In Vitro: Ro-51 has highly selective for P2X 3 and P2X 2/3 exhibiting no antagonistic activity at other P2X receptor family members tested (P2X 1 , P2X 2 , P2X 4 , P2X 5 , and P2X 7 ) at concentrations up to 10 μM. RO51 also shows a significant drop in potency on human P2X3 receptors (IC50 = 110.5 and 0.04 nM, respectively for human and rat P2X3).
In Vivo: Ro-51 suffers rapid clearance, short half-lives, and high protein binding in rat.