Discovery of potent and selective STAT3 inhibitors against triple-negative breast cancer.

The development of effective targeted therapies for triple-negative breast cancer (TNBC) remains challenging due to its diverse molecular subtypes and intrinsically aggressive tumor biology. Constitutive STAT3 activation drives TNBC pathogenesis and confers treatment resistance, establishing it as a promising precision oncology target. In this study, LZJ66 (previously designated as compound 40) was used as the lead compound for further optimization. Among the 42 designed compounds, W36 emerged as a high binding affinity inhibitor of STAT3 (KD = 323.3 nM), demonstrating dual suppression of STAT3 phosphorylation and proliferation in the STAT3-overactivated TNBC cell lines MDA-MB-231 (IC50 = 0.61 ± 0.31 μM) and MDA-MB-468 (IC50 = 0.65 ± 0.12 μM). Its antitumor efficacy has extended to other TNBC cell lines, with dose-dependent suppression of TNBC growth in xenograft model, supporting its potential for clinical translation.