GluN2A containing N-methyl-D-aspartate receptors are involved in neuropsychiatric disorders. Studies with GluN2A knockout mice revealed an anxiolytic and antidepressant-like phenotype across multiple behavioral tests and in humans. Despite its relevance, the development of selective GluN2A antagonists has been hindered by challenges in achieving compound specificity and favorable pharmacological profiles. While competitive antagonists show GluN2A preference, negative allosteric modulators like TCN-201 offer superior selectivity but suffer from poor solubility and glycine sensitivity. Subsequent analogues such as MPX-007 showed significant improvements in potency but remained unsuitable for in vivo use due to their efflux liability, associated with the presence of a sulfonamide moiety as an important pharmacophoric feature. Herein, we report a structurally distinct novel class of GluN2A-selective negative allosteric modulators identified through virtual screening of the MPX-007 binding site and advanced in vitro profile, with an optimized compound 6m, representing a promising and structurally unique tool for advancing mechanistic studies and exploring therapeutic potential targeting GluN2A.

A mainstay of the analgesic pharmacopeia for nearly seven decades and alone in its class, acetaminophen relieves mild-to-moderate pain and fever, without similar adverse gastrointestinal and cardiovascular effects associated with non-steroidal anti-inflammatory drugs. While safe and effective when used as directed, acetaminophen overdose may produce liver injury. This report describes discovery and pharmacological characterization of JNJ-10450232/NTM-006, an acetaminophen structural analog designed to retain the efficacy and overall safety profile of acetaminophen without risk of hepatotoxicity following overdose. In the carrageenan and complete Freund's adjuvant models of inflammatory pain and yeast model of fever in rats, JNJ-10450232/NTM-006 exhibited statistically significant effects comparable to acetaminophen in both maximal efficacy and potency. In rat pharmacokinetic studies, JNJ-10450232/NTM-006 exhibited a comparable maximal plasma concentration but higher volume of distribution and longer half-life than acetaminophen, potentially conferring an extended duration of action. In a mouse model of liver injury, acetaminophen produced elevations in aspartate and alanine transaminase activities and signs of hepatic necrosis, whereas JNJ-10450232/NTM-006 did not. Finally, following systemic administration, JNJ-10450232/NTM-006 and acetaminophen produced comparable peripheral levels of para-aminophenol and brain levels of pharmacologically active metabolite N-arachidonoyl-phenolamine (AM404), consistent with the hypothesis that both parent molecules are prodrugs and share the same central mechanism of analgesic action. Taken together, these results suggest JNJ-10450232/NTM-006 as a potentially clinically useful analgesic/antipyretic with improved benefit-to-risk ratio compared with current standards of care.

BACKGROUND AND PURPOSE:Non-selective NMDA receptor antagonism produces rapid symptom improvement in treatment-resistant depression; however, associated side effects necessitate medical oversight during administration. We hypothesised that selective GluN2A antagonism could provide similar efficacy with an improved side effect profile. Here, we report the pharmacology of JNJ-78911118, a brain-penetrant, GluN2A selective antagonist. EXPERIMENTAL APPROACH:JNJ-78911118 pharmacology and mechanism of action was characterised in vitro using fluorescence, voltage clamp and radioligand binding assays. Target engagement was measured using ex vivo receptor autoradiography, and effects on rat prefrontal cortex monoamine levels were measured using microdialysis. Synaptogenesis assays and patch clamp studies were used to demonstrate effects on synaptic plasticity. Cardiovascular safety and neurotoxicity were assessed in rats. KEY RESULTS:JNJ-78911118 blocked GluN1/2A receptors with an IC50 of 44 nM and showed selectivity against GluN1/2B, 2C and 2D receptors. Systemic administration produced concentration-dependent receptor occupancy, increased prefrontal cortex monoamine levels in wild type, but not in GluN2A knockout mice, and blocked theta burst induced LTP in the hippocampus. In addition, it produced increases in dendritic complexity and synapse number in vitro, and increased mEPSC frequency in rat cortical neurons in vivo. In rat toxicological studies, no Olney's lesions were observed, but acute increases in heart rate and blood pressure were detected. CONCLUSIONS AND IMPLICATIONS:JNJ-78911118 is a potent and selective GluN2A antagonist that reproduces the effect of known rapidly acting antidepressants (RAADs) on neurotransmitter levels and synaptic plasticity. This molecule is a powerful in vivo tool that will enhance understanding of GluN2A biology.

