of selected compounds in protein binding assays was used to identify the most promising analogs, which were then profiled in P450 inhibition assays in order to further assess the potential for drug-likeness within this series of compounds.
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Inhibition of the TRPC5 ion channel protects the kidney filter.
J. Clin. Invest.
PUBLISHED: 05-21-2013
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An intact kidney filter is vital to retention of essential proteins in the blood and removal of waste from the body. Damage to the filtration barrier results in albumin loss in the urine, a hallmark of cardiovascular disease and kidney failure. Here we found that the ion channel TRPC5 mediates filtration barrier injury. Using Trpc5-KO mice, a small-molecule inhibitor of TRPC5, Ca2+ imaging in isolated kidney glomeruli, and live imagining of podocyte actin dynamics, we determined that loss of TRPC5 or its inhibition abrogates podocyte cytoskeletal remodeling. Inhibition or loss of TRPC5 prevented activation of the small GTP-binding protein Rac1 and stabilized synaptopodin. Importantly, genetic deletion or pharmacologic inhibition of TRPC5 protected mice from albuminuria. These data reveal that the Ca2+-permeable channel TRPC5 is an important determinant of albuminuria and identify TRPC5 inhibition as a therapeutic strategy for the prevention or treatment of proteinuric kidney disease.
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Discovery and SAR of a novel series of GIRK1/2 and GIRK1/4 activators.
Bioorg. Med. Chem. Lett.
PUBLISHED: 05-14-2013
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This Letter describes a novel series of GIRK activators identified through an HTS campaign. The HTS lead was a potent and efficacious dual GIRK1/2 and GIRK1/4 activator. Further chemical optimization through both iterative parallel synthesis and fragment library efforts identified dual GIRK1/2 and GIRK1/4 activators as well as the first examples of selective GIRK1/4 activators. Importantly, these compounds were inactive on GIRK2 and other non-GIRK1 containing GIRK channels, and SAR proved shallow.
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Discovery of molecular switches within a GIRK activator scaffold that afford selective GIRK inhibitors.
Bioorg. Med. Chem. Lett.
PUBLISHED: 05-13-2013
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This letter describes a multi-dimensional SAR campaign based on a potent, efficacious and selective GIRK1/2 activator (~10-fold versus GIRK1/4 and inactive on nonGIRK 1-containing GIRKs, GIRK 2 or GIRK2/3). Further chemical optimization through an iterative parallel synthesis effort identified multiple molecular switches that modulated the mode of pharmacology from activator to inhibitor, as well as engendering varying selectivity profiles for GIRK1/2 and GIRK1/4. Importantly, these compounds were all inactive on nonGIRK1 containing GIRK channels. However, SAR was challenging as subtle structural modifications had large effects on both mode of pharmacology and GIRK1/2 and GIRK1/4 channel selectivity.
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Dynamic subunit stoichiometry confers a progressive continuum of pharmacological sensitivity by KCNQ potassium channels.
Proc. Natl. Acad. Sci. U.S.A.
