mGluR2 positive allosteric modulators: a patent review (2009 - present)

Current Market Potential and Prospects of Copper-based Pyridine Derivatives: A Review

Nicotine, minodronic acid, nicotinamide (niacin), zolpidem, zolimidine, and other pyridine-based chemicals play vital roles in medicine and biology. Pyridinecontaining drugs are widely available on the market to treat a wide range of human ailments. As a result of these advances, pyridine research is continually expanding, and there are now higher expectations for how it may aid in the treatment of numerous ailments. This evaluation incorporates data acquired from sources, like PubMed, to provide a thorough summary of the approved drugs and bioactivity data for compounds containing pyridine. Most of the reactions discussed in this article will provide readers with a deeper understanding of various pyridine-related examples, which is necessary for the creation of copper catalysis-based synthetic processes that are more accessible, secure, environmentally friendly, and practical, and that also have higher accuracy and selectivity. This paper also discusses significant innovations in the multi-component copper-catalyzed synthesis of N-heterocycles (pyridine), with the aim of developing precise, cost-effective, and environmentally friendly oxygenation and oxidation synthetic methods for the future synthesis of additional novel pyridine base analogs. Therefore, the review article will serve as a novel platform for researchers investigating copperbased pyridine compounds.

Scaffold Hopping to Imidazo[1,2-a]pyrazin-8-one Positive Allosteric Modulators of Metabotropic Glutamate 2 Receptor

Glutamate hyperfunction is implicated in multiple neurological and psychiatric diseases. Activation of the mGlu2 receptor results in reduced glutamate release and decreased excitability representing a promising novel therapeutic agent for the treatment of disorders such as epilepsy, schizophrenia, mood, anxiety, and other neuropsychiatric disorders. We have previously reported substantial efforts leading to potent and selective mGlu2 PAMs from different chemical series. Herein, the discovery and optimization of a novel series of imidazopyrazinone mGlu2 PAMs are reported. This new scaffold originated from computational searching of fragment databases and comparison with our previously explored scaffolds. Optimization guided by our robust understanding of SAR from former series led to potent, selective, and brain-penetrant compounds.

Novel rapid-acting glutamatergic modulators: Targeting the synaptic plasticity in depression

Major depressive disorder (MDD) is severely prevalent, and conventional monoaminergic antidepressants gradually exhibit low therapeutic efficiency, especially for patients with treatment-resistant depression. A neuroplasticity hypothesis is an emerging advancement in the mechanism of depression, mainly expressed in the glutamate system, e.g., glutamate receptors and signaling. Dysfunctional glutamatergic neurotransmission is currently considered to be closely associated with the pathophysiology of MDD. Biological function, pharmacological action, and signal attributes in the glutamate system both regulate the neural process. Specific functional subunits could be therapeutic targets to explore the novel glutamatergic modulators, which have fast-acting, and relatively sustained antidepressant effects. Here, the present review summarizes the pathophysiology of MDD found in the glutamate system, exploring the role of glutamate receptors and their downstream effects. These convergent mechanisms have prompted the development of other modulators targeting on glutamate system, including N-methyl-d-aspartate receptor antagonists, selective GluN2B-specific antagonists, glycine binding site agents, and regulators of metabotropic glutamate receptors. Relevant researches underly the putative mechanisms of these drugs, which reverse the damage of depression by regulating glutamatergic neurotransmission. It also provides further insight into the mechanism of depression and exploring potential targets for novel agent development.

