Background:

SH-4-54 is a potent inhibitor of STAT3 with KD values of 300 and 464 nM for STAT3 and STAT5, respectively [1].

STAT3 is a transcription factor that belongs to the STAT transcription factor family. STAT3 signaling plays an important role in the survival and proliferation of brain tumor stem cells (BTSCs) and glioblastoma (GBM) [1].

SH-4-54 is a potent STAT inhibitor. SH-4-54 inhibited interactions between STAT3 and phosphopeptide with Ki value of 10-30 μM. SH-4-54 exhibited selectivity for STAT3 against STAT1 by >10-fold. SH-4-54 inhibited pSTAT3 (Y705) in a concentration-dependent way with no effect on pSTAT3 (S727), suggesting that SH-4-54 bound to the STAT3 SH2 domain. Also, SH-4-54 reduced pSTAT3 levels and inhibited the downstream targets Cyclin D1 and Bcl-xL, which were involved in cell growth and survival [1].

In mice, intraperitoneal injection of SH-4-54 (10 mg/kg) caused a concentration of 700 nM after 30 min in the brain. In NOD-SCID mice xenografted with 105 BT73 glioma cells, SH-4-54 (10 mg/kg) reduced tumor cells and pSTAT3 expression. Also, SH-4-54 inhibited proliferation and induced apoptosis [1].

Reference:
[1].  Haftchenary S, Luchman HA, Jouk AO, et al. Potent Targeting of the STAT3 Protein in Brain Cancer Stem Cells: A Promising Route for Treating Glioblastoma. ACS Med Chem Lett, 2013, 4(11): 1102-1107.