 As the type I tyrosine kinases are involved in various aspects of cell growth and survival, a potent quinazoline and pyrido-3,4-d-pyrimidine small molecule GW572016 against HER1 and HER2 was developed which showed potent in vitro inhibition of HER1 and HER2 in tumor cell lines. Mouse xenograft models of BT474 and HN5 cell lines also showed growth inhibition in a dose-responsive manner. In addition, GW572016 caused a reduction in HER1 and HER2 autophosphorylation, indicating interference of this signaling pathway. GW572016 not only inhibited baseline activation of HER1 and HER2, but also has been shown to interrupt downstream activation of Erk12 MAP kinases and Akt. 