Establishment of a rat model with ageing insomnia induced by D-galactosef and para-chlorophenylalanine

The current study aimed to establish a rat model of ageing insomnia induced by D-galactose and/or para-chlorophenylalanine. Following establishment of the model, body weights were measured, and Morris water maze and pentobarbital-induced sleep tests were performed. The serum levels of inflammatory mediators and the neural levels of neurotransmitters were detected. The results demonstrated that the body weights of PCPA+D-gal-induced ageing insomnia rats decreased significantly. Ageing insomnia rats exhibited longer latencies to the platform in the Morris water maze tests and fewer target crossings. The sleep latency of the model rats was longer and sleep time was shorter by contrast. The relative expression of hippocampal IL-6, TNF-α, NF-κB and mGluR2 mRNA of the PCPA+D-gal-induced ageing insomnia group was higher, while the relative expression of 5-HT_1AR and GABA_AR_a1 mRNA were lower. The serum levels of IL-1β, IL-6, TNF-α and brain level of glutamate increased in the PCPA+D-gal-induced ageing insomnia group, while the levels of 5-HT and GABA decreased. In conclusion, memory function, sleep time, expression of inflammatory factors and neurotransmitters are altered in ageing insomnia rats induced by D-galactose and para-chlorophenylalanine, indicating the successful establishment of a murine model of ageing insomnia.

Diaryl Ether: A Privileged Scaffold for Drug and Agrochemical Discovery

Diaryl ether (DE) is a functional scaffold existing widely both in natural products (NPs) and synthetic organic compounds. Statistically, DE is the second most popular and enduring scaffold within the numerous medicinal chemistry and agrochemical reports. Given its unique physicochemical properties and potential biological activities, DE nucleus is recognized as a fundamental element of medicinal and agrochemical agents aimed at different biological targets. Its drug-like derivatives have been extensively synthesized with interesting biological features including anticancer, anti-inflammatory, antiviral, antibacterial, antimalarial, herbicidal, fungicidal, insecticidal, and so on. In this review, we highlight the medicinal and agrochemical versatility of the DE motif according to the published information in the past decade and comprehensively give a summary of the target recognition, structure-activity relationship (SAR), and mechanism of action of its analogues. It is expected that this profile may provide valuable guidance for the discovery of new active ingredients both in drug and pesticide research.

Spiro-oxindole Piperidines and 3-(Azetidin-3-yl)-1H-benzimidazol-2-ones as mGlu2 Receptor PAMs

Starting from two weak mGlu₂ receptor positive allosteric modulator (PAM) HTS hits (4 and 5), a molecular hybridization strategy resulted in the identification of a novel spiro-oxindole piperidine series with improved activity and metabolic stability. Scaffold hopping around the spiro-oxindole core identified the 3-(azetidin-3-yl)-1H-benzimidazol-2-one as bioisoster. Medicinal chemistry optimization of these two novel chemotypes resulted in the identification of potent, selective, orally bioavailable, and brain penetrant mGluR₂ PAMs.

mGluR2 positive allosteric modulators: an updated patent review (2013-2018)

INTRODUCTION

Positive allosteric modulation of mGlu2 has attracted much interest as an alternative approach to classical orthosteric receptor activation. Two mGlu2 PAMS have advanced into the clinic. The results obtained in schizophrenia and MDD phase 2 clinical trials have tempered the high expectations put on selective mGlu2 receptor activation for treating these conditions; nevertheless, the search for novel therapeutic indications and novel chemotypes continues to be an active field of research.

AREAS COVERED

2013-2018 patent literature on mGlu2 receptor PAMs.

EXPERT OPINION

After a decade of intensive research, the mGlu2 PAM field has seen a deceleration in the last five years. Negative phase 2 schizophrenia clinical trials with JNJ-40411813 and AZD8529 seem to have tempered the high expectations of the scientific community on the utility of mGlu2 PAMs for the treatment of schizophrenia. Nevertheless, novel therapeutic indications continue to be explored and AZD8529 is currently in a phase 2 study for smoking cessation. The advances in medicinal chemistry and in pharmacology, with novel indications such as epilepsy, have set the stage in the field of mGlu2 receptor PAMs. Ongoing preclinical and clinical studies will contribute to define their optimal therapeutic indication and potential to become novel therapeutic agents.

