Identification of (R)-(2-Chloro-3-(trifluoromethyl)phenyl)(1-(5-fluoropyridin-2-yl)-4-methyl-6,7-dihydro-1H-imidazo[4,5-c]pyridin-5(4H)-yl)methanone (JNJ 54166060), a Small Molecule Antagonist of the P2X7 receptor

Techniques for evaluating the ATP-gated ion channel P2X7 receptor function in macrophages and microglial cells

Resident macrophages are tissue-specific innate immune cells acting as sentinels, constantly patrolling their assigned tissue to maintain homeostasis, and quickly responding to pathogenic invaders or molecular danger signals molecules when necessary. Adenosine triphosphate (ATP), when released to the extracellular medium, acts as a danger signal through specific purinergic receptors. Interaction of ATP with the purinergic receptor P2X7 activates macrophages and microglial cells in different pathological conditions, triggering inflammation. The highly expressed P2X7 receptor in these cells induces cell membrane permeabilization, inflammasome activation, cell death, and the production of inflammatory mediators, including cytokines and nitrogen and oxygen-reactive species. This review explores the techniques to evaluate the functional and molecular aspects of the P2X7 receptor, particularly in macrophages and microglial cells. Polymerase chain reaction (PCR), Western blotting, and immunocytochemistry or immunohistochemistry are essential for assessing gene and protein expression in these cell types. Evaluation of P2X7 receptor function involves the use of ATP and selective agonists and antagonists and diverse techniques, including electrophysiology, intracellular calcium measurements, ethidium bromide uptake, and propidium iodide cell viability assays. These techniques are crucial for studying the role of P2X7 receptors in immune responses, neuroinflammation, and various pathological conditions. Therefore, a comprehensive understanding of the functional and molecular aspects of the P2X7 receptor in macrophages and microglia is vital for unraveling its involvement in immune modulation and its potential as a therapeutic target. The methodologies presented and discussed herein offer valuable tools for researchers investigating the complexities of P2X7 receptor signaling in innate immune cells in health and disease.

Synthetic molecules as P2X7 receptor antagonists: A medicinal chemistry update focusing the therapy of inflammatory diseases

Stimulation of the P2X7 receptor by extracellular adenosine 5'-triphosphate induces a series of responses in the organism, exceptionally protein cascades related to the proinflammatory process. This has made P2X7 a target for research on inflammatory diseases such as rheumatoid arthritis. Thus, the incessant search for new prototypes that aim to antagonize the action of P2X7 has been remarkable in recent decades, a factor that has already led to numerous clinical studies in humans. In this review, we present the key molecules developed over the years with potential inhibition of P2X7 and inflammation. In addition, an update with newly developed chemical classes with promising activity and results in clinical studies for human pathologies focusing on P2X7 inhibition.

Leveraging the ATP-P2X7 receptor signalling axis to alleviate traumatic CNS damage and related complications

The P2X7 receptor is an exceptional member of the P2X purinergic receptor family, with its activation requiring high concentrations of extracellular adenosine 5'-triphosphate (ATP) that are often associated with tissue damage and inflammation. In the central nervous system (CNS), it is highly expressed in glial cells, particularly in microglia. In this review, we discuss the role and mechanisms of the P2X7 receptor in mediating neuroinflammation and other pathogenic events in a variety of traumatic CNS damage conditions, which lead to loss of neurological and cognitive functions. We raise the perspective on the steady progress in developing CNS-penetrant P2X7 receptor-specific antagonists that leverage the ATP-P2X7 receptor signaling axis as a potential therapeutic strategy to alleviate traumatic CNS damage and related complications.

