The AMPA receptor (AMPARs) mediates fast excitatory neurotransmission and is the central to synaptic plasticity, learning and memory dysregulation of this system has been implicated in epilepsy, neurodegeneration, and neuropsychiatric disorders. The transmembrane AMPA receptor regulatory protein γ8 (TARP γ8) plays a crucial role in the expression and localization of AMPARs within the brain, particularly in the hippocampus and cortex. A selective positron emission tomography (PET) ligand to image this target is of significant interest for investigating potential clinical AMPAR/TARP γ8 antagonists. This study describes the development and preclinical evaluation of a potent and selective tracer targeting TARP γ8, [18F]JNJ-1. The binding potency of JNJ-1 was evaluated using a calcium flux assay in HEK-293 cells. The radiotracer was synthesized on an automated synthesizer via a one-step substitution. TARP γ8 target expression in brains was confirmed through immunohistochemistry (IHC), and adjacent brain sections were used for autoradiography (ARG). In vivo assays were conducted in rats, knockout mice, and non-human primates by [18F]JNJ-1 PET imaging and JNJ-1 microdosing studies. JNJ-1 exhibited very high binding potency to TARP γ8, IC50 = 50 pM. Immunoreactivity of TARP γ8 showed high intensity in the hippocampus and moderate levels in the cortex across mouse, rat, and monkey brains. A microdosing with JNJ-1 study revealed high, moderate, and low levels of JNJ-1 uptake in the hippocampus, cortex, and cerebellum, respectively in wild-type mice (γ8 + / +), and low levels in all regions in knockout (γ8 − / −) mouse brains. In vitro ARG of [18F]JNJ-1 corresponded with IHC staining on adjacent rat brain sections, and the signal being blocked by JNJ-2, a potent and selective antagonist of TARP γ8. In vivo PET imaging demonstrated high brain uptake in the expected areas in rats and monkeys, which was blockable by JNJ-2 in a dose-dependent manner. [18F]JNJ-1 is emerging as a promising PET tracer with high in vitro binding affinity and evidence suggestive of target engagement at AMPAR/TARP γ8. The process of clinical validation is presently underway.

The ability to rapidly navigate a wide diversity of chemical space from simple building blocks is a cornerstone of medicinal chemistry campaigns. Aza-bicyclo[2.1.1]hexane (aza-BCH) and bicyclo[1.1.1]pentane (BCP) scaffolds have recently emerged as attractive classes of sp3-rich cores for replacing flat, aromatic scaffolds with metabolically resistant, three-dimensional frameworks. Over the last decade, these pharmaceutically desirable properties and increased synthetic accessibility have led to a marked increase in the adoption of aza-BCHs and BCPs into drug scaffolds. While multiple, independent methods have been developed for the preparation of these structural motifs, strategies to directly convert, or scaffold hop, between these bioisosteric subclasses through single-atom skeletal editing would enable efficient interpolation within this valuable chemical space. Herein, we describe a strategy to scaffold hop between aza-BCH and BCP cores through a nitrogen-deleting skeletal edit. Photochemical [2+2] cycloadditions, used to prepare multifunctionalized aza-BCH frameworks, are coupled with a subsequent deamination step to afford bridge-functionalized BCPs, for which few synthetic solutions currently exist. The modular sequence provides access to various privileged bridged bicycles of pharmaceutical relevance bearing substituents that can be further derivatized.

Correction for 'Convergent synthesis of thiodiazole dioxides from simple ketones and amines through an unusual nitrogen-migration mechanism' by Kunlayanee Punjajom et al., Chem. Sci., 2024, 15, 328-335, https://doi.org/10.1039/D3SC04478E.

Correction for ‘Convergent synthesis of thiodiazole dioxides from simple ketones and amines through an unusual nitrogen-migration mechanism’ by Kunlayanee Punjajom et al., Chem. Sci., 2024, 15, 328–335, https://doi.org/10.1039/D3SC04478E.

We report the modular preparation of dihydro-1,2,5-thiodiazole dioxide heterocycles starting from methyl ketones and primary amines. This one-pot, three-component coupling employs 2,3-dimethylimidazole-1-sulfonyl azide triflate as a coupling reagent and oxidant. The transformation is scalable and various ketones and amines can be used, yielding thiodiazole dioxide products in up to 89% yield. In addition, 15N- and 13C-labeling studies suggest a mechanism involving a 1,2-nitrogen migration. Together with the mechanistic studies, DFT calculations provide insight into the reaction pathway and set the stage for further exploration of the mechanistic nuances of reactions that use sulfamoyl azides. In combination with the demonstrated modularity of the approach reported herein, the derivatization of the thiodiazole dioxide products highlights the potential of this methodology to rapidly access diverse chemical structures.