Computational Drug Design Applied to the Study of Metabotropic Glutamate Receptors

Metabotropic glutamate (mGlu) receptors are a family of eight GPCRs that are attractive drug discovery targets to modulate glutamate action and response. Here we review the application of computational methods to the study of this family of receptors. X-ray structures of the extracellular and 7-transmembrane domains have played an important role to enable structure-based modeling approaches, whilst we also discuss the successful application of ligand-based methods. We summarize the literature and highlight the areas where modeling and experiment have delivered important understanding for mGlu receptor drug discovery. Finally, we offer suggestions of future areas of opportunity for computational work.

Discovery of Novel Central Nervous System Penetrant Metabotropic Glutamate Receptor Subtype 2 (mGlu2) Negative Allosteric Modulators (NAMs) Based on Functionalized Pyrazolo[1,5- a]pyrimidine-5-carboxamide and Thieno[3,2- b]pyridine-5-carboxamide Cores

A scaffold hopping exercise from a monocyclic mGlu₂ NAM with poor rodent PK led to two novel heterobicyclic series of mGlu₂ NAMs based on either a functionalized pyrazolo[1,5- a]pyrimidine-5-carboxamide core or a thieno[3,2- b]pyridine-5-carboxamide core. These novel analogues possess enhanced rodent PK, while also maintaining good mGlu₂ NAM potency, selectivity (versus mGlu₃ and the remaining six mGlu receptors), and high CNS penetration. Interestingly, SAR was divergent between the new 5,6-heterobicyclic systems.

Synthesis and Preliminary Studies of a Novel Negative Allosteric Modulator, 7-((2,5-Dioxopyrrolidin-1-yl)methyl)-4-(2-fluoro-4-[11C]methoxyphenyl) quinoline-2-carboxamide, for Imaging of Metabotropic Glutamate Receptor 2

Metabotropic glutamate 2 receptors (mGlu2) are involved in the pathogenesis of several CNS disorders and neurodegenerative diseases. Pharmacological modulation of this target represents a potential disease-modifying approach for the treatment of substance abuse, depression, schizophrenia, and dementias. While quantification of mGlu2 receptors in the living brain by positron emission tomography (PET) would help us better understand signaling pathways relevant to these conditions, few successful examples have been demonstrated to image mGlu2 in vivo, and a suitable PET tracer is yet to be identified. Herein we report the design and synthesis of a radiolabeled negative allosteric modulator (NAM) for mGlu2 PET tracer development based on a quinoline 2-carboxamide scaffold. The most promising candidate, 7-((2,5-dioxopyrrolidin-1-yl)methyl)-4-(2-fluoro-4-[11C]methoxyphenyl) quinoline-2-carboxamide ([11C]QCA) was prepared in 13% radiochemical yield (non-decay-corrected at the end of synthesis) with >99% radiochemical purity and >74 GBq/μmol (2 Ci/μmol) specific activity. While the tracer showed limited brain uptake (0.3 SUV), probably attributable to effects on PgP/Bcrp efflux pump, in vitro autoradiography studies demonstrated heterogeneous brain distribution and specific binding. Thus, [11C]QCA is a chemical probe that provides the basis for the development of a new generation mGlu2 PET tracers.

Design and Synthesis of mGlu2 NAMs with Improved Potency and CNS Penetration Based on a Truncated Picolinamide Core

Herein, we detail the optimization of the mGlu₂ negative allosteric modulator (NAM), VU6001192, by a reductionist approach to afford a novel, simplified mGlu₂ NAM scaffold. This new chemotype not only affords potent and selective mGlu₂ inhibition, as exemplified by VU6001966 (mGlu₂ IC₅₀ = 78 nM, mGlu₃ IC₅₀ > 30 μM), but also excellent central nervous system (CNS) penetration (K_p = 1.9, K_p,uu = 0.78), a feature devoid in all previously disclosed mGlu₂ NAMs (K_ps ≈ 0.3, K_p,uus ≈ 0.1). Moreover, this series, based on overall properties, represents an exciting lead series for potential mGlu₂ PET tracer development.

