Iressa, FDA Approves Drug for Lung Cancer

On June 17, 2005 the The Food and Drug Administration (FDA) has approved new labeling for gefitinib (Iressa) that limits use to patients with cancer who in the opinion of their treating physician, are currently benefiting, or have previously benefited, from Iressa treatment. In addition, AstraZeneca will distribute the drug under the Iressa Access Program. For more, please read the "Questions and Answers on Iressa's (gefitinib) New Labeling" article.

Iressa (gefitinib) is a groundbreaking new type of anti-cancer drug for people with the most common type of lung cancer. It is different from all prior chemotherapy. That is, Iressa works by uniquely blocking cellular enzymes that stimulate cell growth. So, in the future, look for the emergence of other (hopefully more effective) anti-cancer drugs that work at specific cellular or molecular sites.

With this approval by the Food and Drug Administration (FDA), patients having advanced lung cancer that is unresponsive to standard treatment now will have at least some treatment available to them. Credit the FDA for the relatively rapid availability of this drug. You see, Iressa was approved under the FDA's accelerated approval program. This program provides patients with serious disease earlier access to promising new drugs.

Leslie J. Schoenfield, M.D., Ph.D.
Medical Editor, MedicineNet.com

The Food and Drug Administration (FDA) on May 5th, 2003 announced the approval of Iressa (gefitinib) tablets as a single agent treatment for patients with advanced non-small cell lung cancer (NSCLC), the most common form of lung cancer in the US. Iressa is being approved as a treatment for patients whose cancer has continued to progress despite treatment with platinum-based and docetaxel chemotherapy, two drugs that are currently the standard of care in this disease.

Iressa was reviewed and approved under FDA's accelerated approval program, which is intended to allow patients suffering from serious or life-threatening diseases earlier access to promising new drugs. As required by the accelerated approval regulations, Iressa's developer will perform additional studies to verify the drug's clinical benefit.

"FDA believes it is crucial for cancer patients to have many safe and effective treatment options available to them in their battle against this disease" said FDA Commissioner Mark B. McClellan, M.D., Ph.D. "With the approval of Iressa, thousands of patients with lung cancer will now have access to an additional treatment after others haven't worked to stop the progression of their disease."

The mechanism by which Iressa exerts its clinical benefit is not fully understood. However, Iressa was developed to block growth stimulatory signals in cancer cells. These signals are mediated in part by enzymes called tyrosine kinases. Iressa blocks several of these tyrosine kinases, including the one associated with Epidermal Growth Factor Receptor (EGFR).

FDA based the approval on the results of a study of 216 patients with NSCLC, including 142 patients with refractory disease, i.e., tumors resistant or unresponsive to two prior treatments. The response rate (defined as at least 50% tumor shrinkage lasting at least one month) was about 10%. There were more dramatic responses in some patients and the median duration of response was 7 months. On September 24, 2002, the Oncologic Drugs Advisory Committee (ODAC) recommended that in third-line treatment of NSCLC, where there are no viable treatment options, a 10% response rate was reasonably likely to predict clinical benefit and recommended that Iressa be approved.

Results from two large, controlled, randomized trials in initial treatment of NSCLC showed no benefit from adding Iressa to standard, platinum-based chemotherapy. Therefore, Iressa is not indicated for use in this setting.

There appeared to be substantial differences in response rates in subsets of patients, with higher response rates for women (about 17%) and patients with adenocarcinoma, and with lower response rates seen in men (about 5%) and smokers.

The sponsor has agreed to conduct further studies after approval of Iressa to measure its clinical benefit. One study will evaluate Iressa treatment in patients with lung cancer resistant to two previous chemotherapy regimens and will determine whether Iressa prolongs survival compared to best supportive care. A second study will compare treatment with Iressa to treatment with an approved chemotherapy drug (docetaxel) in patients with lung cancer resistant to one previous chemotherapy regimen. The third trial will evaluate whether Iressa will decrease cancer symptoms in patients with lung cancer resistant to all available chemotherapy.

"An essential part of our accelerated approval process is the further study of the new treatment after it is on the market," said Dr. McClellan. "In the case of Iressa, studies are needed to confirm clinical benefit, understand better which patients benefit, and evaluate long-term safety."

Common side effects reported with Iressa in clinical trials were nausea, vomiting, diarrhea, rash, acne, and dry skin. Iressa may cause fetal harm when administered to pregnant women.

A significant safety concern associated with Iressa emerged just after the ODAC meeting. Reports from Japan described the occurrence of serious and sometimes fatal interstitial lung disease (ILD) in patients treated with Iressa. The FDA extended its review of Iressa by three months to review these reports. After careful review of information from all sources, including a comprehensive analysis of updated toxicity information from clinical trials and the Iressa expanded access program, involving approximately 23,000 patients, FDA determined that the incidence of ILD was approximately 2% in the Japanese experience and approximately 0.3% in the United States expanded access program, with about 1/3 of affected patients dying from this toxicity. FDA believes that this rare but serious toxicity of Iressa does not outweigh the benefits demonstrated in patients with advanced NCSLC.