A-317491 (ABT 202) is a non-nucleotide P2X3 ( Ki: 22 nM) and P2X2/3 receptor (Ki: 9 nM) antagonist, which inhibits calcium flux mediated by the receptors.

P2X2:9 nM (Ki, cell free), P2X3:22 nM(Ki, cell free)

A-317491 blocks recombinant human and rat P2X3 and P2X2/3 receptor-mediated calcium flux (Ki = 22-92 nM) and is highly selective (IC50 >10 μM) over other P2 receptors and other ion channels, neurotransmitter receptors, and enzymes [1].

A-317491 dose-dependently reduces complete Freund's adjuvant-induced thermal hyperalgesia in the rat (ED50: 30 μmol/kg s.c.). A-317491 is most potent in attenuating both thermal hyperalgesia and mechanical allodynia after chronic nerve constriction injury (ED50: 10-15 μmol/kg s.c.). Although active in chronic pain models, A-317491 is ineffective in reducing nociception in animal models of acute pain, postoperative pain, and visceral pain (ED50 >100 μmol/kg s.c.) [1]. A-317491 is effective in reducing pain associated behavior in several animal models of inflammatory and neuropathic pain when administered systemically [2].