The inward rectifier potassium (Kir) channel Kir7.1 (KCNJ13) has recently emerged as a key regulator of melanocortin signaling in the brain, electrolyte homeostasis in the eye, and uterine muscle contractility during pregnancy. The pharmacological tools available for exploring the physiology and therapeutic potential of Kir7.1 have been limited to relatively weak and non-selective small-molecule inhibitors. Here, we report the discovery in a fluorescence-based high-throughput screen of a novel Kir7.1 channel inhibitor, VU714. Site-directed mutagenesis of pore-lining amino acid residues identified Glutamate 149 and Alanine 150 as essential determinants of VU714 activity. Lead optimization with medicinal chemistry generated ML418, which exhibits sub-micromolar activity (IC50 = 310 nM) and superior selectivity over other Kir channels (at least 17-fold selective over Kir1.1, Kir2.1, Kir2.2, Kir2.3, Kir3.1/3.2, and Kir4.1) except for Kir6.2/SUR1 (equally potent). Evaluation in the EuroFins Lead Profiling panel of 64 GPCRs, ion-channels and transporters for off-target activity of ML418 revealed a relatively clean ancillary pharmacology. While ML418 exhibited low CLHEP in human microsomes which could be modulated with lipophilicity adjustments, it showed high CLHEP in rat microsomes regardless of lipophilicity. A subsequent in vivo PK study of ML418 by intraperitoneal (IP) administration (30 mg/kg dosage) revealed a suitable PK profile (Cmax = 0.20 µM and Tmax = 3 hours) and favorable CNS distribution (mouse brain:plasma Kp of 10.9 to support in vivo studies for in vivo studies. ML418, which represents the current state-of-the-art in Kir7.1 inhibitors, should be useful for exploring the physiology of Kir7.1 in vitro and in vivo.
KCNJ13; thallium flux; electrophysiology; comparative modeling; melanocortin signaling; myometrium
Insecticide resistance is a growing threat to mosquito control programs around the world, thus creating the need to discover novel target sites and target-specific compounds for insecticide development. Emerging evidence suggests that mosquito inward rectifier potassium (Kir) channels represent viable molecular targets for developing insecticides with new mechanisms of action. Here we describe the discovery and characterization of VU041, a submicromolar-affinity inhibitor of Anopheles (An.) gambiae and Aedes (Ae.) aegypti Kir1 channels that incapacitates adult female mosquitoes from representative insecticide-susceptible and -resistant strains of An. gambiae (G3 and Akron, respectively) and Ae. aegypti (Liverpool and Puerto Rico, respectively) following topical application. VU041 is selective for mosquito Kir channels over several mammalian orthologs, with the exception of Kir2.1, and is not lethal to honey bees. Medicinal chemistry was used to develop an analog, termed VU730, which retains activity toward mosquito Kir1 but is not active against Kir2.1 or other mammalian Kir channels. Thus, VU041 and VU730 are promising chemical scaffolds for developing new classes of insecticides to combat insecticide-resistant mosquitoes and the transmission of mosquito-borne diseases, such as Zika virus, without harmful effects on humans and beneficial insects.
The synthesis and SAR of 4-methoxy-3-(piperidin-4-yl) benzamides identified after a high-throughput screen of the MLPCN library is reported. SAR was explored around the 3-piperidine subtituent as well as the amide functionality of the reported compounds. Starting from the initial lead compounds, 1-7, iterative medicinal chemistry efforts led to the identification of ML352 (10m). ML352 represents a potent and selective inhibitor of CHT based on a drug-like scaffold.
MLPCN; ML352; Choline transporter; CHT; Structure-activity relationship
Previous studies have shown that 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 the positive allosteric modulators with therapeutic implications of anti-chronic pain. Here, we report an iterative parallel synthesis effort and a structure-activity relationship of a series of arylsulfonamides, which led to the discovery of the first positive allosteric modulator (PAM) of MrgX1, ML382.
