Six months after saying it would re-evaluate the lung cancer drug Iressa (gefitinib), the US Food and Drug Administration has decided to let the drug remain on the market, but limit which patients can get it. The decision follows disappointing results from a clinical trial that showed Iressa does not help most patients live longer.

Beginning on September 15, 2005, only patients who are already taking the drug and benefiting from it, or those who took it successfully in the past, will be able to get Iressa. Manufacturer AstraZeneca is setting up what it calls the Iressa Access Program to provide the drug to qualified US patients through a mail-order pharmacy.

Iressa will also be available for certain clinical trials.

The FDA approved Iressa as a second-line treatment for advanced non-small cell lung cancer in 2003 because studies showed it could shrink tumors in about 10% of people who took it. As a condition of that approval, AstraZeneca had to conduct more research to find out if the drug also could help people live longer. That study, made public in December 2004, showed it didn't.

The results prompted AstraZeneca to urge doctors to consider other second-line treatments that are known to improve survival before prescribing Iressa. Those include Taxotere (docetaxel) and Tarceva (erlotinib), a drug similar to Iressa.

Now, the FDA says, new patients should not be given Iressa at all unless they are participating in a clinical trial of the drug. The agency said it is not currently considering taking Iressa off the market because studies of the drug are still in progress and new ones are being developed.

AstraZeneca said it will continue looking for biomarkers that will help predict which patients are likely to respond to Iressa. Last year, two separate groups of researchers discovered specific genetic mutations that seem to make lung tumors more susceptible to the drug.