New Breast Cancer Vaccine Shows Promise In Initial Trial

By C. Rajan, contributing writer

Researchers at the Washington University School of Medicine in St. Louis have developed a new breast cancer vaccine, which has shown promising results in an initial clinical trial.

The preliminary evidence from the trial indicates that the vaccine boosts the immune systems of breast cancer patients and helps slow down the progression of cancer. The new vaccine works by targeting a protein called mammaglobin-A, which is over-expressed in up to 80 percent of breast cancers, but not in healthy tissues. Thus, it offers a specific target for treating breast cancer without harming normal cells or causing undesirable toxicity.

As an immunotherapy vaccine, it directs certain white blood cells of the body's immune system to find and attack cells carrying the mammaglobin-A protein. Because of this process, the vaccine would not work in the remaining 20 percent of breast cancer patients whose tumors do not produce mammaglobin-A.

In this initial Phase 1 trial to assess the vaccine's safety, 14 patients with advanced stage metastatic breast cancer expressing mammaglobin-A were treated with the vaccine. While the study was designed to test safety, the preliminary efficacy results indicated that the vaccine helped to slow down the tumor progression in patients, even the ones with compromised immune systems after exposure to chemotherapy.

While the control group of 12 un-vaccinated patients had 20 percent without any cancer progression after one year, the vaccinated group of 14 patients had 50 percent of patients showing no progression of their cancer one year after vaccination. The researchers say that this is a statistically significant difference, even with the small number of patients tested.

Senior author of the study, Dr. William E. Gillanders, professor of surgery, says, "Despite the weakened immune systems in these patients, we did observe a biologic response to the vaccine while analyzing immune cells in their blood samples. That's very encouraging. We also saw preliminary evidence of improved outcome, with modestly longer progression-free survival."

As the next step, the researchers plan to conduct a larger clinical trial of the vaccine in newly diagnosed breast cancer patients who have not received chemotherapy. The researchers expect that by giving the vaccine to patients at the beginning of treatment, their immune systems would not be compromised due to chemotherapy or advanced stage disease, and would thus derive more benefit from the vaccine.

Gillanders added, "We also will be able to do more informative immune monitoring than we did in this preliminary trial. Now that we have good evidence that the vaccine is safe, we think testing it in newly diagnosed patients will give us a better idea of the effectiveness of the therapy."

The study is published in the journal Clinical Cancer Research, titled “Safety and preliminary evidence of biological efficacy of a mammaglobin-A DNA vaccine in patients with stable metastatic breast cancer.”