A reversible inhibitor of ErbB1/EGFR, ErbB2/HER2, and ErbB3/HER3 (IC50s = 4, 3, and 4 nM, respectively, for autophosphorylation); suppresses cell growth and induces apoptosis in SUM149 and FC-IBC-02 human breast cancer cell lines at 0.01, 0.1, and 1 μM; inhibits tumor growth in BT474c, Calu-3, LoVo, FaDu, and PC-9 mouse xenograft models from 6.25-50 mg/kg; inhibits inflammatory breast cancer tumor growth in a mouse xenograft model when administered in combination with paclitaxel at 25 mg/kg per day