The era of pharmacogenomics is upon us. On September 25, Genentech, Inc. (South San Francisco, CA) received U.S. Food and Drug Administration approval for the first biotech drug for treating metastatic breast cancer. The drug, Herceptin, targets the HER2 gene expressed by about 25% of all breast cancer patients and which is believed to be responsible for the aggressiveness of certain types of breast cancer.
On the same day DAKO Corp. (Carpinteria, CA) received FDA approval for HercepTest, an in vitro assay for the HER2 gene. The timing was not a coincidence, since Genentech and DAKO had been collaborating on HercepTest since at least March 1998. Nevertheless, the approval of a gene-targeting drug and an assay for the drug's potential effectiveness on the same day marks the beginning of what should be an exciting trend: the emergence of gene-based therapies and genetic tests that predict the treatments' effectiveness.
HercepText stains Breast Cancer Cells Expressing the HER2 Gene.
Under terms of the March, 1998 agreement between Genentech and DAKO, Genentech granted DAKO a license under Genentech patent rights and know-how for developing the imunohistochemical HercepTest, which quantifies overexpression of HER2, thereby identifying patients who could benefit from Herceptin (trastuzumab).
"With the FDA's approval of HercepTest, we will be bringing the first commercially available standardized test to physicians that will identify a patient's HER2 protein status and help identify those who may benefit most from Herceptin Therapy," said Viggo Harboe, president, DAKO Corporation , USA. "We are pleased by the FDA's rapid review and approval process for HercepTest. This, coupled with DAKO's successful collaboration with Genentech in this pioneering effort to bring a new drug and corresponding diagnostic test to approval at the same time, is a testament to the commitment of everyone involved working toward the common goal of finding a solution to breast cancer."
Between 25 and 30% of the approximately 180,700 women diagnosed annually with breast cancer overexpress the HER2 protein, that is, these cancers produce excessive amounts of HER2 cell-surface receptors. However, all women diagnosed with breast cancer are candidates for the HER2 test. Based on epidemiological studies, the HER2 gene confers a certain aggressiveness to breast cancer, causing it to metastasize at a faster rate than cancers in patients who do not overexpress HER2.
HercepTest Immunohistochemical Protocol.
HercepTest may be carried out on new or stored specimens of tumor tissue (figure 1). Evaluation of a patient's HER2 protein status when added to the results of other tests and the patient's overall condition help oncologists determine the best treatment regimen for each woman. Ultimately, the new IHC test will aid in the assessment of prescribing Herceptin for the patient.
HercepTest, which is based on an immunohistochemistry (IHC) antibody assay, is easy to conduct with relatively few steps and equipment routinely found in pathology laboratories (figure 2). IHC involves the use of antibodies that have been developed to identify specific molecules (antigens) of interest, such as HER2. In the case of HER2, the antigens are the HER2 cell-surface receptors. The antibodies are applied to the tissue, and their binding can be used to visualize how much antigen is present in the tissue.
For more information: Viggo Harboe, President, DAKO Corp., 6392 Via Real, Carpinteria, CA 93013. Tel: 805-566-6655.
By Angelo DePalma