Structure–activity relationship studies of pyrimidine-2,4-dione derivatives as potent P2X7 receptor antagonists

Unlocking the therapeutic potential of P2X7 receptor: a comprehensive review of its role in neurodegenerative disorders

The P2X7 receptor (P2X7R), an ATP-gated ion channel, has emerged as a crucial player in neuroinflammation and a promising therapeutic target for neurodegenerative disorders. This review explores the current understanding of P2X7R's structure, activation, and physiological roles, focusing on its expression and function in microglial cells. The article examines the receptor's involvement in calcium signaling, microglial activation, and polarization, as well as its role in the pathogenesis of Alzheimer's disease, Parkinson's disease, multiple sclerosis, and amyotrophic lateral sclerosis. The review highlights the complex nature of P2X7R signaling, discussing its potential neuroprotective and neurotoxic effects depending on the disease stage and context. It also addresses the development of P2X7R antagonists and their progress in clinical trials, identifying key research gaps and future perspectives for P2X7R-targeted therapy development. By providing a comprehensive overview of the current state of knowledge and future directions, this review serves as a valuable resource for researchers and clinicians interested in exploring the therapeutic potential of targeting P2X7R for the treatment of neurodegenerative disorders.

Identification of novel P2X7R antagonists by using structure-based virtual screening and cell-based assays

In the tumor microenvironment, inflammation and necrosis cause the accumulations of ATP extracellularly, and high concentrations of ATP can activate P2X7 receptors (P2X7R), which leads to the influx of Na⁺ , K⁺ , or Ca²⁺ into cells and trigger the downstream signaling pathways. P2X7R is a relatively unique ligand-gated ion channel, which is over-expressed in most tumor cells. The activated P2X7R facilitates the tumor growth, invasion, and metastasis. Inhibition of the P2X7R activation can be applied as a potential anti-tumor therapy strategy. There are currently no anti-tumor agents against P2X7R, though several P2X7R antagonists for indications such as anti-inflammatory and anti-depression were reported. In this study, we combined homology modeling (HM), virtual screening, and EB intake assay to characterize the structural features of P2X7R and identify several novel antagonists, which were chemically different from any other known P2X7R antagonists. The identified antagonists could effectively prevent the pore opening of P2X7R with IC50 values ranging from 29.14 to 35.34 μM. HM model showed the area between ATP-binding pocket, and allosteric sides were hydrophobic and suitable for small molecule interaction. Molecular docking indicated a universal binding mode, of which residues R294 and K311 were used as hydrogen bond donors to participate in antagonist interactions. The binding mode can potentially be utilized for inhibitor optimization for increased affinity, and the identified antagonists can be further tested for anti-cancer activity or may serve as chemical agents to study P2X7R related functions.

Synthesis and Pharmacological Evaluation of Novel Non-nucleotide Purine Derivatives as P2X7 Antagonists for the Treatment of Neuroinflammation

The ATP-gated P2X7 purinergic receptor (P2X7) is involved in the pathogenesis of many neurodegenerative diseases (NDDs). Several P2X7 antagonists have been developed, though none of them reached clinical trials for this indication. In this work, we designed and synthesized novel blood-brain barrier (BBB)-permeable derivatives as potential P2X7 antagonists. They comprise purine or xanthine cores linked to an aryl group through different short spacers. Compounds were tested in YO-PRO-1 uptake assays and intracellular calcium dynamics in a human P2X7-expressing HEK293 cell line, two-electrode voltage-clamp recordings in Xenopus laevis oocytes, and in interleukin 1β release assays in mouse peritoneal macrophages. BBB permeability was assessed by parallel artificial membrane permeability assays and P-glycoprotein ATPase activity. Dichloroarylpurinylethanones featured a certain P2X7 blockade, being compound 6 (2-(6-chloro-9H-purin-9-yl)-1-(2,4-dichlorophenyl)ethan-1-one), named ITH15004, the most potent, selective, and BBB-permeable antagonist. Compound 6 can be considered as a first non-nucleotide purine hit for future drug optimizations.

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.

Access to 1,3-oxazine-2,4-diones/1,3-thiazine-2,4-diones via organocatalytic CO2/COS incorporation into allenamides

Organocatalyzed [4 + 2] annulation of CO₂/COS with allenamides is firstly reported to synthesize 1,3-oxazine-2,4-diones and 1,3-thiazine-2,4-diones in moderate to excellent yields under mild reaction conditions. The catalytic potential of a series of Lewis base CO₂ and COS adducts are particularly noted for this process, which features high regio- and chemo-selectivity, step-economy, facile scalability, and easy product derivatization. This study offers the potential for the application of organocatalytic systems for CO₂ and COS chemical transformation.

Potent Suppressive Effects of 1-Piperidinylimidazole Based Novel P2X7 Receptor Antagonists on Cancer Cell Migration and Invasion

The P2X7 receptor (P2X7R) has been reported as a key mediator in inflammatory processes and cancer invasion/metastasis. In this study, we report the discovery of novel P2X7R antagonists and their functional activities as potential antimetastatic agents. Modifications of the hydantoin core-skeleton and the side chain substituents of the P2X7R antagonist 7 were performed. The structure-activity relationships (SAR) and optimization demonstrated the importance of the sulfonyl group at the R1 position and the substituted position and overall size of R2 for P2X7R antagonism. The optimized novel analogues displayed potent P2X7 receptor antagonism (IC50 = 0.11-112 nM) along with significant suppressive effects on IL-1β release (IC50 = 0.32-210 nM). Moreover, representative antagonists (12g, 13k, and 17d) with imidazole and uracil core skeletons significantly inhibited the invasion of MDA-MB-231 triple negative breast cancer cells and cancer cell migration in a zebrafish xenograft model, suggesting the potential therapeutic application of these novel P2X7 antagonists to block metastatic cancer.

The evolution of P2X7 antagonists with a focus on CNS indications

The P2X7 receptor is an ATP-gated nonselective cation channel that has been linked to a number of inflammatory diseases. Activation of the P2X7 receptor by elevated levels of ATP results in the release of proinflammatory cytokines and elevated levels of these cytokines has been associated with a variety of disease states. A number of research groups in both industry and academia have explored the identification of P2X7R antagonists as therapeutic agents. Much of this early effort focused on the treatment of diseases related to peripheral inflammation and resulted in several clinical candidates, none of which were advanced to market. The emerging role of the P2X7 receptor in neuroinflammation and related diseases has resulted in a shift in medicinal chemistry efforts toward the development of centrally penetrant antagonists. This review will highlight the biology supporting the role of P2X7 in diseases related to neuroinflammation and review the recent medicinal chemistry efforts to identify centrally penetrant antagonists.