Cytokine induced 3-D organotypic psoriasis skin model demonstrates distinct roles for NF-κB and JAK pathways in disease pathophysiology.

Psoriasis vulgaris is an inflammatory skin disease that affects 2%-3% of the population worldwide. One of the major challenges in discovering novel therapies is the poor translatability of animal models to human disease. Therefore, it is imperative to develop human preclinical models of psoriasis that are amenable to pharmacological intervention. Here, we report a 3-D reconstituted human epidermis (RHE) culture system treated with cytokines commonly associated with psoriasis (TNFα, IL-17A and IL-22) that reproduced some key features of the human disease. The effects on epidermal morphology, gene transcription and cytokine production, which are dysregulated in psoriasis were assessed. Certain morphological features of psoriatic epidermis were evident in cytokine-stimulated RHEs, including hypogranulosis and parakeratosis. In addition, RHEs responded to a cytokine mix in a dose-dependent manner by expressing genes and proteins associated with impaired keratinocyte differentiation (keratin 10/K10, loricrin), innate immune responses (S100A7, DEFB4, elafin) and inflammation (IL-1α, IL-6, IL-8, IL-10, IL-12/23p40, IL-36γ, GM-CSF and IFNγ) typical of psoriasis. These disease-relevant changes in morphology, gene transcription and cytokine production were robustly attenuated by pharmacologically blocking TNFα/IL-17A-induced NF-κB activation with IKK-2 inhibitor IV. Conversely, inhibition of IL-22-induced JAK1 signalling with ABT-317 strongly attenuated morphological features of the disease but had no effect on NFκB-dependent cytokine production, suggesting distinct mechanisms of action by the cytokines driving psoriasis. These data support the use of cytokine-induced RHE models for identifying and targeting keratinocyte signalling pathways important for disease progression and may provide translational insights into novel keratinocyte mechanisms for novel psoriasis therapies.

Histologic progression of acne inversa/hidradenitis suppurativa: Implications for future investigations and therapeutic intervention.

Since first recognized in 1839, the pathogenesis of acne inversa (AI) has undergone repeated revisions. Although there is agreement that AI involves occlusion of hair follicles with subsequent inflammation and the formation of tracts, the histologic progression of this disease still requires refinement. The objective of this study was to examine the histologic progression of AI based on the examination of a large cohort of punch biopsies and excisional samples that were examined first by hematoxylin and eosin staining. The most informative of these samples were step-sectioned and stained by immunohistochemistry for epithelial and inflammatory markers. Based on this examination, the following observations were made: 1) AI arises from the epithelium of the infundibulum of terminal and vellus hairs; 2) These form cysts and epithelial tendrils that extend into soft tissue; 3) Immunohistochemical staining demonstrates the epithelium of AI is disordered with infundibular and isthmic differentiation and de novo expression of stem cell markers; 4) The inflammatory response in AI is heterogeneous and largely due to cyst rupture. The conclusions of this investigation were that AI is an epithelial-driven disease caused by infiltrative, cyst forming tendrils and most of the inflammation is due to cyst rupture and release of cornified debris and bacteria. Cyst rupture often occurs below the depths of punch biopsy samples indicating their use for analysis may give an incomplete picture of the disease. Finally, our data suggest that unless therapies inhibit tendril development, it is unlikely they will cause prolonged treatment-induced remission in AI.

Inhibition of Interleukin-23-Mediated Inflammation with a Novel Small Molecule Inverse Agonist of RORγt.

