Profiling the Impact of mGlu/Elfn1 Protein Interactions on the Pharmacology of mGlu Allosteric Modulators.

The group III metabotropic glutamate receptors (mGlu receptors) are predominantly expressed presynaptically throughout the central nervous system (CNS) where they regulate the release of glutamate and GABA. These receptors have recently been shown to be anchored by transsynaptic expression of the laminin proteins ELFN1 and ELFN2. In particular, the mGlu receptor is localized at presynaptic active zones from pyramidal cells to somatostatin-containing interneurons with postsynaptic ELFN1, and this interaction drives the rapidly facilitating nature of these synapses in the hippocampus and cortex.

Discovery of a Novel sp‑Rich M Positive Allosteric Modulators (PAMs) Chemotype via Scaffold Hopping.

The M receptor has long been investigated as a promising CNS drug target, yet further research is essential to fully elucidate compound's Pharmacodynamic (PD) as well as Toxicokinetic (TK) effects. In this context, the development of structurally diverse and high-profile M PAM tool compounds remains highly valuable, as existing advanced tools exhibit notable structural similarity. One approach that can be considered during scaffold hopping exercise and can improve drug-like properties is to introduce additional sp carbon atoms and increase Fsp values; the fraction of sp hybridized carbons.

Characterization of Novel and Known Activators of Cannabinoid Receptor Subtype 2 Reveals Mixed Pharmacology That Differentiates Mycophenolate Mofetil and GW-842,166X from MDA7.

CB and CB cannabinoid receptors are members of the GPCR superfamily that modulate the effects of endocannabinoids. CB is the most abundant CB receptor in the central nervous system, while CB is present both peripherally and in the brain. CB plays a role in inflammation, as well as neurodegenerative and psychiatric disorders.

Discovery of Pre-Clinical Candidate /: A Highly Selective, Orally Bioavailable, and Structurally Distinct Tricyclic M Muscarinic Acetylcholine Receptor Positive Allosteric Modulator (PAM) with Robust In Vivo Efficacy.

Herein, we report the structure-activity relationship to develop novel tricyclic M positive allosteric modulator scaffolds with improved pharmacological properties. This endeavor involved modifying a 5-amino-3,4-dimethylthieno[2,3-]pyridazine-6-carboxamide core via a "tie-back" strategy to discover a novel tricyclic 3,4-dimethylpyrimido[4',5':4,5]thieno[2,3-]pyridazine core. From this exercise, / was identified as a preclinical candidate, which displays low nanomolar potency against both human and rat M.

Discovery of Thieno[3,2-]pyridine-5-carboxamide and 2,3-Difluorobenzamide Negative Allosteric Modulators of Metabotropic Glutamate Receptor Subtype 5.

This Letter describes the discovery of novel mGlu NAMs and . Starting from previously reported picolinamide compounds, a structure-activity relationship study of various core isosteres was conducted, leading to the identification of thieno[3,2-]pyridine-5-carboxamide and 2,3-difluorobenzamide as competent core replacements. These compounds are highly potent as well as brain penetrant with an IVIVC agreement and improved oral bioavailability in rats.

Application of Deuterium in an M Positive Allosteric Modulator Back-Up Program: The Discovery of VU6045422.

Recently, we disclosed VU0467319, an M positive allosteric modulator (PAM) clinical candidate that had successfully completed a phase I single ascending dose clinical trial. Pharmacokinetic assessment revealed that, in humans upon increasing dose, a circulating, inactive metabolite constituted a major portion of the total drug-related area under the curve (AUC). One approach the team employed to reduce inactive metabolite formation in the back-up program was the kinetic isotope effect, replacing the metabolically labile C-H bonds with shorter, more stable C-D bonds.

Discovery of 4-(5-Membered)Heteroarylether-6-methylpicolinamide Negative Allosteric Modulators of Metabotropic Glutamate Receptor Subtype 5.

