Healthcare Industry News: HER2
News Release - December 15, 2006
Progress Reported Toward Development of a Breast Cancer VaccineSAN ANTONIO, Texas, Dec. 15 (HSMN NewsFeed) -- The long-time dream of a vaccine to prevent breast cancer may be a step closer to reality, according to new research presented Thursday at the 29th Annual San Antonio Breast Cancer Symposium. George Peoples, MD, of the Cancer Vaccine Development Laboratory in Bethesda, MD presented the results of an exciting vaccine trial targeting HER2, a protein that is related to cell growth and is commonly overexpressed in breast cancer cells. Peoples and colleagues have isolated and purified a piece of that protein, called E75, that is normally exposed on the surface of cancer cells. The purified protein is injected into patients once each month, along with factors that stimulate the immune response.
In results presented at the symposium, Dr. Peoples reported that all vaccinated patients showed a rapid increase in immunologic response up until month 4, after which the response plateaued. This immunologic response translated into a clinical response-months after the vaccination series, vaccinated patients had a 50% reduction in breast cancer recurrence compared with similar breast cancer patients who were not vaccinated.
The vaccine had minimal side effects. There was typically a local reaction around the injection site (skin reddened and warm to the touch). There were no serious systemic effects.
Current approaches to preventing breast cancer either use drugs that may have significant side effects (e.g., tamoxifen, raloxifene, and a new generation of drugs called aromatase inhibitors) or involve extreme surgery designed to remove all visible breast tissue. The possibility of a preventive vaccine with limited side effects is therefore very exciting.
Previous attempts at developing breast cancer vaccines based on injecting cancer-related proteins or pieces of proteins have shown varying degrees of success in generating an immunologic response, and only limited success in showing a clinical response. However, many of these trials were designed to treat existing tumors, rather than to prevent the growth of new tumors. One problem with this approach is that solid tumors can be extremely dense, and cells on the inside are never exposed to the vaccine. Unlike earlier attempts, this trial was aimed at preventing cancer recurrence rather than treating existing cancers-patients in the trial had high-risk cancer that had already been successfully treated, and currently had no evidence of disease, although they were at high risk for recurrence.
Another problem with earlier vaccines is that the immune system tends to be relatively tolerant to small amounts of proteins that it sees as "self" proteins -- that is, proteins that are normally present in small concentrations and that the immune system does not see as foreign. Dr. Peoples and colleagues overcame this problem by using very high doses of purified protein, and by having a long immunization schedule extending over several months.
By using their vaccine to prevent recurrence rather than to treat established breast cancers, and by using large amounts of purified protein to overcome tolerance, these researchers have been able to show both an immunologic and a clinical response, a very promising hint of things to come.
Source: San Antonio Breast Cancer Symposium
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