Blockade of interleukin (IL)-23 or IL-17 with biologics is clinically validated as a treatment of psoriasis. However, the clinical impact of targeting other nodes within the IL-23/IL-17 pathway, especially with small molecules, is less defined. We report on a novel small molecule inverse agonist of retinoid acid-related orphan receptor (ROR) γt and its efficacy in preclinical models of psoriasis and arthritis. 1-(2,4-Dichloro-3-((1,4-dimethyl-6-(trifluoromethyl)-1H-indol-2-yl)methyl)benzoyl)piperidine-4-carboxylic acid (A-9758) was optimized from material identified from a high-throughput screening campaign. A-9758 is selective for RORγt and exhibits robust potency against IL-17A release both in vitro and in vivo. In vivo, we also show that IL-23 is sufficient to drive the accumulation of RORγt+ cells, and inhibition of RORγt significantly attenuates IL-23-driven psoriasiform dermatitis. Therapeutic treatment with A-9758 (i.e., delivered during active disease) was also effective in blocking skin and joint inflammation. Finally, A-9758 exhibited efficacy in an ex vivo human whole blood assay, suggesting small molecule inverse agonists of RORγt could be efficacious in human IL-17-related diseases. SIGNIFICANCE STATEMENT: Using a novel small molecule inverse agonist, and preclinical assays, we show that RORγt is a viable target for the inhibition of RORγt/Th17-driven diseases such as psoriasis. Preclinical models of psoriasis show that inhibition of RORγt blocks both the accumulation and effector function of IL-17-producing T cells.

IL-36 receptor antagonistic antibodies inhibit inflammatory responses in preclinical models of psoriasiform dermatitis.

Psoriasis vulgaris (PV) results from activation of IL-23/Th17 immune pathway and is further amplified by cytokines/chemokines from skin cells. Among skin-derived pro-inflammatory cytokines, IL-36 family members are highly upregulated in PV patients and play a critical role in general pustular psoriasis. However, there is limited data showing crosstalk between the IL-23 and IL-36 pathways in PV. Herein, potential attenuation of skin inflammation in the IL-23-induced mouse model of psoriasiform dermatitis by functional inhibition of IL-36 receptor (IL-36R) was interrogated. Anti-mouse IL-36R monoclonal antibodies (mAbs) were generated and validated in vitro by inhibiting IL-36α-induced secretion of CXCL1 from NIH 3T3 cells. Antibody target engagement was demonstrated by inhibition of CXCL1 production in a novel acute model of IL-36α systemic injection in mice. In addition, anti-IL-36R mAbs inhibited tissue inflammation and inflammatory gene expression in an IL-36α ear injection model of psoriasiform dermatitis demonstrating engagement of the target in the ear skin. To elucidate the possible role of IL-36 signalling in IL-23/Th17 pathway, the ability of anti-IL-36R mAbs to inhibit skin inflammation in an IL-23 ear injection model was assessed. Inhibiting the IL-36 pathway resulted in significant attenuation of skin thickening and psoriasis-relevant gene expression. Taken together, these data suggest a role for IL-36 signalling in the IL-23/Th17 signalling axis in PV.

Pharmacological modulation of brain activity in a preclinical model of osteoarthritis.

The earliest stages of osteoarthritis are characterized by peripheral pathology; however, during disease progression chronic pain emerges-a major symptom of osteoarthritis linked to neuroplasticity. Recent clinical imaging studies involving chronic pain patients, including osteoarthritis patients, have demonstrated that functional properties of the brain are altered, and these functional changes are correlated with subjective behavioral pain measures. Currently, preclinical osteoarthritis studies have not assessed if functional properties of supraspinal pain circuitry are altered, and if these functional properties can be modulated by pharmacological therapy either by direct or indirect action on brain systems. In the current study, functional connectivity was first assessed in order to characterize the functional neuroplasticity occurring in the rodent medial meniscus tear (MMT) model of osteoarthritis-a surgical model of osteoarthritis possessing peripheral joint trauma and a hypersensitive pain state. In addition to knee joint trauma at week 3 post-MMT surgery, we observed that supraspinal networks have increased functional connectivity relative to sham animals. Importantly, we observed that early and sustained treatment with a novel, peripherally acting broad-spectrum matrix metalloproteinase (MMP) inhibitor (MMPi) significantly attenuates knee joint trauma (cartilage degradation) as well as supraspinal functional connectivity increases in MMT animals. At week 5 post-MMT surgery, the acute pharmacodynamic effects of celecoxib (selective cyclooxygenase-2 inhibitor) on brain function were evaluated using pharmacological magnetic resonance imaging (phMRI) and functional connectivity analysis. Celecoxib was chosen as a comparator, given its clinical efficacy for alleviating pain in osteoarthritis patients and its peripheral and central pharmacological action. Relative to the vehicle condition, acute celecoxib treatment in MMT animals yielded decreased phMRI infusion responses and decreased functional connectivity, the latter observation being similar to what was detected following chronic MMPi treatment. These findings demonstrate that an assessment of brain function may provide an objective means by which to further evaluate the pathology of an osteoarthritis state as well as measure the pharmacodynamic effects of therapies with peripheral or peripheral and central pharmacological action.

