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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.
Additional Resources and References
- The March 13, 2007 FDA news release, "FDA Approves Tykerb for Advanced Breast Cancer Patients," was posted on the
FDA's website, http://www.fda.gov/
- The March 13, 2007 GlaxoSmithKline news release, FDA approves Tykerb® (lapatinib) in combination with
Xeloda® (capecitabine) for the treatment of advanced or metastatic breast cancer in women who have
progressed on prior therapy," was posted on GlaxoSmithKline's website, http://www.gsk.com/
- To learn more about HER2 or Herceptin, please visit http://www.imaginis.com/breasthealth/herceptin.asp
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