FDA Approves New Breast Cancer Drug, Tykerb (dateline May 14, 2007)
The U.S. Food and Drugs Administration (FDA) has approved the use of a new drug, Tykerb (generic name, lapatinib) for advanced breast cancer patients. Tykerb can be used along with another drug, Xeloda (generic name, capectabine). Tykerb is a targeted breast cancer treatment that may be effective for women whose breast cancers who carry extra copies of HER2, a protein that is associated with aggressive breast cancers. Another drug, Herceptin (generic name, trastuzumab) has been FDA-approved for almost a decade to treat HER2-type breast cancers. However, Tykerb works differently than Herceptin and researchers believe that it might be helpful for patients who have been treated in the past with Herceptin but who are no longer responding to it.
"Today's approval is a step forward in making new treatments available for patients who have progression of their breast cancer after treatment with some of the most effective breast cancer therapies available," said Steven Galson, MD, M.P.H., Director of FDA's Center for Drug Evaluation and Research, in an FDA news release. "New targeted therapies such as Tykerb are helping expand options for patients."
HER2 (human epidermal growth factor receptor 2) is a protein found on the surface of cells that, when functioning normally, has been found to be a key component in regulating cell growth. However, when the HER2 protein is altered, extra HER2 protein receptors may be produced. This over-expression of HER2 causes increased cell growth and reproduction, often resulting in more aggressive breast cancer cells.
HER2 protein over-expression affects approximately 20% to 30% of breast cancer patients. Women with HER2 over-expression may not be as responsive to standard breast cancer treatments, including certain regimens of chemotherapy.
The drug Herceptin has been approved by the FDA since 1998 to treat advanced HER2 positive breast cancer. Herceptin is a monoclonal antibody engineered through biotechnology. It targets breast cancer cells that have too many copies of the HER2 protein. After it has identified which cells over-express the HER2 protein, Herceptin attaches itself to the HER2 protein receptors on the surface of these cells. By binding to the cells, Herceptin slows the growth and spread of tumors that have an overabundance of HER2.
Unlike Herceptin, the newly approved Tykerb is a kinase inhibitor that works through multiple pathways to deprive tumor cells of signals needed to grow. Tykerbis a small molecule that enters the cell and blocks the function of this and other proteins. Because of this difference in mechanism of action, the FDA says that Tykerb works in some HER2 positive breast cancers that have been treated with trastuzumab and are no longer benefiting.
Before approving Tykerb, the FDA examined data from the drug's maker, GlaxoSmithKline. The data included 400 women with advanced, HER2 positive breast cancer. Half of the women were given Tykerb with Xeloda and the other half were given Xeloda alone. The results of the study showed that the women who received Tykerb with Xeloda had a statistically significant improvement in the time to tumor progression. The tumor response rate was also higher among these women. GlaxoSmithKline is continuing to study Tykerb with breast cancer patients as well as those with other types of cancers to see if the drug could be useful for other patients too.
According to the FDA, common side effects of Tykerb included diarrhea, nausea, vomiting, rash and hand-foot syndrome which may include numbness, tingling, redness, swelling and discomfort of hands and feet. Some patients also experienced generally reversible heart problems left ventricular ejection fraction, which can cause shortness of breath. In comparison, side effects of Herceptin include fever, chills, weakness, nausea, (especially when given with chemotherapy), diarrhea, and increased cough. Less common side effects of Herceptin include heart problems, loss of white blood cells (leukopenia), and fatigue or difficulty breathing due to a reduction of red blood cells (anemia).
Some researchers believe that targeted therapies are the future of cancer treatment. Since cancer characteristics differ from person to person, tailoring and applying targeted therapies to an individual cancer could increase the chances for successful treatment.