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Posted by balans on March 18, 2010
The news that the world's first targeted therapy, trastuzumab (Herceptin), is now available for many women with early-stage HER2-positive breast cancer may be a significant advancement in the treatment of breast cancer.
Between 25 percent and 30 percent of breast cancer is HER2-positive, meaning that growth-promoting HER2 proteins are overly abundant on the outside of the cancer cells, promoting an aggressive disease. HER2 pushes a cell to divide, and while a little on a cell is normal, a lot is not. No one knows why, in these so-called “HER2-positive” tumors, these proteins are over-expressed. But when this happens, cancer becomes aggressive.
Trastuzumab is a specific type of biologic therapy, a monoclonal antibody, designed to shut down activity of these HER2 proteins by sticking to and “smothering” them, halting the pro-growth molecular instructions that these proteins relay into the body of the cancer cells. When approved by the FDA in 1998, trastuzumab helped usher in the era of targeted therapy because it specifically attacks a molecular defect on a cancer cell.
The first use of trastuzumab, however, was in women whose cancer was the most difficult to treat, because it had spread beyond the breast. Still, when used with chemotherapy, trastuzumab reduced tumor size by more than 50 percent, and extended survival, according to investigators who conducted these clinical studies. The best response to trastuzumab was seen in patients with the highest levels of HER2 protein in their tumors, proving the therapy was truly zeroing in on the right molecular target.
The clear benefit of adding trastuzumab to chemotherapy for patients with advanced breast cancer, considering its overall tolerability, led several investigators to develop studies in the late 1990s. Researchers sought to test how the drug would treat HER2-positive cancer before it had a chance to spread. They believed that if the drug could help women with the poorest prognosis, the benefit it could offer women with the earliest stages of invasive, HER2-positive breast cancer might be dramatic.
“This advancement highlights a truly significant advance in the management of breast cancer,” stated Edith Perez, M.D., director of Mayo Clinic's Breast Clinic in Jacksonville, Fla in a prepared statement. Dr. Perez, who led one of the four pivotal studies that proved the drug's benefit in early-stage disease.
Apart from skin cancer, breast cancer is the most common cancer in American women, and due to screening, more and more women are being diagnosed with the disease. But in the last decade, breast cancer's death toll has been steadily dropping-the average survival rate five years after treatment is now more than 88 percent, according to American Cancer Society. This can be attributed to improved understanding of the disease that has led to more effective treatments.
HER-2 vaccine
A vaccine for breast cancer using the Her-2 protein is currently being developed through the leadership of a breast cancer survivor, Yvonne Paterson, Ph.D., the scientific founder of Advaxis, Inc., as well as a Professor of Microbiology at the University of Pennsylvania.
Central to the team's discovery is the microbe Listeria monocytogenes, a bacterium found in dairy products. Dr. Paterson built upon the well-known fact that when Listeria is introduced into the body, it has an extremely powerful, direct stimulatory effect on the activities of immune killer T cells. By modifying Listeria to deliver cancer antigens, Dr. Paterson was able to direct this response to kill cancer cells. These modified-Listeria vaccines harness the power of the immune system to mount an attack against the Listeria and at the same time, redirect the immune system to also attack the cancer cells.
In early studies, Dr. Paterson used the Listeria bacterium to deliver the HER-2/Neu to immune cells. These cells eventually enlist killer T cells to seek out and destroy the tumor cells that over-express the HER-2/Neu molecule. The vaccine called Lovaxin B is now in pre-clinical testing. The company, New Jersey-based biotechnology company, Advaxis, is planning on manufacturing sufficient quantities of the vaccine and is seeking FDA approval for a clinical trial.
Last September, Paterson's work was published in the Journal of Immunology, and demonstrated that a live Listeria cancer vaccine is capable of eradicating existing rapidly growing breast tissue tumors in mice. “We found that we can stop the tumor from growing out to 100 days, at which time we stopped measuring since this is a long time for experiments of this type,” said Dr. Paterson. “The tumors stopped growing or went completely away.”
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