In vitro activity: A-317491 does not undergo any detectable metabolism (oxidation or glucuronidation) in in vitro assays using human and rat liver microsomes. It potently 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 neurotransmitter receptors, ion channels, and enzymes.

Kinase Assay: A-317491 is a selective non-nucleotide antagonist of P2X3 and P2X2/3 receptors, which inhibits calcium flux mediated by the receptors. The purinergic P2X3 and P2X2/3 receptors are in the peripheral nervous system almost exclusively confined to afferent sensory neurons, where they are found both at peripheral and central synapses. The P2X3 receptor is implicated in both neuropathic and inflammatory pain. It is known that P2X3 and P2X2/3 receptors stimulate the pronociceptive effects of ATP upon activation. Studies indicate that the P2X3 receptor is implicated in both neuropathic and inflammatory pain. P2X3 receptor is a promising target for therapeutic intervention in cancer patients for pain management.

Cell Assay: