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HER2, Herceptin, and Tykerb

HER2 human epidermal growth factor receptor 2) is a protein found on the surface of breast cancer cells. Some breast cancer patients have extra copies of HER2 that can be associated with more aggressive or treatment-resistant cancers. Herceptin and Tykerb are two drugs that may be used to treat breast cancer in these breast cancer patients, in combination with other breast cancer treatments. Tykerb is newly approved by the U.S. Food and Drug Administration (FDA) and is typically used in patients who have already been treated with Herceptin.

What is HER2?

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.

How Do Physicians Test for HER2?

HER2 testing is becoming more common. Knowing the results of the test can help physicians and patients determine which treatment options are most likely to be effective. HER2 testing is performed on cancer cells that have been removed during breast biopsy or breast cancer surgery. Testing may also be performed on cells from a breast tissue sample that has been stored from a previous biopsy (many laboratories keep tissue samples for years after the initial biopsy or surgery).

Testing for HER2 protein over-expression involves staining the tissue sample with a specific solution in a pathology laboratory. The pathologist then examines the cells within the tissue sample, checking for highlighted areas where high levels of HER2 over-expression are present. Depending on the level of staining, the patient’s cancer may be classified as HER2 positive or HER2 negative.

What is Herceptin?

Herceptin (generic name, trastuzumab) is a drug used to treat some women with advanced breast cancer whose cancer has spread to other areas of the body. Approved for use by the U.S. Food and Drug Administration (FDA) in September 1998, Herceptin has shown great promise in increasing patient survival time and reducing the number of deaths from advanced breast cancer. Clinical trials are also investigating whether Herceptin is helpful for women with early-stage breast cancers.

According to Genentech, the manufacturer of Herceptin, approximately 35,000 women have been given Herceptin since it first received FDA approval. However, not all breast cancer patients are candidates for Herceptin. The drug only appears to work for women whose breast cancer cells carry extra copies of a protein called HER2 (also written HER2/neu).

How Does Herceptin Work?

The drug 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. Many experts believe that Herceptin represents the future direction of breast cancer drugs in that it targets a particular protein of the cancer cell and prevents it from carrying out its action, similar to the new leukemia drug, Gleevec. Herceptin is given intravenously (through the vein) in an outpatient clinical setting.

Who is a Candidate for Herceptin?

Currently, Herceptin is FDA approved, in combination with the drug paclitaxel, to treat women with advanced, HER2 positive breast cancers.