Importance of PLD2 in an IL-23 driven psoriasiform dermatitis model and potential link to human psoriasis.

Phospholipase D2 (PLD2), a major isoform of the PLD family, has been reported to regulate inflammatory responses. Thus far, the relevance of PLD2 in psoriasis, an inflammatory skin disease, has not been explored. In the current study, we examined PLD2 expression in the skin of psoriasis patients and the role of PLD2 in an interleukin (IL)-23-induced mouse model of psoriasiform dermatitis. Both in situ hybridization and bulk RNA sequencing showed PLD2 gene expression is significantly higher in lesional relative to non-lesional skin of psoriasis patients or the skin of healthy subjects. PLD2 expression is also enriched in residual lesions from patients on biologic therapies. Murine in vivo studies showed that PLD2 deficiency significantly reduced psoriasiform inflammation in IL-23-injected ears, as reflected by decreases in ear thickness, expression of defensin beta 4A and the S100 calcium binding protein A7A, macrophage infiltrate, and expression of CXCL10 and IL-6. However, the expression of type 17 cytokines, IL-17A and IL-17F, were not reduced. Dual knockout of PLD1 and PLD2 offered little additional protection compared to PLD2 knockout alone in the IL-23 model. In addition, pharmacological inhibition with a pan-PLD1/PLD2 inhibitor also suppressed IL-23-induced psoriasiform dermatitis. Bone-marrow-derived macrophages from wild type (WT) and PLD2 knockout (KO) mice exhibited little difference in viability and sensitivity to lipopolysaccharide and/or interferon gamma, or resiquimod (R848). PLD2 deficiency did not alter the differentiation and function of Th17 cells in an ex vivo study with splenocytes isolated from WT and PLD2 KO mice. Overall, these data suggest that PLD2 may play a role in the pathophysiology of psoriasis. Reducing macrophage infiltrate and cytokine/chemokine production might contribute to an anti-inflammatory effect observed in PLD2 knockout mice. Further studies are required to better understand the mechanisms by which PLD2 contributes to skin lesions in psoriasis patients and psoriasiform dermatitis models.

Chroman and tetrahydroquinoline ureas as potent TRPV1 antagonists.

Novel chroman and tetrahydroquinoline ureas were synthesized and evaluated for their activity as TRPV1 antagonists. It was found that aryl substituents on the 7- or 8-position of both bicyclic scaffolds imparted the best in vitro potency at TRPV1. The most potent chroman ureas were assessed in chronic and acute pain models, and compounds with the ability to cross the blood-brain barrier were shown to be highly efficacious. The tetrahydroquinoline ureas were found to be potent CYP3A4 inhibitors, but replacement of bulky substituents at the nitrogen atom of the tetrahydroisoquinoline moiety with small groups such as methyl can minimize the inhibition.

Phospholipase A2 enzymes represent a shared pathogenic pathway in psoriasis and pityriasis rubra pilaris.