Animal Models for the Investigation of P2X7 Receptors

The P2X7 receptor is a trimeric ligand-gated cation channel activated by extracellular adenosine 5'-triphosphate. The study of animals has greatly advanced the investigation of P2X7 and helped to establish the numerous physiological and pathophysiological roles of this receptor in human health and disease. Following a short overview of the P2X7 distribution, roles and functional properties, this article discusses how animal models have contributed to the generation of P2X7-specific antibodies and nanobodies (including biologics), recombinant receptors and radioligands to study P2X7 as well as to the pharmacokinetic testing of P2X7 antagonists. This article then outlines how mouse and rat models have been used to study P2X7. These sections include discussions on preclinical disease models, polymorphic P2X7 variants, P2X7 knockout mice (including bone marrow chimeras and conditional knockouts), P2X7 reporter mice, humanized P2X7 mice and P2X7 knockout rats. Finally, this article reviews the limited number of studies involving guinea pigs, rabbits, monkeys (rhesus macaques), dogs, cats, zebrafish, and other fish species (seabream, ayu sweetfish, rainbow trout and Japanese flounder) to study P2X7.

From lead to clinic: A review of the structural design of P2X7R antagonists

P2X7R, which is a member of the purinergic P2 receptor family, is widely expressed in many immune cells, such as macrophages, lymphocytes, monocytes, and neutrophils. P2X7R is upregulated in response to proinflammatory stimulation, which is closely related to a variety of inflammatory diseases. The inhibition of P2X7 receptors has resulted in the elimination or reduction of symptoms in animal models of arthritis, depression, neuropathic pain, multiple sclerosis, and Alzheimer's disease. Therefore, the development of P2X7R antagonists is of great significance for the treatment of various inflammatory diseases. This review classifies the reported P2X7R antagonists according to their different cores, focuses on the structure-activity relationship (SAR) of the compounds, and analyzes some common substituents and strategies in the design of lead compounds, with the hope of providing valuable information for the development of new and efficient P2X7R antagonists.

Imidazo[1,2-a]Pyridine Derivatives as Novel Dual-Target Inhibitors of ABCB1 and ABCG2 for Reversing Multidrug Resistance

ABCB1 and ABCG2 are the important ATP-binding cassette (ABC) transporters associated with multidrug resistance (MDR). Herein, we designed a series of imidazo[1,2-a]pyridine derivatives as dual-target inhibitors of ABCB1 and ABCG2 through the scaffold hopping strategy. Compound Y22 displayed potential efflux function inhibitory toward both ABCB1 and ABCG2 (reversal fold: ABCB1 = 8.35 and ABCG2 = 2.71) without obvious cytotoxicity. Y22 also enhanced the potency of antiproliferative drugs in vitro. Mechanistic studies demonstrated that Y22 slightly suppressed ATPase activity but did not affect the protein expression of ABCB1 or ABCG2. Notably, Y22 exhibited negligible CYP3A4 inhibition and enhanced the antiproliferative activity of adriamycin in vivo by restoring the sensitivity of resistant cells. Thus, Y22 may be effective clinically in combination with common chemotherapy agents. In summary, Y22 is a potential dual-target inhibitor that reverses MDR by blocking the efflux function of ABCB1 and ABCG2.

P2X receptors: Insights from the study of the domestic dog

Fifty years ago, the late Geoffrey Burnstock described the concept of purinergic nerves and transmission bringing into existence the broader concepts of purinergic signaling including P2X receptors. These receptors are trimeric ligand-gated cation channels activated by extracellular adenosine 5'-triphosphate (ATP). P2X receptors have important roles in health and disease and continue to gain interest as potential therapeutic targets in inflammatory, neurological, cardiovascular and many other disorders including cancer. Current understanding of P2X receptors has largely arisen from the study of these receptors in humans and rodents, but additional insights have been obtained from the study of P2X receptors in the domestic dog, Canis familiaris. This review article will briefly introduce purinergic signaling and P2X receptors, before detailing the pharmacological profiles of the two recombinant canine P2X receptors studied to date, P2X7 and P2X4. The article will then describe the current state of knowledge concerning the distribution and function of the P2X receptor family in dogs. The article will also discuss the characterization of single nucleotide polymorphisms in the canine P2RX7 gene, and contrast this variation to the canine P2RX4 gene, which is largely conserved between dogs. Finally, this article will outline published examples of the use of dogs to study the pharmacokinetics of P2X7 and P2X3 antagonists, and how they have contributed to the preclinical testing of antagonists to human P2X7, CE-224,535, and human P2X3, Gefapixant (AF-219, MK-7264) and Eliapixant (BAY, 1817080), with Gefapixant gaining recent approval for use in the treatment of refractory chronic cough in humans. This article is part of the Special Issue on 'Purinergic Signaling: 50 years'.

