UPDATED: Agenus' genital herpes vax cuts viral load 75% in PhII

After hitting its primary endpoint in a Phase II study last fall, Agenus ($AGEN) was already leading a Sanofi-NIH collaboration in efforts to develop the first genital herpes vaccine. Now, it's built on that lead with new Phase II results for its therapeutic candidate, HerpV, which achieved statistical significance in reducing viral load.

Agenus Chief Scientific Officer Robert Stein

The majority of the 80 patients enrolled in Agenus' trial showed an immune response after a series of HerpV vaccinations and a booster dose at 6 months, with more than half developing a robust T-cell immune response, the company said Thursday. In those patients, researchers found a 75% reduction in viral load, which has the potential to reduce the incidence and severity of herpes outbreaks and cut down on transmission of the virus.

"We are pleased that the cellular immune response observed with HerpV vaccination is associated with a significant reduction in viral replication in the genital tract," Robert Stein, Agenus' chief scientific officer, said in a statement, noting that the multiple genital herpes antigens HerpV contains may have had something to do with its success.

Currently antivirals, like GlaxoSmithKline's ($GSK) Valtrex, are the only treatment for genital herpes, and they need to be taken frequently to limit transmission by skin-to-skin contact. Agenus, on the other hand, thinks its therapeutic vaccine can make the treatment regimen more manageable--and with an estimated one in 6 Americans between the ages of 14 and 49 currently carrying the virus, it should have a sizeable patient pool if it makes it to market.

Agenus is not the only company working on a genital herpes vaccine, however. Tuesday, Genocea Biosciences ($GNCA) announced Phase I/IIa data for its own therapeutic candidate, which, at 12 months, posted a mean reduction in genital lesion rate that was 42% below baseline.

NIAID Director Dr. Anthony Fauci

And Sanofi ($SNY) and the NIH's National Institute of Allergy and Infectious Diseases (NIAID) are collaborating on a trial of a Sanofi vaccine, which is currently recruiting participants in Phase I. But while the pair is testing the vaccine's safety in adults both with and without herpes, it hopes to eventually use it to prevent infection.

"Although genital herpes is treatable, it is a lifelong infection that can exact a substantial psychological and physical toll on infected individuals and places them at higher risk of acquiring HIV. A protective vaccine would help to reduce significantly the spread of this all-too-common sexually transmitted infection," NIAID Director Dr. Anthony Fauci said last year.

- read the release
- get more on the Sanofi-NIH collaboration from clinicaltrials.gov

Special Report: Top 5 Vaccine Companies by Revenue - 2012 - Sanofi

Editor's note: This story has been updated with information on Genocea's candidate.