Synthesis and Structure-Activity Relationship Studies of Benzimidazole-4,7-dione-Based P2X3 Receptor Antagonists as Novel Anti-Nociceptive Agents.

Jinsu Bae,Myung-Ha Yoon,Xuehao Han,Yong-Chul Kim,Woong-Mo Kim,Yeo-Ok Kim

doi:10.3390/molecules27041337

Abstract

P2X3 receptors (P2X3R) are ATP-gated ion channels predominantly expressed in C- and Aδ-fiber primary afferent neurons and have been introduced as a novel therapeutic target for neurological disorders, including neuropathic pain and chronic cough. Because of its localized distribution, antagonism of P2X3R has been thoroughly considered, and the avoidance of issues related to CNS side effects has been proven in clinical trials. In this article, benzimidazole-4,7-dione-based derivatives were introduced as a new chemical entity for the development of P2X3R antagonists. Starting from the discovery of a hit compound from the screening of 8364 random library compounds in the Korea Chemical Bank, which had an IC50 value of 1030 nM, studies of structure–activity and structure–property relationships enabled further optimization toward improving the antagonistic activities as well as the drug’s physicochemical properties, including metabolic stability. As for the results, the final optimized compound 14h was developed with an IC50 value of 375 nM at P2X3R with more than 23-fold selectivity versus P2X2/3R, along with properties of metabolic stability and improved solubility. In neuropathic pain animal models evoked by either nerve ligation or chemotherapeutics in male Sprague-Dawley rats, compound 14h showed anti-nociceptive effects through an increase in the mechanical withdrawal threshold as measured by von Frey filament following intravenous administration.

Highlights

P2X receptors (P2XR) are reported to function as ligand-gated cation channels that are activated by the binding of extracellular adenosine 5 -triphosphate (ATP) [1,2] to induce the influx of cations, e.g., calcium, potassium, and sodium ions, within milliseconds, which triggers neuronal responses via the depolarization of cell membranes [3,4,5]
LFiborrartyheScerveeanluinagt:ioDnisocofvPe2ryXoRf NacetwivSitciaefsf,olad cfoerllh-bPa2sXe3dRaescseapytorsyAsntetamgowniasst employed to measure the level of fluorescence emission, based on Fluo-4 dye, during Ca2+ influx evoked by αβmeATP in HEK293 cells stably expressing hP2X2/3R and hP2X3R
For the evaluation of P2XR activities, a cell-based assay system was employed to measure the level of fluorescence emission, based on Fluo-4 dye, during Ca2+ influx evoked by αβmeATP in HEK293 cells stably expressing hP2X2/3R and hP2X3R

Summary

Introduction

P2X receptors (P2XR) are reported to function as ligand-gated cation channels that are activated by the binding of extracellular adenosine 5 -triphosphate (ATP) [1,2] to induce the influx of cations, e.g., calcium, potassium, and sodium ions, within milliseconds, which triggers neuronal responses via the depolarization of cell membranes [3,4,5]. Among the P2X receptor subtypes, P2X3 receptors (P2X3R) are expressed as homomeric P2X3 or heteromeric P2X2/3 trimers predominantly in small-tomedium-diameter C- and Aδ-fibers of primary afferent neurons, which suggests that these receptors could serve as therapeutic targets that are highly specific to the pain sensing systems and allow the avoidance of CNS-related side effects [8,9]. Molecules 2022, 27, 1337 in small-to-medium-diameter C- and Aδ-fibers of primary afferent neurons, which2soufg15gests that these receptors could serve as therapeutic targets that are highly specific to the pain sensing systems and allow the avoidance of CNS-related side effects [8,9]. Potent and selective P2X3 receptor antagonists have been developed by pphhaarrmmaacceeuuttiiccaall iinndduussttrriieess aanndd aaccaaddeemmiicc iinnssttiittuutteess. TThhuuss,, sseevveerraall pphhaarrmmaacceeuuttiiccaall iinndduussttrriieess,, ee..gg..,, BBeelllluuss,, SShhiioonnooggii,, aanndd BBaayyeerr,, hhaavvee ddeevveellooppeedd aannttaaggoonniissttss tthhaatt aarree mmoorree sseelleeccttiivvee ffoorr PP22XX33 rreecceeppttoorr oovveerr PP22XX22//33 rreecceeppttoorrss,, ssuucchh aass BBLLUU--55993377 ((44)),, SSiivvooppiixxaanntt ((55)),, aannddEElliiaappiixxaanntt((66))..TThhoosseeddeerrivivaatitviveesshhaavveebbeeeneninivnevsetsigtiagtaetdedininclicnliincaiclatlritarlisafolsr fcohrrochnriconcoicucgohutgrheattrmeaetnmt.ent

Methods

Results

Conclusion