This Letter details our efforts to develop novel, non-acetylene-containing metabotropic glutamate receptor subtype 5 (mGlu) negative allosteric modulators (NAMs) with improved pharmacological properties. This endeavor involved replacing the ether-linked pyrimidine moiety, a metabolic liability, with various 5-membered heterocycles. From this exercise, we identified , a highly brain penetrant and selective mGlu NAM which displayed moderate potency against both human and rat mGlu.

Discovery of VU0467319: an M Positive Allosteric Modulator Candidate That Advanced into Clinical Trials.

Herein we detail the of VU0467319 (VU319), an M Positive Allosteric Modulator (PAM) clinical candidate that successfully completed a Phase I Single Ascending Dose (SAD) clinical trial. VU319 () is a moderately potent M PAM (M PAM EC = 492 nM ± 2.9 nM, 71.

The cannabinoid CB receptor positive allosteric modulator EC21a exhibits complicated pharmacology .

Schizophrenia is a complex disease involving the dysregulation of numerous brain circuits and patients exhibit positive symptoms (hallucinations, delusions), negative symptoms (anhedonia), and cognitive impairments. We have shown that the antipsychotic efficacy of positive allosteric modulators (PAMs) of both the M muscarinic receptor and metabotropic glutamate receptor 1 (mGlu) involve the retrograde activation of the presynaptic cannabinoid type-2 (CB) receptor, indicating that CB activation or potentiation could result in a novel therapeutic strategy for schizophrenia. We used two complementary assays, receptor-mediated phosphoinositide hydrolysis and GIRK channel activation, to characterize a CB PAM scaffold, represented by the compound EC21a, to explore its potential as a starting point to optimize therapeutics for schizophrenia.

Discovery of VU6016235: A Highly Selective, Orally Bioavailable, and Structurally Distinct Tricyclic M Muscarinic Acetylcholine Receptor Positive Allosteric Modulator (PAM).

Herein, we report structure-activity relationship (SAR) studies to develop novel tricyclic M PAM scaffolds with improved pharmacological properties. This endeavor involved a "tie-back" strategy to replace a 5-amino-2,4-dimethylthieno[2,3-]pyrimidine-6-carboxamide core, which led to the discovery of two novel tricyclic cores. While both tricyclic cores displayed low nanomolar potency against both human and rat M and were highly brain-penetrant, the 2,4-dimethylpyrido[4',3':4,5]thieno[2,3-]pyrimidine tricycle core provided lead compound, , with an overall superior pharmacological and drug metabolism and pharmacokinetics (DMPK) profile, as well as efficacy in a preclinical antipsychotic animal model.

Discovery of VU6007496: Challenges in the Development of an M Positive Allosteric Modulator Backup Candidate.

Herein we report progress toward a backup clinical candidate to the M positive allosteric modulator (PAM) VU319/ACP-319. Scaffold-hopping from the pyrrolo[2,3-]pyridine-based M PAM VU6007477 to isomeric pyrrolo[3,2-]pyridine and thieno[3,2-]pyridine congeners identified several backup contenders. Ultimately, VU6007496, a pyrrolo[3,2-]pyridine, advanced into late stage profiling, only to be plagued with unanticipated, species-specific metabolism and active/toxic metabolites which were identified in our phenotypic seizure liability screen, preventing further development.

Discovery of VU6008677: A Structurally Distinct Tricyclic M Positive Allosteric Modulator with Improved CYP450 Profile.

This Letter details our efforts to develop novel tricyclic muscarinic acetylcholine receptor subtype 4 (M) positive allosteric modulator (PAM) scaffolds with improved pharmacological properties. This endeavor involved a "tie-back" strategy to replace the 3-amino-5-chloro-4,6-dimethylthieno[2,3-]pyridine-2-carboxamide core, which led to the discovery of two novel tricyclic cores: an 8-chloro-9-methylpyrido[3',2':4,5]thieno[3,2-]pyrimidin-4-amine core and 8-chloro-7,9-dimethylpyrido[3',2':4,5]furo[3,2-]pyrimidin-4-amine core. Both tricyclic cores displayed low nanomolar potency against human M and greatly reduced cytochrome P450 inhibition when compared with parent compound .