Spotlight on P2X7 Receptor PET Imaging: A Bright Target or a Failing Star?

The homotrimeric P2X7 receptor (P2X7R) is expressed by virtually all cells of the innate and adaptive immune system and plays a crucial role in various pathophysiological processes such as autoimmune and neurodegenerative diseases, inflammation, neuropathic pain and cancer. Consequently, the P2X7R is considered a promising target for therapy and diagnosis. As the development of tracers comes hand-in-hand with the development of potent and selective receptor ligands, there is a rising number of PET tracers available in preclinical and clinical studies. This review analyzes the development of P2X7R positron emission tomography (PET) tracers and their potential in various PET imaging applications.

P2X7 receptor as a potential therapeutic target for perinatal brain injury associated with preterm birth

Inflammation-induced preterm birth is the leading cause of perinatal mortality and long-term sequelae in surviving children. IL-1β is a major contributor to inflammation-induced preterm labor and its sequelae. It has recently been demonstrated that the cytokine storm and its progression depend on IL-1β release into circulation and that the P2X7 receptor (P2X7R) is the key player of the ATP-driven NLRP3/caspase-1 activation, necessary for the cleavage of pro-IL-1β to its mature form as well as its subsequent secretion. Being a key component to the inflammatory cascade, P2X7R illuminates a new therapeutic avenue to halt progression of inflammation prior to perinatal brain injury. In this review, we summarize the basic role of the P2X7 receptor in the inflammatory signaling cascade and the possibility of it being used as a therapeutic target in perinatal brain injury. We discuss the antagonists and agonists of the receptor as well as its role in other inflammatory diseases, showing the importance of discovering the functions of the receptor.

Purinergic Receptors of the Central Nervous System: Biology, PET Ligands, and Their Applications

Purinergic receptors play important roles in central nervous system (CNS). These receptors are involved in cellular neuroinflammatory responses that regulate functions of neurons, microglial and astrocytes. Based on their endogenous ligands, purinergic receptors are classified into P1 or adenosine, P2X and P2Y receptors. During brain injury or under pathological conditions, rapid diffusion of extracellular adenosine triphosphate (ATP) or uridine triphosphate (UTP) from the damaged cells, promote microglial activation that result in the changes in expression of several of these receptors in the brain. Imaging of the purinergic receptors with selective Positron Emission Tomography (PET) radioligands has advanced our understanding of the functional roles of some of these receptors in healthy and diseased brains. In this review, we have accumulated a list of currently available PET radioligands of the purinergic receptors that are used to elucidate the receptor functions and participations in CNS disorders. We have also reviewed receptors lacking radiotracer, laying the foundation for future discoveries of novel PET radioligands to reveal these receptors roles in CNS disorders.

P2X7 Receptors in Neurodegeneration: Potential Therapeutic Applications From Basic to Clinical Approaches

Purinergic receptors play important roles in central nervous system (CNS), where the bulk of these receptors are implicated in neuroinflammatory responses and regulation of cellular function of neurons, microglial and astrocytes. Within the P2X receptor family, P2X₇ receptor is generally known for its inactivity in normal conditions and activation by moderately high concentrations (>100 μM) of extracellular adenosine 5′-triphosphate (ATP) released from injured cells as a result of brain injury or pathological conditions. Activation of P2X₇R contributes to the activation and proliferation of microglia and directly contribute to neurodegeneration by provoking microglia-mediated neuronal death, glutamate-mediated excitotoxicity, and NLRP3 inflammasome activation that results in initiation, maturity and release of the pro-inflammatory cytokines and generation of reactive oxygen and nitrogen species. These components of the inflammatory response play important roles in many neural pathologies and neurodegeneration disorders. In CNS, expression of P2X₇R on microglia, astrocytes, and oligodendrocytes are upregulated under neuroinflammatory conditions. Several in vivo studies have demonstrated beneficial effects of the P2X₇ receptor antagonists in animal model systems of neurodegenerative diseases. A number of specific and selective P2X₇ receptor antagonists have been developed, but only few of them have shown efficient brain permeability. Finding potent and selective P2X₇ receptor inhibitors which are also CNS penetrable and display acceptable pharmacokinetics (PK) has presented challenges for both academic researchers and pharmaceutical companies. In this review, we discuss the role of P2X₇ receptor function in neurodegenerative diseases, the pharmacological inhibition of the receptor, and PET radiopharmaceuticals which permit non-invasive monitoring of the P2X₇ receptor contribution to neuroinflammation associated with neurodegeneration.

