N-substituted phenoxazine and acridone derivatives: structure-activity relationships of potent P2X4 receptor antagonists

J Med Chem. 2012 Nov 26;55(22):9576-88. doi: 10.1021/jm300845v. Epub 2012 Nov 1.


P2X4 receptor antagonists have potential as drugs for the treatment of neuropathic pain and neurodegenerative diseases. In the present study the discovery of phenoxazine derivatives as potent P2X4 antagonists is described. N-Substituted phenoxazine and related acridone and benzoxazine derivatives were synthesized and optimized with regard to their potency to inhibit ATP-induced calcium influx in 1321N1 astrocytoma cells stably transfected with the human P2X4 receptor. In addition, species selectivity (rat, mouse, human) and receptor subtype selectivity (versus P2X1,2,3,7) were investigated. The most potent P2X4 antagonist of the present series was N-(benzyloxycarbonyl)phenoxazine (26, PSB-12054) with an IC(50) of 0.189 μM and good selectivity versus the other human P2X receptor subtypes. N-(p-Methylphenylsulfonyl)phenoxazine (21, PSB-12062) was identified as a selective P2X4 antagonist that was equally potent in all three species (IC(50): 0.928-1.76 μM). The compounds showed an allosteric mechanism of action. The present study represents the first structure-activity relationship analysis of P2X4 antagonists.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acridines / chemistry*
  • Acridones
  • Adenosine Triphosphate / metabolism
  • Animals
  • Astrocytoma / drug therapy
  • Astrocytoma / metabolism
  • Brain Neoplasms / drug therapy
  • Brain Neoplasms / metabolism
  • CHO Cells
  • Calcium / metabolism
  • Cells, Cultured
  • Cricetinae
  • Humans
  • Mice
  • Molecular Structure
  • Oxazines / chemistry*
  • Oxazines / pharmacology*
  • Purinergic P2 Receptor Antagonists / chemistry
  • Purinergic P2 Receptor Antagonists / pharmacology*
  • Radioligand Assay
  • Rats
  • Receptors, Purinergic P2X4 / chemistry*
  • Receptors, Purinergic P2X4 / metabolism
  • Species Specificity
  • Structure-Activity Relationship
  • Sulfonamides / chemistry
  • Sulfonamides / pharmacology*


  • Acridines
  • Acridones
  • N-(benzyloxycarbonyl)phenoxazine
  • N-(p-methylphenylsulfonyl)phenoxazine
  • Oxazines
  • Purinergic P2 Receptor Antagonists
  • Receptors, Purinergic P2X4
  • Sulfonamides
  • acridone
  • Adenosine Triphosphate
  • phenoxazine
  • Calcium