Development of VU6036864: A Triazolopyridine-Based High-Quality Antagonist Tool Compound of the M Muscarinic Acetylcholine Receptor.

While the muscarinic acetylcholine receptor mAChR subtype 5 (M) has been studied over decades, recent findings suggest that more in-depth research is required to elucidate a thorough understanding of its physiological function related to neurological and psychiatric disorders. Our efforts to identify potent, selective, and pharmaceutically favorable next-generation M antagonist tool compounds have led to the discovery of a novel triazolopyridine-based series. In particular, () showed exquisite potency (human M IC = 20 nM), good subtype selectivity (>500 fold selectivity against human M), desirable brain exposure ( = 0.

Development of a Selective and High Affinity Radioligand, [H]VU6013720, for the M Muscarinic Receptor.

M muscarinic receptors are highly expressed in the striatum and cortex, brain regions that are involved in diseases such as Parkinson's disease, schizophrenia, and dystonia. Despite potential therapeutic advantages of specifically targeting the M receptor, it has been historically challenging to develop highly selective ligands, resulting in undesired off-target activity at other members of the muscarinic receptor family. Recently, we have reported first-in-class, potent, and selective M receptor antagonists.

Differential Activity of Orthosteric Agonists and Allosteric Modulators at Metabotropic Glutamate Receptor 7.

Metabotropic glutamate receptor 7 (mGlu) is a G protein coupled receptor that has demonstrated promise as a therapeutic target across a number of neurologic and psychiatric diseases. Compounds that modulate the activity of mGlu, such as positive and negative allosteric modulators, may represent new therapeutic strategies to modulate receptor activity. The endogenous neurotransmitter associated with the mGlu receptor family, glutamate, exhibits low efficacy and potency in activating mGlu, and surrogate agonists, such as the compound L-(+)-2-Amino-4-phosphonobutyric acid (L-AP4), are often used for receptor activation and compound profiling.

Persistent challenges in the development of an mGlu PAM in vivo tool compound: The discovery of VU6046980.

Herein, we report on the further chemical optimization of the first reported mGlu positive allosteric modulator (PAM), VU6027459. Replacement of the quinoline core by a cinnoline scaffold increased mGlu PAM potency by ∼ 10-fold, and concomitant introduction of a chiral tricyclic motif led to potent mGlu PAMs with enantioselective mGlu receptor selectivity profiles. Of these, VU6046980 emerged as a putative in vivo tool compound with excellent CNS penetration (K = 4.

Discovery of a potent M antagonist with improved clearance profile. Part 2: Pyrrolidine amide-based antagonists.

This Letter describes our ongoing effort to improve the clearance of selective M antagonists. Herein, we report the replacement of the previously disclosed piperidine amide (4, disclosed in Part 1) with a pyrrolidine amide core. Several compounds within this series provided good potency, subtype selectivity, and low to moderate clearance profiles.

Discovery of a potent M antagonist with improved clearance profile. Part 1: Piperidine amide-based antagonists.

The lack of potent and selective tool compounds with pharmaceutically favorable properties limits the in vivo understanding of muscarinic acetylcholine receptor subtype 5 (M) biology. Previously, we presented a highly potent and selective M antagonist VU6019650 with a suboptimal clearance profile as our second-generation tool compound. Herein, we disclose our ongoing efforts to generate next-generation M antagonists with improved clearance profiles.

Development and profiling of mGlu NAMs with a range of saturable inhibition of agonist responses in vitro.

We describe here a series of metabotropic glutamate receptor 7 (mGlu) negative allosteric modulators (NAMs) with a saturable range of activity in inhibiting responses to an orthosteric agonist in two distinct in vitro pharmacological assays. The range of inhibition among compounds in this scaffold provides highly structurally related ligands with differential degrees of receptor blockade that can be used to understand inhibitory efficacy profiles in native tissue or in vivo.

