LAS191859 is a CRTH2/DP2 antagonist with IC50 values of 9.58, 14, 15.5, and 7.6 nM for recombinant human, rat, mouse, and guinea pig CRTH2/DP2 receptors, respectively. In vitro evidence in GTPγS binding studies indicate that LAS191859 is a CRTh2 antagonist with activity in the low nanomolar range. This potency is also maintained in cellular assays performed with human eosinophils and whole blood. The main differentiation of LAS191859 vs other CRTh2 antagonists is in its receptor binding kinetics. LAS191859 has a residence time half-life of 21h at CRTh2 that translates into a long-lasting in vivo efficacy that is independent of plasma levels
