An antibacterial and coccidiostat compound that shows selective toxicity for HMLER breast cancer stem cells (IC50 = ~24 μM); 8 μM treatment of 4T1 and MCF-7-Ras breast cancer cell lines decreases cancer stem cell growth ~2-fold and ~3-fold, respectively; 5 mg/kg inhibits mammary tumor growth and induces increased epithelial differentiation of tumor cells in mice implanted with SUM159 human breast cancer cells