YM-341619 (AS1617612) is a potent and orally active STAT6 inhibitor with an IC50 of 0.70 nM. YM-341619 inhibits Th2 differentiation in mouse spleen T cells induced by IL-4 (IC50=0.28 nM) without affecting Th1 cell differentiation. YM-341619 is a promising compound for the the research of allergic diseases, such as allergic asthma[2].In Vitro: YM-341619 (0.1-100 nM; pretreatment 30 min before IL-4) inhibits IL-4-increased STAT6 luciferase gene activity in a concentration dependent manner, exhibiting an IC50 value of 1.5 nM in FW4 cells[2].YM-341619 (0.1-10 nM; pretreatment 30 min before IL-4) concentration-dependently decreases the production of IL-4 and the expression of GATA-3 mRNA in T cells cultured with IL-4. And it has no effects on the production of IFN-γ or the expression of T-bet (a Th1 transcription factor) mRNA in T cells cultured with IL-12[2].In Vivo: YM-341619 (intravenous?injection; 1 mg/kg) exhibits CLtot, t1/2, Vd values of 36.1 mL/min/kg, 1.0 hour, 3117 mL/kg, respectively. And it exhibits Cmax, Tmax, AUC, and F% values of 80 ng/mL, 0.5h, 114 ng h/mL and 25%, respectively in 8-week-old female balb/c mice.YM-341619 (oral administration; 0.003-0.03 mg/kg) suppresses the IgE level in a dose-dependent manner, but not the IgG2a level, and the ED50 value of YM-341619 for the suppression of IgE production is 0.026 mg/kg. YM-341619 tends to decrease IL-4 production and decrease IL-13 production in a dose-dependent manner (both 57%), but does not affect IFN-γ production in DNP-Ascaris-sensitized rats[2].