Synthesis and Characterization of the Novel Rodent-Active and CNS-Penetrant P2X7 Receptor Antagonist Lu AF27139

There remains an insufficient number of P2X7 receptor antagonists with adequate rodent potency, CNS permeability, and pharmacokinetic properties from which to evaluate CNS disease hypotheses preclinically. Herein, we describe the molecular pharmacology, safety, pharmacokinetics, and functional CNS target engagement of Lu AF27139, a novel rodent-active and CNS-penetrant P2X7 receptor antagonist. Lu AF27139 is highly selective and potent against rat, mouse, and human forms of the receptors. The rat pharmacokinetic profile is favorable with high oral bioavailability, modest clearance (0.79 L/(h kg)), and good CNS permeability. In vivo mouse CNS microdialysis studies of lipopolysaccharide (LPS)-primed and 2'(3')-O-(benzoylbenzoyl)adenosine-5'-triphosphate (BzATP)-induced IL-1β release demonstrate functional CNS target engagement. Importantly, Lu AF27139 was without effect in standard in vitro and in vivo toxicity studies. Based on these properties, we believe Lu AF27139 will be a valuable tool for probing the role of the P2X7 receptor in rodent models of CNS diseases.

Design, Synthesis, and Preclinical Evaluation of 3-Methyl-6-(5-thiophenyl)-1,3-dihydro-imidazo[4,5-b]pyridin-2-ones as Selective GluN2B Negative Allosteric Modulators for the Treatment of Mood Disorders

Selective inhibitors of the GluN2B subunit of N-methyl-d-aspartate receptors in the ionotropic glutamate receptor superfamily have been targeted for the treatment of mood disorders. We sought to identify structurally novel, brain penetrant, GluN2B-selective inhibitors suitable for evaluation in a clinical setting in patients with major depressive disorder. We identified a new class of negative allosteric modulators of GluN2B that contain a 1,3-dihydro-imidazo[4,5-b]pyridin-2-one core. This series of compounds had poor solubility properties and poor permeability, which was addressed utilizing two approaches. First, a series of structural modifications was conducted which included replacing hydrogen bond donor groups. Second, enabling formulation development was undertaken in which a stable nanosuspension was identified for lead compound 12. Compound 12 was found to have robust target engagement in rat with an ED₇₀ of 1.4 mg/kg. The nanosuspension enabled sufficient margins in preclinical toleration studies to nominate 12 for progression into advanced good laboratory practice studies.

The P2X7 Receptor: Central Hub of Brain Diseases

The P2X7 receptor is a cation channel activated by high concentrations of adenosine triphosphate (ATP). Upon long-term activation, it complexes with membrane proteins forming a wide pore that leads to cell death and increased release of ATP into the extracellular milieu. The P2X7 receptor is widely expressed in the CNS, such as frontal cortex, hippocampus, amygdala and striatum, regions involved in neurodegenerative diseases and psychiatric disorders. Despite P2X7 receptor functions in glial cells have been extensively studied, the existence and roles of this receptor in neurons are still controversially discussed. Regardless, P2X7 receptors mediate several processes observed in neuropsychiatric disorders and brain tumors, such as activation of neuroinflammatory response, stimulation of glutamate release and neuroplasticity impairment. Moreover, P2X7 receptor gene polymorphisms have been associated to depression, and isoforms of P2X7 receptors are implicated in neuropsychiatric diseases. In view of that, the P2X7 receptor has been proposed to be a potential target for therapeutic intervention in brain diseases. This review discusses the molecular mechanisms underlying P2X7 receptor-mediated signaling in neurodegenerative diseases, psychiatric disorders, and brain tumors. In addition, it highlights the recent advances in the development of P2X7 receptor antagonists that are able of penetrating the central nervous system.

