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Disappointing HSV Vaccine Results

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An experimental HSV vaccine was not effective in preventing genital HSV-2 infections or disease in women, according to data published in the New England Journal of Medicine.

As with many diseases, the quest for an effective vaccine is the holy grail of HSV research. Results from prior HSV vaccines trials teased with promise: while ineffective in men, in early studies the vaccine prevented genital herpes in more than 70% of women who were free of both HSV-1 and HSV-2 at study entry. Results from expanded research with the vaccine have been disappointing, however.

The most recent data comes from a clinical trial done with over 8,300 women who were seronegative for both HSV-1 and HSV-2 antibodies. The subjects were randomized and received a vaccine for either HSV or hepatitis A. The results in the HSV group were mixed: while the vaccine was 58% effective in preventing genital HSV-1 disease (symptoms, like sores, associated with an outbreak), it was ineffective against disease related to HSV-2 (overall efficacy against any genital HSV disease was 20%). The HSV vaccine was 35% effective in blocking genital HSV-1 infections, with no efficacy observed against genital HSV-2 infection. Infection with HSV occurs when someone simply contracts the virus, whether or not they notice any outbreaks. Because of these results, further development of this vaccine is not going to be pursued.

HSV infections are common, with the majority of adults in the U.S. believed to have HSV-1 (often in the form of oral herpes that causes cold sores). According to the Centers for Disease Control and Prevention (CDC), approximately 17% of adults in the U.S. have HSV-2, most often experienced as a genital infection.

Belshe R, Leone P, Bernstein D,Wald A, Levin M, Stapleton J, Gorfinkel I, Morrow R, Ewell M, Stokes-Riner A, Dubin G, Heineman T, Schulte J, Deal C. for the Herpevac Trial for Women. Efficacy Results of a Trial of a Herpes Simplex Vaccine. N Engl J Med, 2012. 366:34-43January 5, 2012.


Vical Vaccine

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The manufacturer of an experimental vaccine for HSV-2 that showed therapeutic efficacy in animal research has announced plans to begin human safety studies in 2012.

Vical Incorporated is a biopharmaceutical research company based in San Diego, CA. According to information posted on the company’s website, studies with guinea pigs showed their Vaxfectin® vaccine was effective in preventing recurrent lesions related to reactivation of HSV-2. The next step will be evaluating safety in human subjects and, based on the outcome of those studies, the company plans to launch early phase clinical trials to evaluate vaccine efficacy in humans “as soon as possible.”

Treatment for recurrent genital herpes currently involves oral antiviral medication, taken either at the onset of an outbreak to speed healing or as a daily, suppressive dose to curtail episodes. Daily therapy with Valtrex® has also shown the ability to reduce transmission to partners uninfected with genital HSV-2 by about half.

Read more at the Vical website.


What's New in Herpes Vaccine Research

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HerpV (formerly AG-707)
Agenus, Inc, formerly named Antigenics, Inc, reported on developments of their experimental herpes vaccine, AG-707, now renamed HerpV. HerpV is intended as a therapeutic vaccine, designed to treat, not prevent, herpes infection. In the company’s fourth quarter report for 2010, they note the success of Phase I trials, noting that “100% of evaluable patients receiving HerpV with QS-21 demonstrated a statistically significant CD4+ T-cell response to HSV-2 antigens, and a majority of those patients (63%) demonstrated a CD8+ T-cell response. Eliciting both of these types of immune responses is a first of it’s kind achievement in herpes therapy.” Agenus indicates that the findings from the trial will be submitted for publication in 2011. At present, Agenus is seeking partners for the further development of HerpV.

Patent Awarded for HSV Vaccine Candidate
In early February of this year, the biopharmaceutical company Vical, Inc., announced a patent award assigned to Vical and the University of Washington, covering DNA vaccines for HSV-2. Vical is collaborating with both the University of Washington School of Medicine and the Sealy Center for Vaccine Development on the preclinical development of an HSV-2 vaccine. The vaccine under development is designed for the treatment of HSV-2, with the goals of reducing or eliminating recurrences and viral shedding and preventing transmission.


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