STAT3-IN-27 (Compound 41) is an orally active inhibitor for phosphorylation of STAT3 ( K D is 4.4 μM) and STAT3 transcription ( IC 50 is 22.57 nM). STAT3-IN-27 inhibits proliferation of various cancer cells with IC 50 of 10-500 nM. STAT3-IN-27 arrests the cell cycle at G2/M phase, induces mitochondrial dysfunction and apoptosis in HCT116, inhibits cell migration of HCT116. STAT3-IN-27 exhibits antitumor efficacy in mouse model.