Development of : A Potent, Highly Selective, and Systemically Active Orthosteric Antagonist of the M Muscarinic Acetylcholine Receptor for the Treatment of Opioid Use Disorder.

The muscarinic acetylcholine receptor (mAChR) subtype 5 (M) represents a novel potential target for the treatment of multiple addictive disorders, including opioid use disorder. Through chemical optimization of several functional high-throughput screening hits, () was identified as a novel M orthosteric antagonist with high potency (human M IC = 36 nM), M subtype selectivity (>100-fold selectivity against human M) and favorable physicochemical properties for systemic dosing in preclinical addiction models. In acute brain slice electrophysiology studies, blocked the nonselective muscarinic agonist oxotremorine-M-induced increases in neuronal firing rates of midbrain dopamine neurons in the ventral tegmental area, a part of the mesolimbic dopaminergic reward circuitry.

Synthesis and characterization of chiral 6-azaspiro[2.5]octanes as potent and selective antagonists of the M muscarinic acetylcholine receptor.

In this manuscript, we report a series of chiral 6-azaspiro[2.5]octanes and related spirocycles as highly potent and selective antagonists of the muscarinic acetylcholine receptor subtype 4 (mAChR). Chiral separation and subsequent X-ray crystallographic analysis of early generation analogs revealed the R enantiomer to possess excellent human and rat M potency, and further structure-activity relationship (SAR) studies on this chiral scaffold led to the discovery of VU6015241 (compound 19).

Discovery of structurally distinct tricyclic M positive allosteric modulator (PAM) chemotypes - Part 2.

This Letter details our efforts to develop novel tricyclic M PAM scaffolds with improved pharmacological properties. This endeavor involved a "tie-back" strategy to replace the 3-amino-4,6-dimethylthieno[2,3-b]pyridine-2-carboxamide core which lead to the discovery of two novel tricyclic cores: a 7,9-dimethylpyrido[3',2':4,5]thieno[3,2-d]pyrimidine core and 2,4-dimethylthieno[2,3-b:5,4-c']dipyridine core. Both tricyclic cores displayed low nanomolar potency against the human M receptor.

Positive allosteric modulators (PAMs) of the group II metabotropic glutamate receptors: Design, synthesis, and evaluation as ex-vivo tool compounds.

This letter describes synthesis and evaluation of two series of dual mGlu/mGlu positive allosteric modulators with moderate mGlu potency and robust mGlu potency in thallium flux assays. These compounds were profiled their ability to modulate mGlu-mediated signaling in central neurons by co-application of a selective mGlu NAM to isolate mGlu-selective effects. Using acute mouse brain slices from the prefrontal cortex, potentiation of group II mGlu receptor agonist Ca signaling in PFC pyramidal cells with either the dual mGlu/mGlu PAM 16e or 23d demonstrated effects mediated selectively via mGlu.

Discovery of the First Selective M Muscarinic Acetylcholine Receptor Antagonists with Antiparkinsonian and Antidystonic Efficacy.

Nonselective antagonists of muscarinic acetylcholine receptors (mAChRs) that broadly inhibit all five mAChR subtypes provide an efficacious treatment for some movement disorders, including Parkinson's disease and dystonia. Despite their efficacy in these and other central nervous system disorders, antimuscarinic therapy has limited utility due to severe adverse effects that often limit their tolerability by patients. Recent advances in understanding the roles that each mAChR subtype plays in disease pathology suggest that highly selective ligands for individual subtypes may underlie the antiparkinsonian and antidystonic efficacy observed with the use of nonselective antimuscarinic therapeutics.

Discovery of VU6028418: A Highly Selective and Orally Bioavailable M Muscarinic Acetylcholine Receptor Antagonist.

Herein, we report the SAR leading to the discovery of VU6028418, a potent M mAChR antagonist with high subtype-selectivity and attractive DMPK properties and across multiple species. VU6028418 was subsequently evaluated as a preclinical candidate for the treatment of dystonia and other movement disorders. During the characterization of VU6028418, a novel use of deuterium incorporation as a means to modulate CYP inhibition was also discovered.