Agenus, Sanofi-NIH collaboration race to develop genital herpes vaccine

Genital herpes is a staggeringly common infection, with an estimated one in 6 Americans aged 14 to 49 carrying the virus. Antivirals are the current treatment, but vaccines from Agenus ($AGEN) and a Sanofi ($SNY)-National Institutes of Health (NIH) collaboration are now advancing down the pipeline.

Agenus and the Sanofi-NIH collaboration both gave updates on their clinical candidates this week. The Agenus vaccine, HerpV, is leading the race, having met its primary endpoint in a Phase II trial of 80 subjects, 70 of whom received the treatment. Patients in this treatment arm experienced a 15% reduction in viral shedding--the process that makes herpes transmissible by skin-to-skin contact--and a 34% fall in viral load. The fall was achieved over a 45-day period in patients who received three injections at two-week intervals.

Studies of existing antivirals, such as GlaxoSmithKline's ($GSK) now off-patent Valtrex, have shown an up to 80% fall in viral shedding, but this is only possible when patients take the drug three times a day. Agenus thinks its therapeutic vaccine can improve on this treatment regime, and it expects to present more data from the Phase II trial to support its case in the first half of 2014. Having top-line Phase II data in the bag puts Agenus ahead of the Sanofi-NIH collaboration, which is currently enrolling people in its Phase I study.

The National Institute of Allergy and Infectious Diseases (NIAID) is sponsoring the trial, while Sanofi is listed on as a collaborator and is manufacturing the clinical candidate. Success for either vaccine candidate could end the need for daily antiviral doses. "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.

- read the Agenus release
- here's Reuters' take
- check out the NIH news