It is the first selective inhibitor of epidermal growth factor receptor's (EGFR) tyrosine kinase domain
Gefitinib inhibits EGFR tyrosine kinase by binding to the adenosine triphosphate (ATP)-binding site of the enzyme.
Thus the function of the EGFR tyrosine kinase in activating the Ras signal transduction cascade is inhibited, and malignant cells are inhibited