MrgX1; ML382; chronic pain; positive allosteric modulator; MLPCN; molecular probes
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 Ki = 36 nM and shows no activity against the other dopamine
receptors tested (>20 μM against D1, D2S, D2L, D3, and D5). Further in vivo studies showed that ML398 reversed cocaine-induced
hyperlocomotion at 10 mg/kg.
Dopamine 4 receptor antagonist; ML398; addiction; MLPCN
Metabotropic glutamate receptor 4 (mGlu4) negatively modulates GABA and glutamate release in the ‘indirect pathway’ of the basal ganglia, and has thus been proposed as a potential target to treat motor symptoms in Parkinson's disease. Here, we present an extensive comparison of the behavioural effects produced by the mGlu4 positive allosteric modulator (PAM), VU0364770, and the mGlu4 orthosteric agonist, LSP1-2111, in rats with unilateral 6-OHDA lesions. The compounds' activity was initially assessed in a test of haloperidol-induced catalepsy in intact rats, and effective doses were then evaluated in the hemiparkinsonian animal model. Neither of the two compounds modified the development of dyskinetic behaviours elicited by chronic treatment with full doses of l-DOPA. When given together with l-DOPA to rats with already established dyskinesias, neither VU0364770 nor LSP1-2111 modified the abnormal involuntary movement scores. VU0364770 potentiated, however, the motor stimulant effect of a sub-threshold l-DOPA dose in certain behavioural tests, whereas LSP1-2111 lacked this ability. Taken together, these results indicate that a pharmacological stimulation of mGlu4 lacks intrinsic antidyskinetic activity, but may have DOPA-sparing activity in Parkinson's disease. For the latter indication, mGlu4 PAMs appear to provide a better option than orthosteric agonists.
Parkinson's disease; Glutamate; Dopamine; Movement disorders; Plasticity; Dyskinesias; Metabotropic receptor
This Letter describes a detailed SAR analysis of the mGluR4 positive allosteric modulator, PHCCC. We have now developed compounds with improved potency and efficacy; in addition, compounds are presented that show selectivity for mGluR4 versus the other mGluR subtypes.
metabotropic glutamate receptor 4; allosteric modulation; positive allosteric modulator; PHCCC; Parkinson's disease; structure-activity relationship; SAR
Small-molecule probes can illuminate biological processes and aid in the assessment of emerging therapeutic targets by perturbing biological systems in a manner distinct from other experimental approaches. Despite the tremendous promise of chemical tools for investigating biology and disease, small-molecule probes were unavailable for most targets and pathways as recently as a decade ago. In 2005, the U.S. National Institutes of Health launched the decade-long Molecular Libraries Program with the intent of innovating in and broadening access to small-molecule science. This Perspective describes how novel small-molecule probes identified through the program are enabling the exploration of biological pathways and therapeutic hypotheses not otherwise testable. These experiences illustrate how small-molecule probes can help bridge the chasm between biological research and the development of medicines, but also highlight the need to innovate the science of therapeutic discovery.
The cholinergic hypothesis of schizophrenia emerged over 50 years ago based on clinical observations with both anticholinergics and pan-muscarinic agonists. Not until the 1990s did the cholinergic hypothesis of schizophrenia receive renewed enthusiasm based on clinical data with xanomeline, a muscarinic acetylcholine receptor M1/M4-preferring orthosteric agonist. In a clinical trial with Alzheimer’s patients, xanomeline not only improved cognitive performance, but also reduced psychotic behaviors. This encouraging data spurred a second clinical trial in schizophrenic patients, wherein xanomeline significantly improved the positive, negative and cognitive symptom clusters. However, the question remained: Was the antipsychotic efficacy due to activation of M1, M4 or both M1/M4? Classical orthosteric ligands lacked the muscarinic receptor subtype selectivity required to address this key question. More recently, functional assays have allowed for the discovery of ligands that bind at allosteric sites, binding sites distinct from the orthosteric (acetylcholine) site, which are structurally less conserved and thereby afford high levels of receptor subtype selectivity. Recently, allosteric ligands, with unprecedented selectivity for either M1 or M4, have been discovered and have demonstrated comparable efficacy to xanomeline in preclinical antipsychotic and cognition models. These data suggest that selective allosteric activation of either M1 or M4 has antipsychotic potential through distinct, yet complimentary mechanisms.