Reprint of Pharmacological and molecular characterization of the positive allosteric modulators of metabotropic glutamate receptor 2

The metabotropic glutamate receptor 2 (mGlu₂) plays an important role in the presynaptic control of glutamate release and several mGlu₂ positive allosteric modulators (PAMs) have been under assessment for their potential as antipsychotics. The binding mode of mGlu₂ PAMs is better characterized in functional terms while few data are available on the relationship between allosteric and orthosteric binding sites. Pharmacological studies characterizing binding and effects of two different chemical series of mGlu₂ PAMs are therefore carried out here using the radiolabeled mGlu₂ agonist ³[H]-LY354740 and mGlu₂ PAM ³[H]-2,2,2-TEMPS. A multidimensional approach to the PAM mechanism of action shows that mGlu₂ PAMs increase the affinity of ³[H]-LY354740 for the orthosteric site of mGlu2 as well as the number of ³[H]-LY354740 binding sites. ³[H]-2,2,2-TEMPS binding is also enhanced by the presence of LY354740. New residues in the allosteric rat mGlu2 binding pocket are identified to be crucial for the PAMs ligand binding, among these Tyr^3.40 and Asn^5.46. Also of remark, in the described experimental conditions S731A (Ser^5.42) residue is important only for the mGlu₂ PAM LY487379 and not for the compound PAM-1: an example of the structural differences among these mGlu₂ PAMs. This study provides a summary of the information generated in the past decade on mGlu₂ PAMs adding a detailed molecular investigation of PAM binding mode. Differences among mGlu₂ PAM compounds are discussed as well as the mGlu2 regions interacting with mGlu₂ PAM and NAM agents and residues driving mGlu2 PAM selectivity. This article is part of the Special Issue entitled 'Metabotropic Glutamate Receptors, 5 years on'.

Discovery of 8-Trifluoromethyl-3-cyclopropylmethyl-7-[(4-(2,4-difluorophenyl)-1-piperazinyl)methyl]-1,2,4-triazolo[4,3-a]pyridine (JNJ-46356479), a Selective and Orally Bioavailable mGlu2 Receptor Positive Allosteric Modulator (PAM)

Positive allosteric modulators of the metabotropic glutamate 2 receptor have generated great interest in the past decade. There is mounting evidence of their potential as therapeutic agents in the treatment of multiple central nervous system disorders. We have previously reported substantial efforts leading to potent and selective mGlu2 PAMs. However, finding compounds with the optimal combination of in vitro potency and good druglike properties has remained elusive, in part because of the hydrophobic nature of the allosteric binding site. Herein, we report on the lead optimization process to overcome the poor solubility inherent to the advanced lead 6. Initial prototypes already showed significant improvements in solubility while retaining good functional activity but displayed new liabilities associated with metabolism and hERG inhibition. Subsequent subtle modifications efficiently addressed those issues leading to the identification of compound 27 (JNJ-46356479). This new lead represents a more balanced profile that offers a significant improvement on the druglike attributes compared to previously reported leads.

Practical Strategies and Concepts in GPCR Allosteric Modulator Discovery: Recent Advances with Metabotropic Glutamate Receptors

Allosteric modulation of GPCRs has initiated a new era of basic and translational discovery, filled with therapeutic promise yet fraught with caveats. Allosteric ligands stabilize unique conformations of the GPCR that afford fundamentally new receptors, capable of novel pharmacology, unprecedented subtype selectivity, and unique signal bias. This review provides a comprehensive overview of the basics of GPCR allosteric pharmacology, medicinal chemistry, drug metabolism, and validated approaches to address each of the major challenges and caveats. Then, the review narrows focus to highlight recent advances in the discovery of allosteric ligands for metabotropic glutamate receptor subtypes 1-5 and 7 (mGlu1-5,7) highlighting key concepts ("molecular switches", signal bias, heterodimers) and practical solutions to enable the development of tool compounds and clinical candidates. The review closes with a section on late-breaking new advances with allosteric ligands for other GPCRs and emerging data for endogenous allosteric modulators.