Altered epidermal differentiation along with increased keratinocyte proliferation is a characteristic feature of psoriasis and pityriasis rubra pilaris (PRP). However, despite this large degree of overlapping clinical and histologic features, the molecular signatures these skin disorders share are unknown. Using global transcriptomic profiling, we demonstrate that plaque psoriasis and PRP skin lesions have high overlap, with all differentially expressed genes in PRP relative to normal skin having complete overlap with those in psoriasis. The major common pathway shared between psoriasis and PRP involves the phospholipases PLA2G2F, PLA2G4D, and PLA2G4E, which were found to be primarily expressed in the epidermis. Gene silencing each of the 3 PLA2s led to reduction in immune responses and epidermal thickness both in vitro and in vivo in a mouse model of psoriasis, establishing their proinflammatory roles. Lipidomic analyses demonstrated that PLA2s affect mobilization of a phospholipid-eicosanoid pool, which is altered in psoriatic lesions and functions to promote immune responses in keratinocytes. Taken together, our results highlight the important role of PLA2s as regulators of epidermal barrier homeostasis and inflammation, identify PLA2s as a shared pathogenic mechanism between PRP and psoriasis, and as potential therapeutic targets for both diseases.

Discovery of TRPV1 antagonist ABT-116.

The synthesis and SAR of a series of indazole TRPV1 antagonists leading to the discovery of 21 (ABT-116) is described. Biological studies demonstrated potent in vitro and in vivo activity for 21, as well as suitable physicochemical and pharmacokinetic properties for advancement to clinical development for pain management.

Subtype-selective Na(v)1.8 sodium channel blockers: identification of potent, orally active nicotinamide derivatives.

A series of aryl-substituted nicotinamide derivatives with selective inhibitory activity against the Na(v)1.8 sodium channel is reported. Replacement of the furan nucleus and homologation of the anilide linker in subtype-selective blocker A-803467 (1) provided potent, selective derivatives with improved aqueous solubility and oral bioavailability. Representative compounds from this series displayed efficacy in rat models of inflammatory and neuropathic pain.

Discovery and biological evaluation of potent, selective, orally bioavailable, pyrazine-based blockers of the Na(v)1.8 sodium channel with efficacy in a model of neuropathic pain.

Na(v)1.8 (also known as PN3) is a tetrodotoxin-resistant (TTx-r) voltage-gated sodium channel (VGSC) that is highly expressed on small diameter sensory neurons. It has been implicated in the pathophysiology of inflammatory and neuropathic pain, and we envisioned that selective blockade of Na(v)1.8 would be analgesic, while reducing adverse events typically associated with non-selective VGSC blocking therapeutic agents. Herein, we describe the preparation and characterization of a series of 6-aryl-2-pyrazinecarboxamides, which are potent blockers of the human Na(v)1.8 channel and also block TTx-r sodium currents in rat dorsal root ganglia (DRG) neurons. Selected derivatives display selectivity versus human Na(v)1.2. We further demonstrate that an example from this series is orally bioavailable and produces antinociceptive activity in vivo in a rodent model of neuropathic pain following oral administration.

Characterization of a cannabinoid CB2 receptor-selective agonist, A-836339 [2,2,3,3-tetramethyl-cyclopropanecarboxylic acid [3-(2-methoxy-ethyl)-4,5-dimethyl-3H-thiazol-(2Z)-ylidene]-amide], using in vitro pharmacological assays, in vivo pain models, and pharmacological magnetic resonance imaging.

