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Pharmacokinetic properties: Gefitinib is a selective epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor that is normally expressed in solid tumors of epithelial origin. Inhibition of EGFR tyrosine kinase activity can impede tumor growth, metastasis and angiogenesis, and increase tumor cell apoptosis. In vivo, gefitinib broadly inhibits tumor growth in human tumor cell-derived lines xenografted in nude mice and enhances the anti-tumor activity of chemotherapy, radiation therapy and hormone therapy. Gefitinib has been shown to have an objective anti-tumor response to locally advanced or metastatic non-small cell lung cancer and improve disease-related symptoms in clinical trials. Pharmacokinetic properties After intravenous administration, gefitinib was rapidly cleared and widely distributed, with an average elimination half-life of 48 hours.

(1) Competing for the Mg-ATP binding site in the EGFR-TK catalytic region, blocking its signaling;

(2) inhibiting the activation of mitogen-activated protein kinase and promoting apoptosis;

(3) Inhibition of tumor angiogenesis. Iressa was approved by the Japanese Ministry of Health and Welfare for the treatment of advanced NSCLC on July 5, 2002. It was approved by the FDA as a third-line treatment for NSCLC on May 5, 2003. The recommended dose is 250 mg, PO, qd.

It is worth mentioning that the FDA decision was approved after Iressa had just completed Phase II clinical trials and Phase III clinical trials had not been completed. In 2003, the Chinese Anti-Cancer Association Lung Cancer Professional Committee proposed in the treatment guidelines for inoperable NSCLC: Iressa recommended for the treatment of locally advanced or distant metastasis in patients with non-small cell lung cancer containing platinum and Docetaxel chemotherapy failure.