Iressa is made by AstraZeneca UK Limited for AstraZeneca Pharmaceuticals, LP. AstraZeneca withdrew Iressa from the U.S. market. However, the company still manufactures the medication for use in other countries.
Iressa belongs to a group of medications known as tyrosine kinase inhibitors. Tyrosine kinases are naturally occurring proteins in the body that help regulate cell growth, among other things.
Iressa works by blocking the action of a specific tyrosine kinase known as epidermal growth factor receptor tyrosine kinase (EGFR-TK). EGFR-TK tells cancer cells to grow and divide. By blocking the action of EGFR, Iressa may slow down or stop the growth of cancer tumors.
Iressa has been studied in a variety of clinical trials for the treatment of non-small cell lung cancer. In one of these studies, 10.6 percent of people with non-small cell lung cancer had tumors that responded to Iressa after failing at least two previous chemotherapy regimens. This study did not assess whether Iressa improved survival.
In a study that evaluated the effect of Iressa on survival, people with non-small cell lung cancer whose disease progressed despite previous treatment, or who could not tolerate previous treatment, were given either Iressa or a placebo (a "sugar pill" that does not contain any active ingredients). People given Iressa lived 5.6 months, while those who were given a placebo lived 5.1 months.
In two other studies, Iressa was used in combination with standard first-line chemotherapy for the treatment of non-small cell lung cancer. In these studies, the addition of Iressa did not extend the life of people who had not previously been treated with chemotherapy. It also did not provide any benefit in the time it took for the cancer to progress or how well the tumors responded to treatment.