Studies demonstrating the antihyperalgesic and antiallodynic effects of cannabinoid CB(2) receptor activation have been largely derived from the use of receptor-selective ligands. Here, we report the identification of A-836339 [2,2,3,3-tetramethyl-cyclopropanecarboxylic acid [3-(2-methoxy-ethyl)-4,5-dimethyl-3H-thiazol-(2Z)-ylidene]-amide], a potent and selective CB(2) agonist as characterized in in vitro pharmacological assays and in in vivo models of pain and central nervous system (CNS) behavior models. In radioligand binding assays, A-836339 displays high affinities at CB(2) receptors and selectivity over CB(1) receptors in both human and rat. Likewise, A-836339 exhibits high potencies at CB(2) and selectivity over CB(1) receptors in recombinant fluorescence imaging plate reader and cyclase functional assays. In addition A-836339 exhibits a profile devoid of significant affinity at other G-protein-coupled receptors and ion channels. A-836339 was characterized extensively in various animal pain models. In the complete Freund's adjuvant model of inflammatory pain, A-836339 exhibits a potent CB(2) receptor-mediated antihyperalgesic effect that is independent of CB(1) or mu-opioid receptors. A-836339 has also demonstrated efficacies in the chronic constrain injury (CCI) model of neuropathic pain, skin incision, and capsaicin-induced secondary mechanical hyperalgesia models. Furthermore, no tolerance was developed in the CCI model after subchronic treatment with A-836339 for 5 days. In assessing CNS effects, A-836339 exhibited a CB(1) receptor-mediated decrease of spontaneous locomotor activities at a higher dose, a finding consistent with the CNS activation pattern observed by pharmacological magnetic resonance imaging. These data demonstrate that A-836339 is a useful tool for use of studying CB(2) receptor pharmacology and for investigation of the role of CB(2) receptor modulation for treatment of pain in preclinical animal models.

IL-23 induces regulatory T cell plasticity with implications for inflammatory skin diseases.

Foxp3+ regulatory T cells (Tregs) represent a major fraction of skin resident T cells. Although normally protective, Tregs have been shown to produce pro-inflammatory cytokines in human diseases, including psoriasis. A significant hurdle in the Treg field has been the identification, or development, of model systems to study this Treg plasticity. To overcome this gap, we analyzed skin resident Tregs in a mouse model of IL-23 mediated psoriasiform dermatitis. Our results demonstrate that IL-23 drove the accumulation of Tregs; including a subpopulation that co-expressed RORγt and produced IL-17A. Genesis of this population was attenuated by a RORγt inverse agonist compound and clinically relevant therapeutics. In vitro, IL-23 drove the generation of CD4+Foxp3+RORγt+IL-17A+ cells from Treg cells. Collectively, our data shows that IL-23 drives Treg plasticity by inducing a population of CD4+Foxp3+RORγt+IL-17A+ cells that could play a role in the disease pathogenesis. Through this work, we define an in vitro system and a pre-clinical in vivo mouse model that can be used to further study Treg homeostasis and plasticity in the context of psoriasis.

Monocytes/Macrophages play a pathogenic role in IL-23 mediated psoriasis-like skin inflammation.

Psoriasis is an immune-mediated inflammatory skin disease that affects millions worldwide. Studying immune cells involved in psoriasis pathogenesis is essential to identify effective and safe therapeutics for the disease. Using human psoriasis skin, activated macrophages were observed in both lesional and non-lesional skin, but were elevated in lesional skin. Activation of the IL-23/IL-17 pathway is integral to the development of psoriasis. To further characterize the monocyte/macrophage (Mon/Mac) population when the IL-23 pathway is activated, a murine model of intradermal injection of IL-23 was used. Flow cytometry revealed that Mon/Mac cells were the dominant immune population, particularly late in the model, highlighted by strong presence of Ly6ChiMHC IIhi cells. The Mon/Mac cells were also shown to have high expression for TNFα but not IL-17A. Prophylactic dosing of a CSF-1R inhibitor to deplete Mon/Mac cells significantly reduced several inflammatory mediators from the skin tissue suggesting a pathogenic role for Mon/Mac. Treatment dosing of the inhibitor produced a less robust effect. Mon/Mac cells were also differentiated by levels of Ki67 and TNFα expression. These data point to an important contribution of Mon/Mac cells in IL-23 related skin inflammation and suggest that these cells are a significant player in the underlying pathophysiology of psoriasis.

Characterization of psoriasiform dermatitis induced by systemic injection of interleukin-23 minicircles in mice.