Molecular mechanism of positive allosteric modulation of the metabotropic glutamate receptor 2 by JNJ-46281222

BACKGROUND AND PURPOSE

Allosteric modulation of the mGlu2 receptor is a potential strategy for treatment of various neurological and psychiatric disorders. Here, we describe the in vitro characterization of the mGlu2 positive allosteric modulator (PAM) JNJ-46281222 and its radiolabelled counterpart [(3) H]-JNJ-46281222. Using this novel tool, we also describe the allosteric effect of orthosteric glutamate binding and the presence of a bound G protein on PAM binding and use computational approaches to further investigate the binding mode.

EXPERIMENTAL APPROACH

We have used radioligand binding studies, functional assays, site-directed mutagenesis, homology modelling and molecular dynamics to study the binding of JNJ-46281222.

KEY RESULTS

JNJ-46281222 is an mGlu2 -selective, highly potent PAM with nanomolar affinity (KD = 1.7 nM). Binding of [(3) H]-JNJ-46281222 was increased by the presence of glutamate and greatly reduced by the presence of GTP, indicating the preference for a G protein bound state of the receptor for PAM binding. Its allosteric binding site was visualized and analysed by a computational docking and molecular dynamics study. The simulations revealed amino acid movements in regions expected to be important for activation. The binding mode was supported by [(3) H]-JNJ-46281222 binding experiments on mutant receptors.

CONCLUSION AND IMPLICATIONS

Our results obtained with JNJ-46281222 in unlabelled and tritiated form further contribute to our understanding of mGlu2 allosteric modulation. The computational simulations and mutagenesis provide a plausible binding mode with indications of how the ligand permits allosteric activation. This study is therefore of interest for mGlu2 and class C receptor drug discovery.

Role of calcium, glutamate and NMDA in major depression and therapeutic application

Major depression is a common, recurrent mental illness that affects millions of people worldwide. Recently, a unique fast neuroprotective and antidepressant treatment effect has been observed by ketamine, which acts via the glutamatergic system. Hence, a steady accumulation of evidence supporting a role for the excitatory amino acid neurotransmitter (EAA) glutamate in the treatment of depression has been observed in the last years. Emerging evidence indicates that N-methyl-D-aspartate (NMDA), group 1 metabotropic glutamate receptor antagonists and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) agonists have antidepressant properties. Indeed, treatment with NMDA receptor antagonists has shown the ability to sprout new synaptic connections and reverse stress-induced neuronal changes. Based on glutamatergic signaling, a number of therapeutic drugs might gain interest in the future. Several compounds such as ketamine, memantine, amantadine, tianeptine, pioglitazone, riluzole, lamotrigine, AZD6765, magnesium, zinc, guanosine, adenosine aniracetam, traxoprodil (CP-101,606), MK-0657, GLYX-13, NRX-1047, Ro25-6981, LY392098, LY341495, D-cycloserine, D-serine, dextromethorphan, sarcosine, scopolamine, pomaglumetad methionil, LY2140023, LY404039, MGS0039, MPEP, 1-aminocyclopropanecarboxylic acid, all of which target this system, have already been brought up, some of them recently. Drugs targeting the glutamatergic system might open up a promising new territory for the development of drugs to meet the needs of patients with major depression.

The Emerging Role of Metabotropic Glutamate Receptors in the Pathophysiology of Chronic Stress-Related Disorders

