An irreversible pan-ErbB receptor tyrosine kinase inhibitor (IC50s = 6, 45.7, and 73.7 nM for ErbB1, ErbB2, and ErbB4, respectively); demonstrates antitumor activity in various tumor xenograft models expressing either wild-type ErbB or mutant ErbB family members that show resistance to first generation ErbB kinase inhibitors