A CRTH2/DP2 antagonist (IC50s = 9.58, 14, 15.5, and 7.6 nM for recombinant human, rat, mouse, and guinea pig CRTH2/DP2 receptors, respectively); selective for CRTH2/DP2 over a panel of 65 enzymes, ion channels, and transporters with 2-induced shape change of eosinophils (IC50s = 2 and 8.2 nM in isolated eosinophils and whole blood, respectively) and eosinophil chemotaxis (IC50 = 1.3 nM); reduces PGD2-induced systemic eosinophilia in guinea pigs (ID50 = 131 μg/kg)