Chronic stress-related psychiatric conditions such as anxiety, depression, and alcohol abuse are an enormous public health concern. The etiology of these pathologies is complex, with psychosocial stressors being among the most frequently discussed risk factors. The brain glutamatergic neurotransmitter system has often been found involved in behaviors and pathophysiologies resulting from acute stress and fear. Despite this, relatively little is known about the role of glutamatergic system components in chronic psychosocial stress, neither in rodents nor in humans. Recently, drug discovery efforts at the metabotropic receptor subtypes of the glutamatergic system (mGlu1-8 receptors) led to the identification of pharmacological tools with emerging potential in psychiatric conditions. But again, the contribution of individual mGlu subtypes to the manifestation of physiological, molecular, and behavioral consequences of chronic psychosocial stress remains still largely unaddressed. The current review will describe animal models typically used to analyze acute and particularly chronic stress conditions, including models of psychosocial stress, and there we will discuss the emerging roles for mGlu receptor subtypes. Indeed, accumulating evidence indicates relevance and potential therapeutic usefulness of mGlu2/3 ligands and mGlu5 receptor antagonists in chronic stress-related disorders. In addition, a role for further mechanisms, e.g. mGlu7-selective compounds, is beginning to emerge. These mechanisms are important to be analyzed in chronic psychosocial stress paradigms, e.g. in the chronic subordinate colony housing (CSC) model. We summarize the early results and discuss necessary future investigations, especially for mGlu5 and mGlu7 receptor blockers, which might serve to suggest improved therapeutic strategies to treat stress-related disorders.

Selective Negative Allosteric Modulation Of Metabotropic Glutamate Receptors – A Structural Perspective of Ligands and Mutants

The metabotropic glutamate receptors have a wide range of modulatory functions in the central nervous system. They are among the most highly pursued drug targets, with relevance for several neurological diseases, and a number of allosteric modulators have entered clinical trials. However, so far this has not led to a marketed drug, largely because of the difficulties in achieving subtype-selective compounds with desired properties. Very recently the first crystal structures were published for the transmembrane domain of two metabotropic glutamate receptors in complex with negative allosteric modulators. In this analysis, we make the first comprehensive structural comparison of all metabotropic glutamate receptors, placing selective negative allosteric modulators and critical mutants into the detailed context of the receptor binding sites. A better understanding of how the different mGlu allosteric modulator binding modes relates to selective pharmacological actions will be very valuable for rational design of safer drugs.

Molecular determinants of positive allosteric modulation of the human metabotropic glutamate receptor 2

BACKGROUND AND PURPOSE

The activation of the metabotropic glutamate receptor 2 (mGlu2 ) reduces glutamatergic transmission in brain regions where excess excitatory signalling is implicated in disorders such as anxiety and schizophrenia. Positive allosteric modulators (PAMs) can provide a fine-tuned potentiation of these receptors' function and are being investigated as a novel therapeutic approach. An extensive set of mutant human mGlu2 receptors were used to investigate the molecular determinants that are important for positive allosteric modulation at this receptor.

EXPERIMENTAL APPROACH

Site-directed mutagenesis, binding and functional assays were employed to identify amino acids important for the activity of nine PAMs. The data from the radioligand binding and mutagenesis studies were used with computational docking to predict a binding mode at an mGlu2 receptor model based on the recent structure of the mGlu1 receptor.

KEY RESULTS

New amino acids in TM3 (R635, L639, F643), TM5 (L732) and TM6 (W773, F776) were identified for the first time as playing an important role in the activity of mGlu2 PAMs.

CONCLUSIONS AND IMPLICATIONS

This extensive study furthers our understanding of positive allosteric modulation of the mGlu2 receptor and can contribute to improved future design of mGlu2 PAMs.

Pharmacological and pharmacokinetic properties of JNJ-40411813, a positive allosteric modulator of the mGlu2 receptor

