Antagonism Of The Stat3-Stat3 Protein Dimer With Salicylic Acid Based Small Molecules

More than 50 new inhibitors of the oncogenic Stat3 protein were identified through a structure-activity relationship (SAR) study based on the previously identified inhibitor S3I-201 (IC 50=86μM, K i\u3e300μM). A key structural feature of these inhibitors is a salicylic acid moiety, which, by acting as a phosphotyrosine mimetic, is believed to facilitate binding to the Stat3 SH2 domain. Several of the analogues exhibit higher potency than the lead compound in inhibiting Stat3 DNA binding activity, with an invitro IC 50 range of 18.7-51.9μM, and disruption of Stat3-pTyr peptide interactions with K i values in the 15.5-41μM range. One agent in particular exhibited potent inhibition of Stat3 phosphorylation in both breast and multiple myeloma tumor cells, suppressed the expression of Stat3 target genes, and induced antitumor effects in tumor cells harboring activated Stat3 protein. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim