AS1517499 is a potent STAT6 inhibitor with IC50 of 21 nM

AS1517499 shows potent STAT6 inhibition with an IC50 value of 21 nM. AS1517499 also inhibits IL-4-induced Th2 differentiation of mouse spleen T cells with an IC50 value of 2.3 nM and without influencing T-helper cell 1 (Th1) differentiation induced by IL-12. AS1517499 selectively inhibits Th2 differentiation without affecting Th1 differentiation[1]. In cultured human BSM cells, IL-13 (100 ng/mL) causes a phosphorylation of STAT6 and an upregulation of RhoA, a monomeric GTPase responsible for Ca2+ sensitization of smooth muscle contraction: both events are inhibited by co-incubation with AS1517499 (100 nM)[2] .

In BALB/c mice sensitized and repeatedly exposed to ovalbumin antigen, there is a notable increase in IL-13 levels in bronchoalveolar lavage fluids and phosphorylation of STAT6 in bronchial tissues following the final antigen challenge. These mice also exhibit enhanced bronchial smooth muscle (BSM) contractility in response to acetylcholine, accompanied by an upregulation of RhoA in bronchial tissues. Administering intraperitoneal injections of AS1517499 (10 mg/kg) one hour before each ovalbumin exposure significantly inhibits the antigen-induced RhoA upregulation and BSM hyperresponsiveness[2].

Normal human BSM cells (hBSMCs) are maintained in SmBM medium supplemented with 5% fetal bovine serum, 0.5 ng/mL human epidermal growth factor (hEGF), 5 μg/mL insulin, 2 ng/mL human fibroblast growth factor-basic (hFGFb), 50 μg/mL gentamicin, and 50 ng/mL amphotericin B. Cells are maintained at 37°C in a humidified atmosphere (5% CO2), fed every 48 to 72 hours, and passaged when cells reached 90 to 95% confluence. Then the hBSMCs (passages 7-9) are seeded in 6-well plates and 8-well chamber slides at a density of 3,500 cells/cm2 and, when 80 to 85% confluence observed, cells are cultured without serum for 24 hours before addition of recombin is ant human IL-13. AS1517499 (100 nM) or its vehicle (0.3% DMSO) is treated 30 minutes before the addition of IL-13 (100 ng/mL). In some experiments, AS1517499 is treated 0 (co-incubation), 3, or 12 hours after the addition of IL-13. In another series of experiments, a selective Rho-kinase inhibitor Y-27632 (1 μM) or its vehicle (0.3% DMSO) is also applied 15 minutes before the IL-13 application. At the indicated time after the IL-13 treatment, cells are washed with PBS, immediately collected, and disrupted with 1× SDS sample buffer (250 μL/well), and used for Western blot analyses[2] .

Mice[2]