Antigenics announces positive results of AG-707 genital herpes vaccine

Antigenics (NASDAQ: AGEN) announced positive results with AG-707, an investigational therapeutic vaccine being developed to treat herpes simplex virus-2 (HSV-2), the virus that causes genital herpes, in infected patients. Developed by Antigenics, the vaccine triggers a cellular immune response, stimulating both CD4⁺ and CD8⁺ T cells.

“We are very encouraged by these results. Recent data suggest both of these arms of immunity are needed for successful treatment of genital herpes.”

"I believe these data represent the first finding of their kind in genital herpes treatments—showing a vaccine, AG-707, elicits both CD4⁺ and CD8⁺ T-cell responses in humans," said David Koelle, M.D., study investigator and professor of Medicine, Laboratory Medicine and Global Health Medicine, University of Washington. "We are very encouraged by these results. Recent data suggest both of these arms of immunity are needed for successful treatment of genital herpes."

Data will be presented at the International Herpes Workshop annual meeting in Salt Lake City, Utah, on July 27 by study investigator, Dr. Koelle. The full data will be submitted for publication in a peer-reviewed journal.

"The obvious potential of AG-707 is in managing outbreaks and disease transmission in patients with genital herpes," added Koelle. "Being able to impact and possibly decrease the spread of genital herpes would be a huge step in stemming this epidemic."

"These results represent proof of concept for our proprietary off-the-shelf infectious disease platform. Based on our technology of integrating heat shock proteins with antigenic peptides, we could potentially create therapeutic vaccines for many infectious diseases. Our next step is to engage a partner to advance the clinical development of AG-707 in genital herpes and to pursue the broader application of the platform technology," added Garo Armen, PhD, Antigenics chairman and CEO.

STUDY RESULTS

In this four-arm, phase 1 study, 35 HSV-2 seropositive patients received AG-707+QS-21 Stimulon^® adjuvant (Antigenics proprietary saponin adjuvant), AG-707 alone, QS-21 alone, or placebo. Patients received three treatments at two-week intervals. The vaccine was well tolerated, with injection site pain as the most common reported adverse event.

All patients who were evaluable for immune response and received AG-707 with QS-21 showed a statistically significant CD4⁺ T cell response (100%; 7/7) to HSV-2 antigens as detected by IFNγ Elispot, and the majority of those patients demonstrated a CD8+ T cell response (63%; 5/8).

This study is the first to demonstrate that heat shock proteins complexed to viral antigens induce an antigen-specific T cell response in humans.