Brand name: Iressa
Generic: gefitinib

Medication class:  Tyrosine Kinase Inhibitor
Similar drugs:  Tagrisso (osimertinib), Tarceva (erlotinib), Zykadia (ceritinib), Gilotrif (afatinib)
Manufacturer: AstraZeneca
FDA Approval date:  July 2015

What is Iressa and how does it work?

Iressa (gefitinib) is a once-daily oral tablet that belongs to a class of drugs called tyrosine kinase inhibitors. It is used to treat people with non-small cell lung cancer (NSCLC) that has spread to other parts of the body (metastasized) who have not received prior treatment for cancer. Iressa is used to treat cancer cells that have abnormal epidermal growth factor receptor (EGFR) genes; these cancer cells are abnormal because they have EGFR exon 19  deletions or exon 21 substitution mutation.  

Epidermal growth factor receptors are found on the surface of normal and cancer cells and are involved in processes that control cell growth and how cells multiply. EGFR exon 19  deletions or exon 21 substitution mutations in lung cancer cells promote tumor cell growth, prevent death of cancer cells, promote the formation of new blood cells, and help cancer cells migrate to the rest of the body. Therefore, these EGFR mutations lead to uncontrolled growth of cancerous cells. 

Iressa blocks the action of tyrosine kinase which is an enzyme that EGFR genes use for signaling other cells and promoting cell growth and multiplication of cells. By blocking the action of tyrosine kinase, Iressa reduces the activity of EGFR genes in cancer cells. This prevents tumor cells from growing and shortens the life span of the cancer cell. Iressa affects EGFR in cancer cells more than EGFR in normal cells. 

What is Iressa used to treat?

Iressa is a first line treatment for patients with metastatic non-small cell lung cancer whose cancer cells have EGFR exon 19  deletions or exon 21 substitution mutation. Exons are coding genes in a genetic sequence. Exon 19 and 21 both code specifically for the tyrosine kinase section of the EGFR. Iressa is used to treat NSCLC in patients whose cancer cells have EGFR genes that do not have exon 19 or if exon 21 has been modified.

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