The purinergic P2X7 receptor as a potential drug target to combat neuroinflammation in neurodegenerative diseases

Neurodegenerative diseases (NDDs) represent a huge social burden, particularly in Alzheimer's disease (AD) in which all proposed treatments investigated in murine models have failed during clinical trials (CTs). Thus, novel therapeutic strategies remain crucial. Neuroinflammation is a common pathogenic feature of NDDs. As purinergic P2X7 receptors (P2X7Rs) are gatekeepers of inflammation, they could be developed as drug targets for NDDs. Herein, we review this challenging hypothesis and comment on the numerous studies that have investigated P2X7Rs, emphasizing their molecular structure and functions, as well as their role in inflammation. Then, we elaborate on research undertaken in the field of medicinal chemistry to determine potential P2X7R antagonists. Subsequently, we review the state of neuroinflammation and P2X7R expression in the brain, in animal models and patients suffering from AD, Parkinson's disease, amyotrophic lateral sclerosis, Huntington's disease, multiple sclerosis, and retinal degeneration. Next, we summarize the in vivo studies testing the hypothesis that by mitigating neuroinflammation, P2X7R blockers afford neuroprotection, increasing neuroplasticity and neuronal repair in animal models of NDDs. Finally, we reviewed previous and ongoing CTs investigating compounds directed toward targets associated with NDDs; we propose that CTs with P2X7R antagonists should be initiated. Despite the high expectations for putative P2X7Rs antagonists in various central nervous system diseases, the field is moving forward at a relatively slow pace, presumably due to the complexity of P2X7Rs. A better pharmacological approach to combat NDDs would be a dual strategy, combining P2X7R antagonism with drugs targeting a selective pathway in a given NDD.

P2X7 in Cancer: From Molecular Mechanisms to Therapeutics

P2X7 is a transmembrane receptor expressed in multiple cell types including neurons, dendritic cells, macrophages, monocytes, B and T cells where it can drive a wide range of physiological responses from pain transduction to immune response. Upon activation by its main ligand, extracellular ATP, P2X7 can form a nonselective channel for cations to enter the cell. Prolonged activation of P2X7, via high levels of extracellular ATP over an extended time period can lead to the formation of a macropore, leading to depolarization of the plasma membrane and ultimately to cell death. Thus, dependent on its activation state, P2X7 can either drive cell survival and proliferation, or induce cell death. In cancer, P2X7 has been shown to have a broad range of functions, including playing key roles in the development and spread of tumor cells. It is therefore unsurprising that P2X7 has been reported to be upregulated in several malignancies. Critically, ATP is present at high extracellular concentrations in the tumor microenvironment (TME) compared to levels observed in normal tissues. These high levels of ATP should present a survival challenge for cancer cells, potentially leading to constitutive receptor activation, prolonged macropore formation and ultimately to cell death. Therefore, to deliver the proven advantages for P2X7 in driving tumor survival and metastatic potential, the P2X7 macropore must be tightly controlled while retaining other functions. Studies have shown that commonly expressed P2X7 splice variants, distinct SNPs and post-translational receptor modifications can impair the capacity of P2X7 to open the macropore. These receptor modifications and potentially others may ultimately protect cancer cells from the negative consequences associated with constitutive activation of P2X7. Significantly, the effects of both P2X7 agonists and antagonists in preclinical tumor models of cancer demonstrate the potential for agents modifying P2X7 function, to provide innovative cancer therapies. This review summarizes recent advances in understanding of the structure and functions of P2X7 and how these impact P2X7 roles in cancer progression. We also review potential therapeutic approaches directed against P2X7.