N-Methyl-d-aspartate receptors are ionotropic glutamate receptors that mediate fast excitatory neurotransmission in the central nervous system. These receptors play essential roles in synaptic plasticity, learning, and memory and are implicated in various neuropathological and psychiatric disorders. Selective modulation of NMDAR subtypes, particularly GluN2A, has proven challenging. The TCN-201 derivatives MPX-004 and MPX-007 are potent and selective for GluN2A receptors, yet their physical properties limit their in vivo utility. In this study, we optimized the MPX-004/MPX-007 scaffold by modifying the linker region between the distal halogenated aromatic ring and the central pyrazine nucleus, resulting in the identification of potent and selective compounds with improved drug-like properties. Notably, compound 1 was used to develop the first GluN2A NAM-based radioligand, and compound 11 showed improved pharmacokinetics and dose-dependent receptor occupancy in vivo. Thus, we provide an array of powerful new tools for the study of GluN2A receptors.

The discovery of the chemical synapse was a seminal finding in Neurobiology but the large body of microscopic interactions involved in synaptic transmission could hardly have been foreseen at the time of these first discoveries. Characterization of the molecular players at work at synapses and the increased granularity at which we can now analyze electrical and chemical signal processing that occur in even the simplest neuronal system are shining a new light on receptor interactions. The aim of this review is to discuss the complexity of some representative interactions between excitatory and inhibitory ligand-gated ion channels and/or G protein coupled receptors, as well as other key machinery that can impact neurotransmission and to explain how such mechanisms can be an important determinant of nervous system function.

A fundamental mechanism that drives the propagation of electrical signals in the nervous system is the activation of voltage-gated sodium channels. The sodium channel subtype Nav1.7 is critical for the transmission of pain-related signaling, with gain-of-function mutations in Nav1.7 resulting in various painful pathologies. Loss-of-function mutations cause complete insensitivity to pain and anosmia in humans that otherwise have normal nervous system function, rendering Nav1.7 an attractive target for the treatment of pain. Despite this, no Nav1.7 selective therapeutic has been approved for use as an analgesic to date. Here we present a summary of research that has focused on engineering peptides found in spider venoms to produce Nav1.7 selective antagonists. We discuss the progress that has been made on various scaffolds from different venom families and highlight the challenges that remain in the effort to produce a Nav1.7 selective, venom-based analgesic.

IntroductionBlockade of GluN2B (NR2B)‐containing NMDA receptors has been proposed as a therapy for a number of neurological and psychiatric diseases including mood disorders. A number of GluN2B antagonists have been identified and developed over the last three decades. These compounds, however, have significant limitations in regard to their selectivity or drug‐like properties (e.g. oral bioavailability).MethodsThe pharmacology of JNJ‐63612445 was explored using in‐vitro assays (calcium mobilization, competitive radioligand binding, electrophysiology), ex‐vivo slice autoradiography and in‐vivo electrophysiology (synaptic transmission and plasticity) and behavior.ResultsJNJ‐63612445 is a high affinity (pKi=8.0), potent (pIC50=7.8) and selective negative allosteric modulator of GluN2B receptors. Upon oral dosing, the compound occupied GluN2B receptors in rat hippocampus in time‐ and concentration‐dependent manner, reaching 50% occupancy at the plasma concentration of 443 ng/ml. JNJ‐63612445 at 1 μM blocked 54% of NMDA receptor‐mediated EPSC in rat neonatal slices similar to other GluN2B antagonists. The compounds at the dose 10 mg/kg s.c. inhibited in vivo long‐term depression measured in the CA1 of anesthetized rats without effects on the basal synaptic transmission. Given orally at the dose 30 mg/kg in mice, the compound significantly reduces immobility time in a tail‐suspension test, while occupying approximately 89% of the GluN2B receptors in the hippocampus.ConclusionsJNJ‐63612445 represents an example of new generation of potent, selective, and orally available GluN2B antagonists.Support or Funding InformationFunding informationAuthors are full time employees of Janssen Research & Development, LLC. The research was funded by the company.

