Gefitinib

Gefitinib is an inhibitor of the epidermal growth factor receptor (EGFR) tyrosine kinase that binds to the adenosine triphosphate (ATP)-binding site of the enzyme. EGFR is often shown to be overexpressed in certain human carcinoma cells, such as lung and breast cancer cells. Overexpression leads to enhanced activation of the anti-apoptotic Ras signal transduction cascades, subsequently resulting in increased survival of cancer cells and uncontrolled cell proliferation. Gefitinib is the first selective inhibitor of the EGFR tyrosine kinase which is also referred to as Her1 or ErbB-1. By inhibiting EGFR tyrosine kinase, the downstream signaling cascades are also inhibited, resulting in inhibited malignant cell proliferation.