SI-109 is a potent STAT3 SH2 domain inhibitor ( K i =9 nM) with antitumor activity. SI-109 effectively inhibits the transcriptional activity of STAT3 ( IC 50 =3 μM). SI-109 and an analog of CRBN ligand lenalidomide have been used to design PROTAC STAT3 degrader SD-36 In Vitro SI-109 exerts a moderate growth inhibitory activity in MOLM-16 cells (IC 50 =3 μM). SI-109 is ineffective in inhibition of STAT3 Y705 phosphorylation and in suppression of c-Myc expression at concentrations as high as 10 μM. MCE has not independently confirmed the accuracy of these methods. They are for reference only. Form:Solid IC50& Target:STAT3 9 nM (Ki)