Azabicyclo[2.1.1]hexanes (aza-BCHs) and bicyclo[1.1.1]pentanes (BCPs) have emerged as attractive classes of sp3-rich cores for replacing flat, aromatic groups with metabolically resistant, three-dimensional frameworks in drug scaffolds. Strategies to directly convert, or "scaffold hop", between these bioisosteric subclasses through single-atom skeletal editing would enable efficient interpolation within this valuable chemical space. Herein, we describe a strategy to "scaffold hop" between aza-BCH and BCP cores through a nitrogen-deleting skeletal edit. Photochemical [2+2] cycloadditions, used to prepare multifunctionalized aza-BCH frameworks, are coupled with a subsequent deamination step to afford bridge-functionalized BCPs, for which few synthetic solutions currently exist. The modular sequence provides access to various privileged bridged bicycles of pharmaceutical relevance.

The Drug Design Data Resource (D3R) aims to identify best practice methods for computer aided drug design through blinded ligand pose prediction and affinity challenges. Herein, we report on the results of Grand Challenge 4 (GC4). GC4 focused on proteins beta secretase 1 and Cathepsin S, and was run in an analogous manner to prior challenges. In Stage 1, participant ability to predict the pose and affinity of BACE1 ligands were assessed. Following the completion of Stage 1, all BACE1 co-crystal structures were released, and Stage 2 tested affinity rankings with co-crystal structures. We provide an analysis of the results and discuss insights into determined best practice methods.

Cathepsin S (CatS) is a cysteine protease found in lysosomes of hematopoietic and microglial cells and in secreted form in the extracellular space. While CatS has been shown to contribute significantly to neuropathic pain, the precise mechanisms remain unclear. In this report, we describe JNJ-39641160, a novel non-covalent, potent, selective and orally-available CatS inhibitor that is peripherally restricted (non-CNS penetrant) and may represent an innovative class of immunosuppressive and analgesic compounds and tools useful toward investigating peripheral mechanisms of CatS in neuropathic pain. In C57BL/6 mice, JNJ-39641160 dose-dependently blocked the proteolysis of the invariant chain, and inhibited both T-cell activation and antibody production to a vaccine antigen. In the spared nerve injury (SNI) model of chronic neuropathic pain, in which T-cell activation has previously been demonstrated to be a prerequisite for the development of pain hypersensitivity, JNJ-39641160 fully reversed tactile allodynia in wild-type mice but was completely ineffective in the same model in CatS knockout mice (which exhibited a delayed onset in allodynia). By contrast, in the acute mild thermal injury (MTI) model, JNJ-39641160 only weakly attenuated allodynia at the highest dose tested. These findings support the hypothesis that blockade of peripheral CatS alone is sufficient to fully reverse allodynia following peripheral nerve injury and suggest that the mechanism of action likely involves interruption of T-cell activation and peripheral cytokine release. In addition, they provide important insights toward the development of selective CatS inhibitors for the treatment of neuropathic pain in humans.

The serine hydrolase monoacylglycerol lipase (MAGL) is the rate-limiting enzyme responsible for the degradation of the endocannabinoid 2-arachidonoylglycerol (2-AG) into arachidonic acid and glycerol. Inhibition of 2-AG degradation leads to elevation of 2-AG, the most abundant endogenous agonist of the cannabinoid receptors (CBs) CB1 and CB2. Activation of these receptors has demonstrated beneficial effects on mood, appetite, pain, and inflammation. Therefore, MAGL inhibitors have the potential to produce therapeutic effects in a vast array of complex human diseases. The present report describes the pharmacologic characterization of [1-(4-fluorophenyl)indol-5-yl]-[3-[4-(thiazole-2-carbonyl)piperazin-1-yl]azetidin-1-yl]methanone (JNJ-42226314), a reversible and highly selective MAGL inhibitor. JNJ-42226314 inhibits MAGL in a competitive mode with respect to the 2-AG substrate. In rodent brain, the compound time- and dose-dependently bound to MAGL, indirectly led to CB1 occupancy by raising 2-AG levels, and raised norepinephrine levels in cortex. In vivo, the compound exhibited antinociceptive efficacy in both the rat complete Freund's adjuvant-induced radiant heat hypersensitivity and chronic constriction injury-induced cold hypersensitivity models of inflammatory and neuropathic pain, respectively. Though 30 mg/kg induced hippocampal synaptic depression, altered sleep onset, and decreased electroencephalogram gamma power, 3 mg/kg still provided approximately 80% enzyme occupancy, significantly increased 2-AG and norepinephrine levels, and produced neuropathic antinociception without synaptic depression or decreased gamma power. Thus, it is anticipated that the profile exhibited by this compound will allow for precise modulation of 2-AG levels in vivo, supporting potential therapeutic application in several central nervous system disorders. SIGNIFICANCE STATEMENT: Potentiation of endocannabinoid signaling activity via inhibition of the serine hydrolase monoacylglycerol lipase (MAGL) is an appealing strategy in the development of treatments for several disorders, including ones related to mood, pain, and inflammation. [1-(4-Fluorophenyl)indol-5-yl]-[3-[4-(thiazole-2-carbonyl)piperazin-1-yl]azetidin-1-yl]methanone is presented in this report to be a novel, potent, selective, and reversible noncovalent MAGL inhibitor that demonstrates dose-dependent enhancement of the major endocannabinoid 2-arachidonoylglycerol as well as efficacy in models of neuropathic and inflammatory pain.