P2X7 receptor antagonists for the treatment of systemic inflammatory disorders

P2X7 has continued to be a target of immense interest since it is implicated in several peripheral and central nervous system disorders that result from inflammation. This review primarily describes new P2X7 receptor antagonists that have been investigated and disclosed in patent applications or primary literature since 2015. While a crystal structure of the receptor to aid in the design of novel chemical structures remains elusive, many of the chemotypes that have been disclosed contain similarities, with an amide motif present in all series that have been explored to date. Several of the recent antagonists described are brain penetrant, and two compounds are currently in clinical trials for CNS indications. Additionally, brain penetrant PET ligands have been developed that aid in measuring target engagement and these ligands can potentially be used as biomarkers.

The first radiosynthesis of 2-amino-5-[18F]fluoropyridines via a "minimalist" radiofluorination/palladium-catalyzed amination sequence from anisyl(2-bromopyridinyl)iodonium triflate

The synthesis of 2-amino-5-[¹⁸F]fluoropyridines was achieved in 8-85% yields by palladium-catalyzed reaction of 2-bromo-5-[¹⁸F]fluoropyridine with piperidine, dimethylamine, butylamine, methylpiperazine, benzylamine, aniline and 3-aminopyridine. 2-Bromo-5-[¹⁸F]fluoropyridine was obtained by radiofluorination of anisyl(2-bromopyridinyl-5)iodonium triflate (88% yield). The radiofluorination step was performed under "minimalist" conditions to guarantee a successful subsequent amination reaction.

Synthesis, Biological Evaluation, and Molecular Modeling Studies of New Thiadiazole Derivatives as Potent P2X7 Receptor Inhibitors

Twenty new 2-(1H-pyrazol-1-yl)-1,3,4-thiadiazole analogs were synthetized to develop P2X7 receptor (P2X7R) inhibitors. P2X7R inhibition in vitro was evaluated in mouse peritoneal macrophages, HEK-293 cells transfected with hP2X7R (dye uptake assay), and THP-1 cells (IL-1β release assay). The 1-(5-phenyl-1,3,4-thiadiazol-2-yl)-1H-pyrazol-5-amine derivatives 9b, 9c, and 9f, and 2-(3,5-dimethyl-1H-pyrazol-1-yl)-5-(4-fluorophenyl)-1,3,4-thiadiazole (11c) showed inhibitory effects with IC₅₀ values ranging from 16 to 122 nM for reduced P2X7R-mediated dye uptake and 20 to 300 nM for IL-1β release. In addition, the in vitro ADMET profile of the four most potent derivatives was determined to be in acceptable ranges concerning metabolic stability and cytotoxicity. Molecular docking and molecular dynamics simulation studies of the molecular complexes human P2X7R/9f and murine P2X7R/9f indicated the putative intermolecular interactions. Compound 9f showed affinity mainly for the Arg268, Lys377, and Asn266 residues. These results suggest that 2-(1H-pyrazol-1-yl)-1,3,4-thiadiazole analogs may be promising novel P2X7R inhibitors with therapeutic potential.

ATP-activated P2X7 receptor in the pathophysiology of mood disorders and as an emerging target for the development of novel antidepressant therapeutics

Mood disorders are a group of psychiatric conditions that represent leading global disease burdens. Increasing evidence from clinical and preclinical studies supports that innate immune system dysfunction plays an important part in the pathophysiology of mood disorders. P2X7 receptor, belonging to the ligand-gated ion channel P2X subfamily of purinergic P2 receptors for extracellular ATP, is highly expressed in immune cells including microglia in the central nervous system (CNS) and has a vital role in mediating innate immune response. The P2X7 receptor is also important in neuron-glia signalling in the CNS. The gene encoding human P2X7 receptor is located in a locus of susceptibility to mood disorders. In this review, we will discuss the recent progress in understanding the role of the P2X7 receptor in the pathogenesis and development of mood disorders and in discovering CNS-penetrable P2X7 antagonists for potential uses in in vivo imaging to monitor brain inflammation and antidepressant therapeutics.