A high-throughput screen utilizing a depolarization-triggered thallium influx through KCNQ1 channels was developed and used to screen the MLSMR collection of over 300,000 compounds. An iterative medicinal chemistry approach was initiated and from this effort, ML277 was identified as a potent activator of KCNQ1 channels (EC50 = 260 nM). ML277 was shown to be highly selective against other KCNQ channels (>100-fold selectivity versus KCNQ2 and KCNQ4) as well as against the distantly related hERG potassium channel.
KCNQ1 activator; MLPCN probe; Potassium channels; Voltage-gated ion channels; ML277
A potent and selective inhibitor of KCNQ2, (S)-5 (ML252, IC50 = 69 nM), was discovered after a high-throughput screen of the MLPCN library was performed. SAR studies revealed a small structural change (ethyl group to hydrogen) caused a functional shift from antagonist to agonist activity (37, EC50 = 170 nM), suggesting an interaction at a critical site for controlling gating of KCNQ2 channels.
KCNQ2; inhibitor; Kv7; ion channels; ML252; MLPCN probe; mode switch; CNS
Herein we describe the discovery and development of a novel class of M4 positive allosteric modulators, culminating in the discovery of ML293. ML293 exhibited modest potency at the human M4 receptor (EC50 = 1.3 µM) and excellent efficacy as noted by the 14.6-fold leftward shift of the agonist concentration-response curve. ML293 was also selective versus the other muscarinic subtypes and displayed excellent in vivo PK properties in rat with low IV clearance (11.6 mL/min/kg) and excellent brain exposure (PO PBL, 10 mg/kg at 1 h, [Brain] = 10.3 µM, B:P = 0.85).
Positive allosteric modulator; M4; ML293; CNS penetration; Muscarinic receptor 4
There is an increasing amount of literature data showing the positive effects on preclinical anti-Parkinsonian rodent models with selective positive allosteric modulators of metabotropic glutamate receptor 4 (mGlu4).1 However, most of the data generated utilize compounds that have not been optimized for drug-like 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 anti-Parkinsonian model.
metabotropic glutamate receptors; mGlu4; positive allosteric modulators; Parkinson’s disease; haloperidol-induced catalepsy; structure-activity relationship (SAR); oral efficacy; brain penetration
Herein we report the discovery, synthesis, and evaluation of a series of N-aryl-bicyclo[2.2.1]heptane-2-carboxamides as selective KCNQ2 (Kv7.2) and KCNQ4 (Kv7.4) channel openers. The best compound, 1 (ML213), has an EC50 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 profiles 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.
KCNQ2; KCNQ4; activator; Kv7; ion channels; ML218; MLPCN probe
Herein we report the discovery, synthesis and evaluation of a series of N-Aryl-bicyclo[2.2.1]heptane-2-carboxamides as selective KCNQ2 (Kv7.2) and KCNQ4 (Kv7.4) channel openers. The best compound, 1 (ML213) has an EC50 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.
This Review describes recent activity in the advancement of ligands for the metabotropic glutamate 4 receptor subtype and their potential utility as central nervous system (CNS) therapeutics. Until recently, there was a paucity of compounds with suitable selectivity and druglike properties to elucidate the value of this target. The search for selective entities has led several groups to the investigation of allosteric modulators as a path to optimization of potential ligands. Recent efforts, discussed here, have afforded a variety of derivatives with improvements in potency, solubility, and pharmacokinetic properties that garner support for continued investigation and optimization.