PUBLISHED: 05-06-2013
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Voltage-gated KCNQ1 (Kv7.1) potassium channels are expressed abundantly in heart but they are also found in multiple other tissues. Differential coassembly with single transmembrane KCNE beta subunits in different cell types gives rise to a variety of biophysical properties, hence endowing distinct physiological roles for KCNQ1-KCNEx complexes. Mutations in either KCNQ1 or KCNE1 genes result in diseases in brain, heart, and the respiratory system. In addition to complexities arising from existence of five KCNE subunits, KCNE1 to KCNE5, recent studies in heterologous systems suggest unorthodox stoichiometric dynamics in subunit assembly is dependent on KCNE expression levels. The resultant KCNQ1-KCNE channel complexes may have a range of zero to two or even up to four KCNE subunits coassembling per KCNQ1 tetramer. These findings underscore the need to assess the selectivity of small-molecule KCNQ1 modulators on these different assemblies. Here we report a unique small-molecule gating modulator, ML277, that potentiates both homomultimeric KCNQ1 channels and unsaturated heteromultimeric (KCNQ1)4(KCNE1)n (n < 4) channels. Progressive increase of KCNE1 or KCNE3 expression reduces efficacy of ML277 and eventually abolishes ML277-mediated augmentation. In cardiomyocytes, the slowly activating delayed rectifier potassium current, or IKs, is believed to be a heteromultimeric combination of KCNQ1 and KCNE1, but it is not entirely clear whether IKs is mediated by KCNE-saturated KCNQ1 channels or by channels with intermediate stoichiometries. We found ML277 effectively augments IKs current of cultured human cardiomyocytes and shortens action potential duration. These data indicate that unsaturated heteromultimeric (KCNQ1)4(KCNE1)n channels are present as components of IKs and are pharmacologically distinct from KCNE-saturated KCNQ1-KCNE1 channels.
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Spiroaminal Model Systems of the Marineosins with Final Step Pyrrole Incorporation.
Tetrahedron Lett.
PUBLISHED: 04-23-2013
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In this Letter, we describe a short, 6-step enantioselective route to spiroaminal lactam model systems reminiscent of marineosins A and B has been developed starting from either (R)- or (S)-hydroxysuccinic acid, respectively, in ~9% overall yield. This route enables late stage incorporation of the pyrrole ring at C5 via nucleophilic displacement of an iminium triflate salt.
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Allosteric modulation of the M1 muscarinic acetylcholine receptor: improving cognition and a potential treatment for schizophrenia and Alzheimers disease.
Drug Discov. Today
PUBLISHED: 04-16-2013
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Allosteric modulation of AMPA, NR2B, mGlu2, mGlu5 and M1, targeting glutamatergic dysfunction, represents a significant area of research for the treatment of schizophrenia. Of these targets, clinical promise has been demonstrated using muscarinic activators for the treatment of Alzheimers disease (AD) and schizophrenia. These diseases have inspired researchers to determine the effects of modulating cholinergic transmission in the forebrain, which is primarily regulated by one of five subtypes of muscarinic acetylcholine receptor (mAChR), a subfamily of G-protein-coupled receptors (GPCRs). Of these five subtypes, M1 is highly expressed in brain regions responsible for learning, cognition and memory. Xanomeline, an orthosteric muscarinic agonist with modest selectivity, was one of the first compounds that displayed improvements in behavioral disturbances in AD patients and efficacy in schizophrenics. Since these initial clinical results, many scientists, including those in our laboratories, have strived to elucidate the role of M1 with compounds that display improved selectivity for this receptor by targeting allosteric modes of receptor activation. A survey of selected compounds in this area will be presented.
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N-Acyl-N-arylpiperazines as negative allosteric modulators of mGlu1: identification of VU0469650, a potent and selective tool compound with CNS exposure in rats.
Bioorg. Med. Chem. Lett.
PUBLISHED: 04-02-2013
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Development of SAR in an N-acyl-N-arylpiperazine series of negative allosteric modulators of mGlu1 using a functional cell-based assay is described in this Letter. Characterization of selected compounds in protein binding assays was used to aid in selecting VU0469650 for further profiling in ancillary pharmacology assays and pharmacokinetic studies. VU0469650 demonstrated an excellent selectivity profile and good exposure in both plasma and brain samples following intraperitoneal dosing in rats.
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Synthesis and structure-activity relationships of a novel and selective bone morphogenetic protein receptor (BMP) inhibitor derived from the pyrazolo[1.5-a]pyrimidine scaffold of dorsomorphin: the discovery of ML347 as an ALK2 versus ALK3 selective MLPCN
Bioorg. Med. Chem. Lett.
