High affinity P2X3 receptor antagonist (Ki values are 36, 82 and 4144 nM for P2X3, P2X1 and P2X2 recombinant receptors respectively). Shows no activity at P2Y1, P2Y2 and P2Y11 receptors (IC50 > 10 μM). Potently inhibits α,β-meATP-evoked desensitizing currents in rat DRG neurons (IC50 = 527 nM). Shows antitumor activity against several tumor types.