An inhibitor of EGFR and ErbB2 (IC50s = 0.5 and 14 nM, respectively); increases the cytotoxicity of adriamycin in a concentration-dependent manner in multidrug-resistant A549T lung cancer cells overexpressing P-glycoprotein; reduces tumor growth in ErbB2-amplified NCI-N87 and NUGC4 gastric cancer mouse xenograft models at 20 mg/kg