PUBLISHED: 02-11-2013
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A structure-activity relationship of the 3- and 6-positions of the pyrazolo[1,5-a]pyrimidine scaffold of the known BMP inhibitors dorsomorphin, 1, LDN-193189, 2, and DMH1, 3, led to the identification of a potent and selective compound for ALK2 versus ALK3. The potency contributions of several 3-position substituents were evaluated with subtle structural changes leading to significant changes in potency. From these studies, a novel 5-quinoline molecule was identified and designated an MLPCN probe molecule, ML347, which shows >300-fold selectivity for ALK2 and presents the community with a selective molecular probe for further biological evaluation.
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Discovery of ML326: The first sub-micromolar, selective M5 PAM.
Bioorg. Med. Chem. Lett.
PUBLISHED: 01-21-2013
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This Letter describes the further chemical optimization of the M5 PAM MLPCN probes ML129 and ML172. A multi-dimensional iterative parallel synthesis effort quickly explored isatin replacements and a number of southern heterobiaryl variations with no improvement over ML129 and ML172. An HTS campaign identified several weak M5 PAMs (M5 EC50 >10?M) with a structurally related isatin core that possessed a southern phenethyl ether linkage. While SAR within the HTS series was very shallow and unable to be optimized, grafting the phenethyl ether linkage onto the ML129/ML172 cores led to the first sub-micromolar M5 PAM, ML326 (VU0467903), (human and rat M5 EC50s of 409nM and 500nM, respectively) with excellent mAChR selectivity (M1-M4 EC50s >30?M) and a robust 20-fold leftward shift of the ACh CRC.
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Synthesis of indole derived protease-activated receptor 4 antagonists and characterization in human platelets.
PLoS ONE
PUBLISHED: 01-01-2013
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Protease activated receptor-4 (PAR4) is one of the thrombin receptors on human platelets and is a potential target for the management of thrombotic disorders. We sought to develop potent, selective, and novel PAR4 antagonists to test the role of PAR4 in thrombosis and hemostasis. Development of an expedient three-step synthetic route to access a novel series of indole-based PAR4 antagonists also necessitated the development of a platelet based high-throughput screening assay. Screening and subsequent structure activity relationship analysis yielded several selective PAR4 antagonists as well as possible new scaffolds for future antagonist development.
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Enantioselective synthesis of C2-functionalized, N-protected morpholines and orthogonally N,N-protected piperazines via organocatalysis.
Tetrahedron Lett.
PUBLISHED: 12-29-2011
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In this Letter, we describe a novel three-step, one-pot procedure for the enantioselective synthesis of N-benzyl protected morpholines and orthogonally N,N-protected piperazines with chiral alkyl groups installed at the C2 position of each heterocyclic core via organocatalysis. This methodology allows for the rapid preparation of functionalized morpholines and piperazines that are not readily accessible through any other chemistry in good to excellent % ee (55-98% ee).
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Roles of the M1 muscarinic acetylcholine receptor subtype in the regulation of basal ganglia function and implications for the treatment of Parkinsons disease.
J. Pharmacol. Exp. Ther.
PUBLISHED: 12-01-2011
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Antagonists of the muscarinic acetylcholine receptors (mAChRs) were among the first treatments for Parkinsons disease. However, the clinical utility of mAChR antagonists is limited by adverse effects associated with the blockade of multiple mAChR subtypes. Understanding the roles of specific mAChR subtypes in regulating basal ganglia and motor function could lead to the development of novel agents that have antiparkinsonian activity with fewer adverse effects. Using the novel, highly selective M1 antagonist N-[3-oxo-3-[4-(4-pyridinyl)-1-piperazinyl]propyl]-2,1,3-benzothiadiazole-4-sulfonamide (VU0255035) and the M1 positive allosteric modulator benzylquinolone carboxylic acid, we investigated the roles of M1 receptors in cholinergic excitation and regulation of synaptic transmission in striatal medium spiny neurons (MSNs) and neurons in the subthalamic nucleus (STN) and substantia nigra pars reticulata (SNr). Electrophysiological studies demonstrate that M1 activation has excitatory effects on MSNs but plays little or no role in mAChR-mediated increases in firing frequency or the regulation of synaptic transmission in STN and SNr neurons. On the basis of this profile, M1-selective antagonists may have weak antiparkinsonian activity but would not have the full efficacy observed in nonselective mAChR antagonists. Consistent with this, the M1-selective antagonist VU0255035 partially reversed reserpine-induced akinesia and decreased haloperidol-induced catalepsy in rats but did not have the full efficacy observed with the nonselective mAChR antagonist scopolamine. These results suggest that the M1 receptor participates in the overall regulation of basal ganglia function and antiparkinsonian effects of mAChR antagonists but that other mAChR subtype(s) also play important roles at multiple levels of the basal ganglia motor circuit.