Recent Advances in CNS P2X7 Physiology and Pharmacology: Focus on Neuropsychiatric Disorders

The ATP-gated P2X7 ion channel is an abundant microglial protein in the CNS that plays an important pathological role in executing ATP-driven danger signal transduction. Emerging data has generated scientific interest and excitement around targeting the P2X7 ion channel as a potential drug target for CNS disorders. Over the past years, a wealth of data has been published on CNS P2X7 biology, in particular the role of P2X7 in microglial cells, and in vivo effects of brain-penetrant P2X7 antagonists. Likewise, significant progress has been made around the medicinal chemistry of CNS P2X7 ligands, as antagonists for in vivo target validation in models of CNS diseases, to identification of two clinical compounds (JNJ-54175446 and JNJ-55308942) and finally, discovery of P2X7 PET ligands. This review is an attempt to bring together the current understanding of P2X7 in the CNS with a focus on P2X7 as a drug target in neuropsychiatric disorders.

The P2X7 purinergic receptor: An emerging therapeutic target in cardiovascular diseases

The P2X7 purinergic receptor, a calcium permeable cationic channel, is activated by extracellular ATP. Most studies show that P2X7 receptor plays an important role in the nervous system diseases, immune response, osteoporosis and cancer. Mounting evidence indicates that P2X7 receptor is also associated with cardiovascular disease. For example, the P2X7 receptor activated by ATP can attenuate myocardial ischemia-reperfusion injury. By contrast, inhibition of P2X7 receptor decreases arrhythmia after myocardial infarction, prolongs cardiac survival after a long term heart transplant, alleviates the dilated cardiomyopathy and the autoimmune myocarditis process. The P2X7 receptor also mitigates vascular diseases including atherosclerosis, hypertension, thrombosis and diabetic retinopathy. This review focuses on the latest research on the role and therapeutic potential of P2X7 receptor in cardiovascular diseases.

The P2X7 receptor: A main player in inflammation

Damage associated molecular patterns (DAMPs) are intracellular molecules released from infected or injured cells to activate inflammatory and reparatory responses. One of the most ancient and conserved DAMPs is extracellular ATP that exerts its phlogistic activity mainly through activation of the P2X7 receptor (P2X7R). The P2X7R is an ATP gated ion channel, expressed by most immune cells, including the monocyte-derived cell lineages, T and B lymphocytes and their precursors. Here we give an overview of recent and established literature on the role of P2X7R in septic and sterile inflammation. P2X7R ability in restraining intracellular bacteria and parasite infection by modulation of the immune response are described, with particular focus on Mycobacteria and Plasmodium. Emerging literature on the role of P2X7 in viral infections such as HIV-1 is also briefly covered. Finally, we describe the numerous intracellular pathways related to inflammation and activated by the P2X7R, including the NLRP3 inflammasome, NF-kB, NFAT, GSK3β and VEGF, and discuss the involvement of P2X7R in chronic diseases. The possible therapeutic applications of P2X7R antagonists are also described.

4-Methyl-6,7-dihydro-4H-triazolo[4,5-c]pyridine-Based P2X7 Receptor Antagonists: Optimization of Pharmacokinetic Properties Leading to the Identification of a Clinical Candidate

The synthesis and preclinical characterization of novel 4-(R)-methyl-6,7-dihydro-4H-triazolo[4,5-c]pyridines that are potent and selective brain penetrant P2X7 antagonists are described. Optimization efforts based on previously disclosed unsubstituted 6,7-dihydro-4H-triazolo[4,5-c]pyridines, methyl substituted 5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazines, and several other series lead to the identification of a series of 4-(R)-methyl-6,7-dihydro-4H-triazolo[4,5-c]pyridines that are selective P2X7 antagonists with potency at the rodent and human P2X7 ion channels. These novel P2X7 antagonists have suitable physicochemical properties, and several analogs have an excellent pharmacokinetic profile, good partitioning into the CNS and show robust in vivo target engagement after oral dosing. Improvements in metabolic stability led to the identification of JNJ-54175446 (14) as a candidate for clinical development. The drug discovery efforts and strategies that resulted in the identification of the clinical candidate are described herein.