Pain is a significant public health burden in the United States, and current treatment approaches rely heavily on opioids, which often have limited efficacy and can lead to addiction. In humans, functional loss of the voltage-gated sodium channel Nav1.7 leads to pain insensitivity without deficits in the central nervous system. Accordingly, discovery of a selective Nav1.7 antagonist should provide an analgesic without abuse liability and an improved side-effect profile. Huwentoxin-IV, a component of tarantula venom, potently blocks sodium channels and is an attractive scaffold for engineering a Nav1.7-selective molecule. To define the functional impact of alterations in huwentoxin-IV sequence, we produced a library of 373 point mutants and tested them for Nav1.7 and Nav1.2 activity. We then combined favorable individual changes to produce combinatorial mutants that showed further improvements in Nav1.7 potency (E1N, E4D, Y33W, Q34S–Nav1.7 pIC50 = 8.1 ± 0.08) and increased selectivity over other Nav isoforms (E1N, R26K, Q34S, G36I, Nav1.7 pIC50 = 7.2 ± 0.1, Nav1.2 pIC50 = 6.1 ± 0.18, Nav1.3 pIC50 = 6.4 ± 1.0), Nav1.4 is inactive at 3 μm, and Nav1.5 is inactive at 10 μm. We also substituted noncoded amino acids at select positions in huwentoxin-IV. Based on these results, we identify key determinants of huwentoxin's Nav1.7 inhibition and propose a model for huwentoxin-IV's interaction with Nav1.7. These findings uncover fundamental features of huwentoxin involved in Nav1.7 blockade, provide a foundation for additional optimization of this molecule, and offer a basis for the development of a safe and effective analgesic.

Pain places a devastating burden on patients and society and current pain therapeutics exhibit limitations in efficacy, unwanted side effects and the potential for drug abuse and diversion. Although genetic evidence has clearly demonstrated that the voltage-gated sodium channel, Nav1.7, is critical to pain sensation in mammals, pharmacological inhibitors of Nav1.7 have not yet fully recapitulated the dramatic analgesia observed in Nav1.7-null subjects. Using the tarantula venom-peptide ProTX-II as a scaffold, we engineered a library of over 1500 venom-derived peptides and identified JNJ63955918 as a potent, highly selective, closed-state Nav1.7 blocking peptide. Here we show that JNJ63955918 induces a pharmacological insensitivity to pain that closely recapitulates key features of the Nav1.7-null phenotype seen in mice and humans. Our findings demonstrate that a high degree of selectivity, coupled with a closed-state dependent mechanism of action is required for strong efficacy and indicate that peptides such as JNJ63955918 and other suitably optimized Nav1.7 inhibitors may represent viable non-opioid alternatives for the pharmacological treatment of severe pain.

In the central nervous system, the ATP-gated Purinergic receptor P2X ligand-gated ion channel 7 (P2X7) is expressed in glial cells and modulates neurophysiology via release of gliotransmitters, including the proinflammatory cytokine interleukin (IL)-1β. In this study, we characterized JNJ-42253432 [2-methyl-N-([1-(4-phenylpiperazin-1-yl)cyclohexyl]methyl)-1,2,3,4-tetrahydroisoquinoline-5-carboxamide] as a centrally permeable (brain-to-plasma ratio of 1), high-affinity P2X7 antagonist with desirable pharmacokinetic and pharmacodynamic properties for in vivo testing in rodents. JNJ-42253432 is a high-affinity antagonist for the rat (pKi 9.1 ± 0.07) and human (pKi 7.9 ± 0.08) P2X7 channel. The compound blocked the ATP-induced current and Bz-ATP [2′(3′)-O-(4-benzoylbenzoyl)adenosine-5′-triphosphate tri(triethylammonium)]–induced release of IL-1β in a concentration-dependent manner. When dosed in rats, JNJ-42253432 occupied the brain P2X7 channel with an ED50 of 0.3 mg/kg, corresponding to a mean plasma concentration of 42 ng/ml. The compound blocked the release of IL-1β induced by Bz-ATP in freely moving rat brain. At higher doses/exposure, JNJ-42253432 also increased serotonin levels in the rat brain, which is due to antagonism of the serotonin transporter (SERT) resulting in an ED50 of 10 mg/kg for SERT occupancy. JNJ-42253432 reduced electroencephalography spectral power in the α-1 band in a dose-dependent manner; the compound also attenuated amphetamine-induced hyperactivity. JNJ-42253432 significantly increased both overall social interaction and social preference, an effect that was independent of stress induced by foot-shock. Surprisingly, there was no effect of the compound on either neuropathic pain or inflammatory pain behaviors. In summary, in this study, we characterize JNJ-42253432 as a novel brain-penetrant P2X7 antagonist with high affinity and selectivity for the P2X7 channel.

