H171

H171 is a novel, nanomolar small-molecule inhibitor of signal transducer and activator of transcription 3 (STAT3) DNA-binding activity. Developed by researchers at the University of Hawaii Cancer Center and the University of Hawaii at Manoa, H171 was designed based on an N-methylglycinamide scaffold to optimize STAT3-inhibitory potency and antitumor effects. In preclinical studies, H171 demonstrated selective inhibition of STAT3 DNA-binding activity in vitro with an IC50 of 300–800 nM, showing minimal effect on STAT1 and STAT5. In human breast cancer cell lines (such as MDA-MB-231 and MDA-MB-468) harboring constitutively active STAT3, treatment with H171 inhibited STAT3 phosphorylation at Tyr705 and DNA-binding activity, leading to blocked cell growth, viability, colony formation, and oncogenic transformation.