Compound 56, 4-[(3-Bromophenyl)amino]-6,7-diethoxyquinazoline, is a potent and specific inhibitor of the tyrosine kinase of the epidermal growth factor receptor (EGFR) showing an IC₅₀of 0.006 nM. It competitively binds at the adenosine-triphosphate (ATP) site of EGFR. Compound 56 is capable of inhibiting the phosphorylation of EGF-dependent EGFR, suppressing the proliferation and clonogenicity of a wide panel of EGFR-overexpressing human cancer lines, and blocking EGF-mediated mitogenesis and oncogenic transformation in fibroblasts overexpressing EGFR. Besides inhibiting EGFR tyrosine kinase, It also inhibits the tyrosine kinase of human epidermal growth factor receptor 2 (HER2/neu) but with a less potency.

Reference

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