Gefitinib is a drug used in the treatment of certain types of cancer

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