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Discovery, Synthesis, and Structure Activity Relationship of a Series of N-Aryl- bicyclo[2.2.1]heptane-2-carboxamides: Characterization of ML213 as a Novel KCNQ2 and KCNQ4 Potassium Channel Opener.
ACS Chem Neurosci
PUBLISHED: 11-30-2011
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Herein we report the discovery, synthesis and evaluation of a series of N-Aryl-bicyclo[2.2.1]heptane-2-carboxamides as selective KCNQ2 (K(v)7.2) and KCNQ4 (K(v)7.4) channel openers. The best compound, 1 (ML213) has an EC(50) of 230 nM (KCNQ2) and 510 nM (KCNQ4) and is selective for KCNQ2 and KCNQ4 channels versus a large battery of related potassium channels, as well as affording modest brain levels. This represents the first report of unique selectivity profile for KCNQ2 and KCNQ4 over the other channels (KCNQ1/3/5) and as such should prove to be a valuable tool compound for understanding these channels in regulating neuronal activity.
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The metabotropic glutamate receptor 4-positive allosteric modulator VU0364770 produces efficacy alone and in combination with L-DOPA or an adenosine 2A antagonist in preclinical rodent models of Parkinsons disease.
J. Pharmacol. Exp. Ther.
PUBLISHED: 11-16-2011
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Parkinsons disease (PD) is a debilitating neurodegenerative disorder associated with severe motor impairments caused by the loss of dopaminergic innervation of the striatum. Previous studies have demonstrated that positive allosteric modulators (PAMs) of metabotropic glutamate receptor 4 (mGlu?), including N-phenyl-7-(hydroxyimino) cyclopropa[b]chromen-1a-carboxamide, can produce antiparkinsonian-like effects in preclinical models of PD. However, these early mGlu? PAMsexhibited unsuitable physiochemical properties for systemic dosing, requiring intracerebroventricular administration and limiting their broader utility as in vivo tools to further understand the role of mGlu? in the modulation of basal ganglia function relevant to PD. In the present study, we describe the pharmacologic characterization of a systemically active mGlu? PAM, N-(3-chlorophenyl)picolinamide (VU0364770), in several rodent PD models. VU0364770 showed efficacy alone or when administered in combination with L-DOPA or an adenosine 2A (A2A) receptor antagonist currently in clinical development (preladenant). When administered alone, VU0364770 exhibited efficacy in reversing haloperidol-induced catalepsy, forelimb asymmetry-induced by unilateral 6-hydroxydopamine (6-OHDA) lesions of the median forebrain bundle, and attentional deficits induced by bilateral 6-OHDA nigrostriatal lesions in rats. In addition, VU0364770 enhanced the efficacy of preladenant to reverse haloperidol-induced catalepsy when given in combination. The effects of VU0364770 to reverse forelimb asymmetry were also potentiated when the compound was coadministered with an inactive dose of L-DOPA, suggesting that mGlu? PAMs may provide L-DOPA-sparing activity. The present findings provide exciting support for the potential role of selective mGlu? PAMs as a novel approach for the symptomatic treatment of PD and a possible augmentation strategy with either L-DOPA or A2A antagonists.
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