Herein, we report the structure–activity relationships within a series of mGlu7 PAMs based on a pyrazolo[1,5-a]pyrimidine core with excellent CNS penetration (Kps > 1 and Kp,uus > 1). Analogues in this series proved to display a range of Group III mGlu receptor selectivity, but VU6005649 emerged as the first dual mGlu7/8 PAM, filling a void in the Group III mGlu receptor PAM toolbox and demonstrating in vivo efficacy in a mouse contextual fear conditioning model.Keywords: cognition; metabotropic glutamate receptor 7 (mGlu7); Positive allosteric modulator (PAM); Rett syndrome; VU6005649;

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.Keywords: Allosteric modulator; electrophysiology; hippocampus; metabotropic glutamate receptor

Herein we report the discovery, synthesis, and evaluation of a series of N-(4-acetamido)-phenylpicolinamides as positive allosteric modulators of mGlu4. Compounds from the series show submicromolar potency at both human and rat mGlu4. In addition, pharmacokinetic studies utilizing subcutaneous dosing demonstrated good brain exposure in rats.

There is an increasing amount of literature data showing the positive effects on preclinical antiparkinsonian rodent models with selective positive allosteric modulators of metabotropic glutamate receptor 4 (mGlu4). However, most of the data generated utilize compounds that have not been optimized for druglike properties, and as a consequence, they exhibit poor pharmacokinetic properties and thus do not cross the blood–brain barrier. Herein, we report on a series of N-4-(2,5-dioxopyrrolidin-1-yl)phenylpicolinamides with improved PK properties with excellent potency and selectivity as well as improved brain exposure in rodents. Finally, ML182 was shown to be orally active in the haloperidol induced catalepsy model, a well-established antiparkinsonian model.

Herein we report the discovery and SAR of a novel antagonist of metabotropic glutamate receptor 4 (mGlu4). The antagonist was discovered via a molecular switch from a closely related mGlu4 positive allosteric modulator (PAM). This antagonist (VU0448383) displays an IC50 value of 8.2 ± 0.4 μM and inhibits an EC80 glutamate response by 63.1 ± 6.6%.

Herein we disclose the synthesis and SAR of a series of 4-(phenylsulfamoyl)phenylacetamide compounds as mGlu4 positive allosteric modulators (PAMs) that were identified via a functional HTS. An iterative parallel approach to these compounds culminated in the discovery of VU0364439 (11) which represents the most potent (19.8 nM) mGlu4 PAM reported to date.Herein we disclose the synthesis and SAR of a series of 4-(phenylsulfamoyl)phenylacetamide compounds as mGlu4 positive allosteric modulators (PAMs) that were identified via a functional HTS. An iterative parallel approach to these compounds culminated in the discovery of VU0364439 (11) which represents the most potent (19.8 nM) mGlu4 PAM reported to date.

•Detailed review of the biology of mGlu receptors•Summary of the pharmacological tools and therapeutic merits of mGlu receptors•Review of mGlu structural features and evidence for heteromeric conformationsThe metabotropic glutamate (mGlu) receptors are a group of Class C seven-transmembrane spanning/G protein-coupled receptors (7TMRs/GPCRs). These receptors are activated by glutamate, one of the standard amino acids and the major excitatory neurotransmitter. By activating G protein-dependent and non-G protein-dependent signaling pathways, mGlus modulate glutamatergic transmission both in the periphery and throughout the central nervous system. Since the discovery of the first mGlu receptor, and especially during the last decade, a great deal of progress has been made in understanding the signaling, structure, pharmacological manipulation and therapeutic indications of the 8 mGlu members.