US military researchers said at a conference yesterday, Sunday 13th April, that an experimental breast cancer vaccine called E75 reduced the risk of death in patients whose tumours expressed high levels of the protein HER2/neu.

HER2-positive breast cancer represents about 25 per cent of breast cancers and has the lowest survival rates. But in this group of patients the vaccine reduced deaths by 50 per cent, researchers informed the Washington Post, just before their presentation to the American Association for Cancer Research annual meeting, in San Diego, California.

However, the results for women whose cancer expressed low or intermediate levels of HER2/neu were even better. The vaccine lowered rate of death among this group by 100 per cent. This group of patients currently relies on treatments like surgery and chemotherapy.

E75, the most advanced of all cancer vaccines, stimulates the immune system to raise levels of cytotoxic T cell (CTL) or killer T cells that target tumour cells. It is designed to prevent breast cancer recurrence in women who have already had it. Other cancer vaccines that target tumours that have already spread have not been successful.

Senior author of the study, Dr George Peoples, who is Director of the Cancer Vaccine Development Program at the US Military Cancer Institute and Chief of surgical oncology at Brooke Army Medical Center in San Antonio, told the Washington Post that:

“We now have something we think works in the majority of women with breast cancer who are currently underserved.”

Peoples said the vaccine was well tolerated, “like a flu shot”.

The small clinical trial involved 165 patients with HER2/neu tumours that had started to spread to the lymph nodes.

94 of the patients were given the vaccine (one initial shot and a booster) and 71 acted as controls.

All the women who received the vaccine showed a raised immune response, with the largest response being in those patients with low and intermediate expression of HER2/neu, reported the Post.

30 months later, although those patients with high HER2/neu expression in both the vaccine group showed similar rates of recurrence (18.2 versus 13.8 per cent), there was a 50 per cent reduction in mortality among the vaccine group.

In the low to intermediate HER2/neu expression group however, fewer than 11 per cent of the low expressors had a recurrence (compared with 18 per cent of controls), and the mortality rate in the vaccine group was zero compared to 38 per cent in the control group.

E75 is licensed under the brand name NeuVax to Arizona-based Apthera Inc, and is about to enter phase III trials for women with early stage I and stage II HER2-positive breast cancer. According to the company, so far “the clinical trial results have shown that NeuVax reduces recurrence rates while showing minimal toxicity”.

The company plans eventually to seek the approval of the US Food and Drug Administration (FDA) for NeuVax to be used to treat breast cancer with all levels of HER2 expression, in women who are at high risk of relapse or recurrence of their breast cancer.

The vaccine has also undergone a small Phase I clinical trial involving 14 patients with advanced stage IV breast cancer or advanced ovarian cancer. After receiving 8 escalating doses of NeuVax, 8 of the women showed killer T cell activity against HER2 proteins. The T cells were active for between 1 and 12 months after treatment finished, said the company.

Source: Washington Post, Apthera Inc.

Written by: Catharine Paddock, PhD