The interleukin (IL)-23/IL-17 axis plays a central role in the pathogenesis of psoriasis and is elevated in lesional psoriatic skin. Different murine models have been developed to mimic this pathophysiology each carrying specific merits and limitations. In an attempt to address some of these limitations, B10.RIII mice received a single hydrodynamic injection of IL-23 minicircles (MC) to induce hepatic transcription and the endogenous production of IL-23. Plasma and ear IL-23 levels were dose-dependently (0.3-3 µg) increased in MC injected mice and were sustained over the 14-day study duration. Beginning on day 7 post-injection, mice developed dose-related ear inflammation, histologically confirmed increases in epidermal and dermal area, as well as enhanced neutrophil and macrophage content. Flow cytometry demonstrated increased levels of granulocytes, T cells and monocytes/macrophages in the ear skin, with T cells identified as the main cellular source of IL-17A. Evaluation of mRNA and protein showed time-dependent, increased levels of the IL-23/IL-17 pathway and inflammatory/microbial cytokines/chemokines in the ear which differed kinetically from circulating levels. An anti-IL-23p40 antibody was assessed following both prophylactic administration and administration once the disease was established. Prophylactic dosing completely prevented the development of the ear phenotype across endpoints. Treatment administration showed a dose-related response, with a maximum inhibition of 64-94%, depending on endpoint. These data demonstrate that the IL-23 MC model is a useful approach to study IL-23/IL-17-driven skin inflammation and may facilitate preclinical assessment of novel therapies.

Small Molecule IL-36γ Antagonist as a Novel Therapeutic Approach for Plaque Psoriasis.

IL-36 cytokines are pro-inflammatory members of the IL-1 family that are upregulated in inflammatory disorders. Specifically, IL-36γ is highly expressed in active psoriatic lesions and can drive pro-inflammatory processes in 3D human skin equivalents supporting a role for this target in skin inflammation. Small molecule antagonists of interleukins have been historically challenging to generate. Nevertheless, we performed a small molecule high-throughput screen to identify IL-36 antagonists using a novel TR-FRET binding assay. Several compounds, including 2-oxypyrimidine containing structural analogs of the marketed endothelin receptor A antagonist Ambrisentan, were identified as hits from the screen. A-552 was identified as a the most potent antagonist of human IL-36γ, but not the closely related family member IL-36α, was capable of attenuating IL-36γ induced responses in mouse and human disease models. Additionally, x-ray crystallography studies identified key amino acid residues in the binding pocket present in human IL-36γ that are absent in human IL-36α. A-552 represents a first-in-class small molecule antagonist of IL-36 signaling that could be used as a chemical tool to further investigate the role of this pathway in inflammatory skin diseases such as psoriasis.

Painful purinergic receptors.

Multiple P2 receptor-mediated mechanisms exist by which ATP can alter nociceptive sensitivity following tissue injury. Evidence from a variety of experimental strategies, including genetic disruption studies and the development of selective antagonists, has indicated that the activation of P2X receptor subtypes, including P2X(3), P2X(2/3), P2X(4) and P2X(7), and P2Y (e.g., P2Y(2)) receptors, can modulate pain. For example, administration of a selective P2X(3) antagonist, A-317491, has been shown to effectively block both hyperalgesia and allodynia in different animal models of pathological pain. Intrathecally delivered antisense oligonucleotides targeting P2X(4) receptors decrease tactile allodynia following nerve injury. Selective antagonists for the P2X(7) receptor also reduce sensitization in animal models of inflammatory and neuropathic pain, providing evidence that purinergic glial-neural interactions are important modulators of noxious sensory neurotransmission. Furthermore, activation of P2Y(2) receptors leads to sensitization of polymodal transient receptor potential-1 receptors. Thus, ATP acting at multiple purinergic receptors, either directly on neurons (e.g., P2X(3), P2X(2/3), and P2Y receptors) or indirectly through neural-glial cell interactions (P2X(4) and P2X(7) receptors), alters nociceptive sensitivity. The development of selective antagonists for some of these P2 receptors has greatly aided investigations into the nociceptive role of ATP. This perspective highlights some of the recent advances to identify selective P2 receptor ligands, which has enhanced the investigation of ATP-related modulation of pain sensitivity.

