YM-90709 is a competitive antagonist of the interleukin-5 (IL-5) receptor that has IC50 values of 1 and 0.57 μM for peripheral human eosinophils and eosinophilic HL-60 clone 15 cells, respectively, in a radioligand binding assay. It inhibits IL-5-induced eosinophil survival (IC50 = 0.45 μM) and JAK2 phosphorylation in vitro. YM-90709 inhibits eosinophil and lymphocyte infiltration (ED50s = 0.32 and 0.12 mg/kg, respectively) into the brochoalveolar lavage fluid (BALF) of rats and eosinophil infiltration (ED50 = 0.05 mg/kg) into the BALF of mice in models of airway inflammation.