Metabotropic glutamate receptor 4; orthosteric ligand; allosteric modulator; Parkinson’s disease; anxiety; pain; cognitive disorders; psychiatric disorders; neurodegenerative disorders; Class C GPCR
Of the eight metabotropic glutamate (mGlu) receptor subtypes, only mGlu7 is expressed presynaptically at the Schaffer collateral (SC)-CA1 synapse in the hippocampus in adult animals. Coupled with the inhibitory effects of Group III mGlu receptor agonists on transmission at this synapse, mGlu7 is thought to be the predominant autoreceptor responsible for regulating glutamate release at SC terminals. However, the lack of mGlu7-selective pharmacological tools has hampered direct testing of this hypothesis. We used a novel, selective mGlu7-negative allosteric modulator (NAM), ADX71743, and a newly described Group III mGlu receptor agonist, LSP4-2022, to elucidate the role of mGlu7 in modulating transmission in hippocampal area CA1 in adult C57BL/6J male mice. Interestingly, although mGlu7 agonists inhibit SC-CA1 EPSPs, we found no evidence for activation of mGlu7 by stimulation of SC-CA1 afferents. However, LSP4-2022 also reduced evoked monosynaptic IPSCs in CA1 pyramidal cells and, in contrast to its effect on SC-CA1 EPSPs, ADX71743 reversed the ability of high-frequency stimulation of SC afferents to reduce IPSC amplitudes. Furthermore, blockade of mGlu7 prevented induction of LTP at the SC-CA1 synapse and activation of mGlu7 potentiated submaximal LTP. Together, these data suggest that mGlu7 serves as a heteroreceptor at inhibitory synapses in area CA1 and that the predominant effect of activation of mGlu7 by stimulation of glutamatergic afferents is disinhibition, rather than reduced excitatory transmission. Furthermore, this mGlu7-mediated disinhibition is required for induction of LTP at the SC-CA1 synapse, suggesting that mGlu7 could serve as a novel therapeutic target for treatment of cognitive disorders.
glutamate; hippocampus; LTP; mGlu; mGlu7; mGlur7
Using a functional high-throughput screening (HTS) and subsequent solution-phase parallel synthesis approach, we have discovered a novel series of positive allosteric modulators for mGlu4, a G-protein coupled receptor. This series is comprised of a homopiperazine central core. The solution-phase parallel synthesis and SAR of analogs derived from this series will be presented. This series of positive allosteric modulators of mGlu4 provide critical research tools to further probe the mGlu4-mediated effects in Parkinson’s disease.
Herein we report the discovery, synthesis and evaluation of a series of N-(4-acetamido)-phenylpicolinamides as positive allosteric modulators of mGlu4.a 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.
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 report a general synthesis of 1,3-diarylsubstituted indazoles utilizing a two-step Suzuki cross-coupling/deprotection/N-arylation sequence. This procedure proceeds in excellent overall yield starting from the 3-iodo-N-Boc indazole derivative allowing for rapid access to these compounds.
This paper describes a detailed structure−activity relationship (SAR) analysis of the metabotropic glutamate receptor 4 (mGluR4) positive allosteric modulator, (−)-N-phenyl-7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxamide (PHCCC). We have now developed compounds with improved potency and efficacy; in addition, compounds are presented that show selectivity for mGluR4 versus the other mGluR subtypes.
Metabotropic glutamate receptor 4; allosteric modulation; positive allosteric modulator; PHCCC; Parkinson’s disease; structure−activity relationship; SAR
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.
Allosteric modulator; metabotropic glutamate
receptor; electrophysiology; hippocampus
This Letter describes the synthesis and SAR of the novel positive allosteric modulator, VU0155041, a compound that has shown in vivo efficacy in rodent models of Parkinson's disease. The synthesis takes advantage of an iterative parallel synthesis approach to rapidly synthesize and evaluate a number of analogs of VU0155041.
mGluR4; metabotropic glutamate receptor 4; allosteric modulator; PAM; Parkinson's disease
We report the synthesis and evaluation of a series of heterobiaryl amides as positive allosteric modulators of mGluR4. Compounds 9b and 9c showed submicromolar potency at both human and rat mGluR4. In addition, both 9b and 9c were shown to be centrally penetrant in rats using nontoxic vehicles, a major advance for the mGluR4 field.