Gefitinib. Molecular model of the chemotherapy drug gefitinib (C22.H24.Cl.F.N4.O3), used in the treatment of certain breast, lung and other cancers. It is an epidermal growth factor receptor (EGFR) inhibitor, being a selective inhibitor of the tyrosine kinase domain the receptor. Atoms are represented as spheres and are colour-coded: carbon (grey), hydrogen (white), nitrogen (blue), oxygen (red), chlorine (green) and fluorine (cyan)