SI-109 is a potent STAT3 SH2 domain inhibitor (Ki=9 nM) with antitumor activity. SI-109 effectively inhibits the transcriptional activity of STAT3 (IC50=3 μM). SI-109 and an analog of CRBN ligand lenalidomide have been used to design PROTAC STAT3 degrader SD-36[1].
SI-109 exerts a moderate growth inhibitory activity in MOLM-16 cells (IC50=3 μM)[1].SI-109 is ineffective in inhibition of STAT3 Y705 phosphorylation and in suppression of c-Myc expression at concentrations as high as 10 μM[1].
[1]. Bai L, et al. A Potent and Selective Small-Molecule Degrader of STAT3 Achieves Complete Tumor Regression In Vivo. Cancer Cell. 2019 Nov 11;36(5):498-511.e17.