(R)-(5-tert-butyl-2,3-dihydro-1H-inden-1-yl)-3-(1H-indazol-4-yl)-urea (ABT-102) blocks polymodal activation of transient receptor potential vanilloid 1 receptors in vitro and heat-evoked firing of spinal dorsal horn neurons in vivo.

The transient receptor potential vanilloid (TRPV) 1 receptor, a nonselective cation channel expressed on peripheral sensory neurons and in the central nervous system, plays a key role in pain. TRPV1 receptor antagonism is a promising approach for pain management. In this report, we describe the pharmacological and functional characteristics of a structurally novel TRPV1 antagonist, (R)-(5-tert-butyl-2,3-dihydro-1H-inden-1-yl)-3-(1H-indazol-4-yl)-urea (ABT-102), which has entered clinical trials. At the recombinant human TRPV1 receptor ABT-102 potently (IC(50) = 5-7 nM) inhibits agonist (capsaicin, N-arachidonyl dopamine, anandamide, and proton)-evoked increases in intracellular Ca(2+) levels. ABT-102 also potently (IC(50) = 1-16 nM) inhibits capsaicin-evoked currents in rat dorsal root ganglion (DRG) neurons and currents evoked through activation of recombinant rat TRPV1 currents by capsaicin, protons, or heat. ABT-102 is a competitive antagonist (pA(2) = 8.344) of capsaicin-evoked increased intracellular Ca(2+) and shows high selectivity for blocking TRPV1 receptors over other TRP receptors and a range of other receptors, ion channels, and transporters. In functional studies, ABT-102 blocks capsaicin-evoked calcitonin gene-related peptide release from rat DRG neurons. Intraplantar administration of ABT-102 blocks heat-evoked firing of wide dynamic range and nociceptive-specific neurons in the spinal cord dorsal horn of the rat. This effect is enhanced in a rat model of inflammatory pain induced by administration of complete Freund's adjuvant. Therefore, ABT-102 potently blocks multiple modes of TRPV1 receptor activation and effectively attenuates downstream consequences of receptor activity. ABT-102 is a novel and selective TRPV1 antagonist with pharmacological and functional properties that support its advancement into clinical studies.

Structure-activity relationship studies on N'-aryl carbohydrazide P2X7 antagonists.

N'-aryl acyl hydrazides were identified as P2X7 receptor antagonists. Structure-activity relationship (SAR) studies evaluated functional activity by monitoring calcium flux inhibition in cell lines expressing recombinant human and rat P2X7 receptors. Selected analogs were assayed in vitro for their capacity to inhibit release of cytokine IL-1beta. Compounds with potent antagonist function were evaluated in vivo using the zymosan-induced peritonitis model. A representative compound effectively attenuated mechanical allodynia in a rat model of neuropathic pain.

Identification of (R)-1-(5-tert-butyl-2,3-dihydro-1H-inden-1-yl)-3-(1H-indazol-4-yl)urea (ABT-102) as a potent TRPV1 antagonist for pain management.

Vanilloid receptor TRPV1 is a cation channel that can be activated by a wide range of noxious stimuli, including capsaicin, acid, and heat. Blockade of TRPV1 activation by selective antagonists is under investigation by several pharmaceutical companies in an effort to identify novel agents for pain management. Here we report that replacement of substituted benzyl groups by an indan rigid moiety in a previously described N-indazole- N'-benzyl urea series led to a number of TRPV1 antagonists with significantly increased in vitro potency and enhanced drug-like properties. Extensive evaluation of pharmacological, pharmacokinetic, and toxicological properties of synthesized analogs resulted in identification of ( R)-7 ( ABT-102). Both the analgesic activity and drug-like properties of ( R)-7 support its advancement into clinical pain trials.