Discovery of Triazolopyrimidine Derivatives as Selective P2X3 Receptor Antagonists Binding to an Unprecedented Allosteric Site as Evidenced by Cryo-Electron Microscopy

  • J Med Chem. 2024 Aug 5. doi: 10.1021/acs.jmedchem.4c01214.
Ga-Ram Kim  1 ,  Subin Kim  1 ,  Yeo-Ok Kim  2 ,  Xuehao Han  2 ,  Jessica Nagel  3 ,  Jihyun Kim  1 ,  Dahin Irene Song  4 ,  Christa E Müller  3 ,  Myung-Ha Yoon  2 ,  Mi Sun Jin  1 ,  Yong-Chul Kim  1
Affiliations
  • 1. School of Life Sciences, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.
  • 2. Department of Anesthesiology and Pain Medicine, Chonnam National University Medical School, 42 Jebong-ro, Dong-gu, Gwangju 61469, Republic of Korea.
  • 3. PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical & Medicinal Chemistry, University of Bonn, An der Immenburg 4, Bonn 53113, Germany.
  • 4. Bioengineering, University of Pennsylvania, 3451 Walnut St, Philadelphia, Pennsylvania 19104, United States.
PMID: 39102524 DOI: 10.1021/acs.jmedchem.4c01214
Abstract

The P2X3 Receptor (P2X3R), an ATP-gated cation channel predominantly expressed in C- and Aδ-primary afferent neurons, has been proposed as a drug target for neurological inflammatory diseases, e.g., neuropathic pain, and chronic cough. Aiming to develop novel, selective P2X3R antagonists, tetrazolopyrimidine-based hit compound 9 was optimized through structure-activity relationship studies by modifying the tetrazole core as well as side chain substituents. The optimized antagonist 26a, featuring a cyclopropane-substituted triazolopyrimidine core, displayed potent P2X3R-antagonistic activity (IC50 = 54.9 nM), 20-fold selectivity versus the heteromeric P2X2/3R, and high selectivity versus Other P2XR subtypes. Noncompetitive P2X3R blockade was experimentally confirmed by calcium influx assays. Cryo-electron microscopy revealed that 26a stabilizes the P2X3R in its desensitized state, acting as a molecular barrier to prevent ions from accessing the central pore. In vivo studies in a rat neuropathic pain model (spinal nerve ligation) showed dose-dependent antiallodynic effects of 26a, thus presenting a novel, promising lead structure.

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