Identification and characterization of small molecule inhibitors of signal transducer and activator of transcription 3 (STAT3) signaling pathway by virtual screening

Inhibition of the signal transducer and activator of transcription 3 (STAT3) signaling pathway has been considered a novel therapeutic strategy to treat human cancers that harbor aberrantly-active STAT3. In this study, a series of small molecules were identified as novel inhibitors of STAT3 signaling pathway through virtual screening. A tricyclic scaffold containing compound, 6, was identified as an inhibitor of IL-6/STAT3 signaling with an IC50 of 26.68 μM. In addition, this compound inhibited Tyr705 phosphorylation of STAT3 and had no obvious effect on upstream tyrosine kinases. Thus, compound 6 is a potential lead structure and valuable for further drug development.