The Drug Design Data Resource aims to test and advance the state of the art in protein-ligand modeling by holding community-wide blinded, prediction challenges. Here, we report on our third major round, Grand Challenge 3 (GC3). Held 2017-2018, GC3 centered on the protein Cathepsin S and the kinases VEGFR2, JAK2, p38-α, TIE2, and ABL1, and included both pose-prediction and affinity-ranking components. GC3 was structured much like the prior challenges GC2015 and GC2. First, Stage 1 tested pose prediction and affinity ranking methods; then all available crystal structures were released, and Stage 2 tested only affinity rankings, now in the context of the available structures. Unique to GC3 was the addition of a Stage 1b self-docking subchallenge, in which the protein coordinates from all of the cocrystal structures used in the cross-docking challenge were released, and participants were asked to predict the pose of CatS ligands using these newly released structures. We provide an overview of the outcomes and discuss insights into trends and best-practices.

BackgroundThe α‐amino‐3‐hydroxyl‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) subtype of ionotropic glutamate receptors mediates the majority of fast synaptic transmission within the mammalian brain. The ubiquitous expression of the primary subunits of AMPA receptors (AMPARs), and the lack of pharmacological selectivity amongst them, preclude regional or neuronal subtype specificity. In vivo, AMPARs comprise a variety of accessory proteins. Of particular interest, TARP‐γ8 is highly expressed in the hippocampus, a region of the brain implicated in several psychiatric and neurological disorders.MethodsWe used high‐throughput screening to discover compounds that selectively modulate AMPARs containing TARP‐γ8. Subsequent medicinal chemistry efforts were used to improve potency and pharmacokinetics of the hits. Assays were developed to measure target occupancy and functional effects of the compounds in vivo.ResultsThese compounds possess a novel mechanism‐of‐action consistent with a partial attenuation of the interaction between the TARP and the pore‐forming subunits of the channel. Lead molecules with oral bioavailability and high brain penetration allowed demonstration of a strong relationship between pharmacokinetics and pharmacodynamics. The compounds show anticonvulsant and anxiolytic profiles in rodent. Molecules in this class provide large safety margins in preclinical species relative to non‐specific AMPAR antagonists due to the improved regional specificity of TARP‐γ8 modulators.ConclusionsAMPAR modulators selective for TARP‐γ8 have the potential to be novel treatments for anxiety/depression, bipolar disorder, temporal lobe epilepsy, and/or prodromal schizophrenia. This project also represents proof‐of‐concept for pharmacological targeting of accessory proteins and small‐molecule modulation of protein‐protein interactions.Support or Funding InformationAuthors are employees of Janssen R & D, LLCThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

This report discloses the discovery and characterization of imidazo[1,2-a]pyrazines and pyrazolo[1,5-c]pyrimidines as selective negative modulators of α-amino-3-hydroxy-5-methylisoxazole-4-propionate receptors (AMPARs) associated with transmembrane AMPAR regulatory protein γ-8. Imidazopyrazine 5 was initially identified as a promising γ-8 selective high-throughput screening hit, and subsequent structure-activity relationship optimization yielded subnanomolar, brain penetrant leads. Replacement of the imidazopyrazine core with an isosteric pyrazolopyrimidine scaffold improved microsomal stability and efflux liabilities to provide 26, JNJ-61432059. Following oral administration, 26 exhibited time- and dose-dependent AMPAR/γ-8 receptor occupancy in mouse hippocampus, which resulted in robust seizure protection in corneal kindling and pentylenetetrazole (PTZ) anticonvulsant models.

Glutamate mediates fast excitatory neurotransmission via ionotropic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. The trafficking and gating properties of AMPA receptors (AMPARs) can be amplified by transmembrane AMPAR regulatory proteins (TARPs), which are often expressed in localized brain regions. Herein, we describe the discovery, lead optimization, and preclinical characterization of 5-arylbenzimidazolone and oxindole-based negative modulators of AMPARs associated with TARP γ-8, the primary TARP found in hippocampus. High-throughput screen lead 4 was optimized for potency and brain penetration to provide benzimidazolone 3, JNJ-55511118.1 Replacement of the benzimidazolone core in 3 with an oxindole mitigated reactive metabolite formation and led to the identification of 18 (GluA1/γ-8 pIC50 = 9.7). Following oral dosing in rats, 18 demonstrated robust target engagement in hippocampus as assessed by ex vivo autoradiography (ED50 = 0.6 mg/kg, plasma EC50 = 9 ng/mL).