Compounds modulating metabotropic glutamate type 2 (mGlu2) receptor activity may have therapeutic benefits in treating psychiatric disorders like schizophrenia and anxiety. The pharmacological and pharmacokinetic properties of a novel mGlu2 receptor-positive allosteric modulator (PAM), 1-butyl-3-chloro-4-(4-phenyl-1-piperidinyl)-2(1H)-pyridinone (JNJ-40411813/ADX71149) are described here. JNJ-40411813 acts as a PAM at the cloned mGlu2 receptor: EC50 = 147 ± 42 nmol/L in a [(35)S]GTPγS binding assay with human metabotropic glutamate type 2 (hmGlu2) CHO cells and EC50 = 64 ± 29 nmol/L in a Ca(2+) mobilization assay with hmGlu2 G α16 cotransfected HEK293 cells. [(35)S]GTPγS autoradiography on rat brain slices confirmed PAM activity of JNJ-40411813 on native mGlu2 receptor. JNJ-40411813 displaced [(3)H]JNJ-40068782 and [(3)H]JNJ-46281222 (mGlu2 receptor PAMs), while it failed to displace [(3)H]LY341495 (a competitive mGlu2/3 receptor antagonist). In rats, JNJ-40411813 showed ex vivo mGlu2 receptor occupancy using [(3)H]JNJ-46281222 with ED50 of 16 mg/kg (p.o.). PK-PD modeling using the same radioligand resulted in an EC50 of 1032 ng/mL. While JNJ-40411813 demonstrated moderate affinity for human 5HT2A receptor in vitro (K b = 1.1 μmol/L), higher than expected 5HT2A occupancy was observed in vivo (in rats, ED50 = 17 mg/kg p.o.) due to a metabolite. JNJ-40411813 dose dependently suppressed REM sleep (LAD, 3 mg/kg p.o.), and promoted and consolidated deep sleep. In fed rats, JNJ-40411813 (10 mg/kg p.o.) was rapidly absorbed (C max 938 ng/mL at 0.5 h) with an absolute oral bioavailability of 31%. Collectively, our data show that JNJ-40411813 is an interesting candidate to explore the therapeutic potential of mGlu2 PAMs, in in vivo rodents experiments as well as in clinical studies.

N-Bridged 5,6-bicyclic pyridines: Recent applications in central nervous system disorders

The search for novel heterobicyclic compounds within the drug-like chemical space continues to be an area of interest in medicinal chemistry. Unsaturated N-bridgehead heterocycles are well represented in marketed drugs for a variety of therapeutic areas, and continue to play an important role in central nervous system (CNS) drug discovery programs. Examples of medicinal chemistry strategies that make use of N-bridged 5,6-bicyclic pyridines are discussed here in this Minireview, which covers the literature from 2010 up to 2014. B1-class imidazopyridines and B3-class pyrazolopyridines have proven to be at the forefront of molecular prototypes that are capable of interacting with disease relevant targets in neurodegeneration and neuropsychiatry.

Novel metabotropic glutamate receptor 2/3 antagonists and their therapeutic applications: a patent review (2005 - present)

INTRODUCTION

This review focuses on the medicinal chemistry efforts directed toward the identification of competitive and noncompetitive antagonists of glutamate at group II metabotropic glutamate receptors (mGluRII: mGlu2/3 and mGlu2). This class of compounds holds promise for the treatment of CNS disorders such as major depression, cognitive deficits and sleep-wake disorders, and several pharmaceutical companies are advancing mGluRII antagonists from discovery research into clinical development.

AREA COVERED

This review article covers for the first time the patent applications that were published on mGlu2/3 orthosteric and allosteric antagonists between January 2005 and September 2014, with support from the primary literature, posters and oral communications from international congresses. Patent applications published prior to 2005 for which compositions of matter were largely described in peer review articles are briefly discussed with main findings.

EXPERT OPINION

Recent advances in the prodrug approach of novel mGlu2/3 orthosteric antagonists combined with the design of novel mGlu2/3 and mGlu2 negative allosteric modulators provide new therapeutic opportunities for neurologic and psychiatric disorders.

QSAR design of triazolopyridine mGlu2 receptor positive allosteric modulators

Two QSAR approaches were applied to assist the design and to prioritise the synthesis of new active mGlu2 receptor positive allosteric modulators (PAMs). With the aim to explore a particular point of substitution the models successfully prioritised molecules originating from chemistry ideas and a large virtual library. The two methods, 3D topomer CoMFA and support vector machines with 2D ECFP6 fingerprints, delivered good correlation and success in this prospective application. Fourteen molecules with different substituent decoration were identified by the in silico models and synthesised. They were found to be highly active and their mGlu2 receptor PAM activity (pEC50) was predicted within 0.3 and 0.4log units of error with the two methods. The value of the molecules and the models for the future of the project is discussed.