CAY10763 is a dual inhibitor of indolamine 2,3-dioxygenase 1 (IDO1; IC50= 46 nM) and STAT3 activation.1It binds to STAT3 (Kd= 530 nM) and selectively reduces the levels of STAT3 phosphorylated at the tyrosine in position 705 (STAT3Y705) over phosphorylated STAT3S727, STAT1, and STAT5 in SKOV3 cells when used at a concentration of 500 nM. It also inhibits STAT3 nuclear translocation in SKOV3 cells. CAY10763 is cytotoxic to HCT116, SKOV3, A549, and HepG2 cancer cells (IC50s = 37, 28, 33, and 12 nM, respectively). It reduces tumor growth in B16/F10 mouse melanoma and HepG2 mouse xenograft models when administered at doses of 100 and 10 mg/kg, respectively.