Mood disorders can be considered as imbalances in the activity of specific neuronal circuits. The alpha-amino-3-hydroxyl-5-methyl-4-isoxazolepropionic acid (AMPA) subtype of ionotropic glutamate receptors mediates the majority of fast synaptic transmission within the mammalian brain. The ubiquitous expression of the primary subunits of AMPA receptors (AMPARs), and the lack of pharmacological selectivity amongst them, preclude regional or neuronal subtype specificity. In vivo, AMPARs comprise a variety of accessory proteins. Of particular interest, TARP-gamma8 is highly expressed in the hippocampus, part of the limbic circuitry that putatively is overactive in recurrent mood disorders.

Members of the α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionic acid (AMPA) subtype of ionotropic glutamate receptors mediate the majority of fast synaptic transmission within the mammalian brain and spinal cord, representing attractive targets for therapeutic intervention. Here, we describe novel AMPA receptor modulators that require the presence of the accessory protein CACNG8, also known as transmembrane AMPA receptor regulatory protein γ8 (TARP-γ8). Using calcium flux, radioligand binding, and electrophysiological assays of wild-type and mutant forms of TARP-γ8, we demonstrate that these compounds possess a novel mechanism of action consistent with a partial disruption of the interaction between the TARP and the pore-forming subunit of the channel. One of the molecules, 5-[2-chloro-6-(trifluoromethoxy)phenyl]-1,3-dihydrobenzimidazol-2-one (JNJ-55511118), had excellent pharmacokinetic properties and achieved high receptor occupancy following oral administration. This molecule showed strong, dose-dependent inhibition of neurotransmission within the hippocampus, and a strong anticonvulsant effect. At high levels of receptor occupancy in rodent in vivo models, JNJ-55511118 showed a strong reduction in certain bands on electroencephalogram, transient hyperlocomotion, no motor impairment on rotarod, and a mild impairment in learning and memory. JNJ-55511118 is a novel tool for reversible AMPA receptor inhibition, particularly within the hippocampus, with potential therapeutic utility as an anticonvulsant or neuroprotectant. The existence of a molecule with this mechanism of action demonstrates the possibility of pharmacological targeting of accessory proteins, increasing the potential number of druggable targets.

The synthesis, SAR, and preclinical characterization of a series of substituted 6,7-dihydro[1,2,4]triazolo[4,3]pyrazin-8(5H)-one P2X7 receptor antagonists are described. Optimized leads from this series comprise some of the most potent human P2X7R antagonists reported to date (IC50s<1nM). They also exhibit sufficient potency and oral bioavailability in rat to enable extensive in vivo profiling. Although many of the disclosed compounds are peripherally restricted, compound 11d is brain penetrant and upon oral administration demonstrated dose-dependent target engagement in rat hippocampus as determined by ex vivo receptor occupancy with radiotracer 5 (ED50=0.8mg/kg).

The ATP-gated ion channel P2X7 has emerged as a potential central nervous system (CNS) drug target based on the hypotheses that pro-inflammatory cytokines such as IL-1β that are released by microglia, may contribute to the etiology of various disorders of the CNS including depression. In this study, we identified two closely related P2X7 antagonists, JNJ-54232334 and JNJ-54140515, and then tritium labeled the former to produce a new radioligand for P2X7. JNJ-54232334 is a high affinity ligand for the rat P2X7 with a pKi of 9.3±0.1. In rat cortical membranes, [3H] JNJ-54232334 reached saturable binding with equilibrium dissociation (Kd) constant of 4.9±1.3 nM. The compound displayed monophasic association and dissociation kinetics with fast on and off rates. In rat brain sections, specific binding of [3H] JNJ-54232334 was markedly improved compared to the previously described P2X7 radioligand, [3H] A-804598. In P2X7 knockout mouse brain sections, [3H] A-804598 bound to non-P2X7 binding sites in contrast to [3H] JNJ-54232334. In rat or wild type mouse brain sections [3H] JNJ-54232334 bound in a more homogenous and region independent manner. The ubiquitous expression of P2X7 receptors was confirmed with immunohistochemistry in rat brain sections. The partial displacement of [3H] A-804598 binding resulted in the underestimation of the level of ex vivo P2X7 occupancy for JNJ-54140515. Higher levels of P2X7 ex vivo occupancy were measured using [3H] JNJ-54232334 due to less non-specific binding. In summary, we describe [3H] JNJ-54232334 as a novel P2X7 radioligand, with improved properties over [3H] A-804598.