STAT3-IN-34 (Compound 15E) is an inhibitor for STAT3 , and inhibits the nuclear translocation and transcriptional regulator activity of STAT3. STAT3-IN-34 inhibits the proliferation of cell HaCaT with IC 50 of 0.008 μM. STAT3-IN-34 inhibits IL-17A expression and ameliorates Imiquimod -induced psoriasis in mice.