A potent, irreversible inhibitor of EGFR kinase activity (IC50 = 370 pM); halts cell cycling in cells that overexpress EGFR or c-ErbB2 (IC50s = 31-125 nM); profoundly blocks the growth of EGFR-overexpressing tumors in nude mice when given orally at 80 mg/kg/day for 10 days