Voltage-gated sodium channels (VGSCs) are essential to the normal function of the vertebrate nervous system. Aberrant function of VGSCs underlies a variety of disorders, including epilepsy, arrhythmia, and pain. A large number of animal toxins target these ion channels and may have significant therapeutic potential. Most of these toxins, however, have not been characterized in detail. Here, by combining patch clamp electrophysiology and radioligand binding studies with peptide mutagenesis, NMR structure determination, and molecular modeling, we have revealed key molecular determinants of the interaction between the tarantula toxin huwentoxin-IV and two VGSC isoforms, Nav1.7 and Nav1.2. Nine huwentoxin-IV residues (F6A, P11A, D14A, L22A, S25A, W30A, K32A, Y33A, and I35A) were important for block of Nav1.7 and Nav1.2. Importantly, molecular dynamics simulations and NMR studies indicated that folding was normal for several key mutants, suggesting that these amino acids probably make specific interactions with sodium channel residues. Additionally, we identified several amino acids (F6A, K18A, R26A, and K27A) that are involved in isoform-specific VGSC interactions. Our structural and functional data were used to model the docking of huwentoxin-IV into the domain II voltage sensor of Nav1.7. The model predicts that a hydrophobic patch composed of Trp-30 and Phe-6, along with the basic Lys-32 residue, docks into a groove formed by the Nav1.7 S1-S2 and S3-S4 loops. These results provide new insight into the structural and molecular basis of sodium channel block by huwentoxin-IV and may provide a basis for the rational design of toxin-based peptides with improved VGSC potency and/or selectivity.

Results : Key toxin residues and structural features important for activity of are identified. Conclusion : Toxin activity involves a a of basic

An increasing body of evidence suggests that the purinergic receptor P2X, ligand‐gated ion channel, 7 (P2X7) in the CNS may play a key role in neuropsychiatry, neurodegeneration and chronic pain. In this study, we characterized JNJ‐47965567, a centrally permeable, high‐affinity, selective P2X7 antagonist.

Voltage-gated sodium channel 1.7 (Nav1.7) plays a role in the conduction of action potentials and is involved in the sensation of pain. Spider toxins such as Huwentoxin IV (HwTx-IV) are potent inhibitors of Nav1.7, functioning as a gating modifier trapping the voltage sensor in an inward closed conformation. HwTx-IV interacts with specific residues in the voltage sensor S3-S4 region of domain II. The purpose of the present study was to understand the residues important for interaction between HwTx-IV and Nav1.7. Computationally, molecular dynamics was used to study wild type HwTx-IV along with various alanine and cystine mutations to determine residues important for the stability of toxin and to obtain a model of the interacting surface. A homology model of Nav1.7 was built and the toxin docked to determine key interactions. Experimentally, alanine mutants of HwTx-IV were tested for functional activity using FLIPR, QPatch, and manual patch. Computational and experimental results suggest key residues critical for binding of the toxin to Nav1.7, particularly S25, W30 and K32. These studies provide a more clear idea of the nature of interaction between HwTx-IV and Nav1.7 and may therefore be a useful guide in designing novel peptides with improved selectivity for sodium channel subtypes.