The HER2-based peptide vaccine AE37 administered to patients with breast cancer produced immunologic responses compared with a control group, according to 24-month results.
“The theory is that once you form that response to the specific peptide, if the body has a recurrence, it will recognize that cancer as a bad thing, a foreign thing,” said Diane F. Hale, MD, a research resident in general surgery at Brooke Army Medical Center in Fort Sam Houston, San Antonio, Texas. “The immune markers could lead us to potentially identify those people who may have a recurrence.”
For this prospective, randomized, single-blinded phase 2 trial, all of the 217 women enrolled previously completed standard therapy for breast cancer and were disease free at trial onset.
Half the patients (109) received AE37 and the immunoadjuvant granulocyte-macrophage colony-stimulating factor (GM-CSF), and 108 patients received GM-CSF only in 6 monthly intradermal injections.
Researchers evaluated in vivo delayed-type hypersensitivity reactions by injecting a small, nontherapeutic dose of the vaccine beneath the patient’s skin. In the vaccine group, 86% of patients showed a significant reaction, a physical reaction of greater than 5 mm, compared with 27% of patients in the control group.
In addition, researchers discovered that the vaccine group had more responders than the control group when in vitro proliferation responses were evaluated. Moreover, the latter group had more nonresponders, based on stimulation indexes.
“Naturally, the people in the vaccine group had a significant response compared with the control group because they didn’t have that immune stimulation to the HER2 peptide,” Hale said.
Upon measuring T regulatory cell responses in 107 patients, “there was a larger percentage of patients [within the vaccine group] who had a decrease in their T regulatory cells” from prevaccination baseline, Hale said. Researchers discovered a decrease of more than 90% among 41 patients assigned to the peptide vaccine versus 28 patient controls.
Source: AACR.