WASHINGTON, DC — An investigational therapeutic genital herpes vaccine has shown significant antiviral activity in a phase 2 trial, said researchers speaking here at the American Academy of Dermatology (AAD) 74th Annual Meeting.
The vaccine, currently named GEN-003, is a first-in-class immunotherapy composed of two immunogenic antigens and a matrix adjuvant, designed to induce both T-cell and B-cell immune responses. The vaccine is a product of Genocea Biosciences, which funded the study.
"GEN-003 is a promising vaccine. If it gets approved, it would be the first therapeutic vaccine for genital herpes or any other infectious disease," said Zeena Nawas, MD, a research fellow at the Center for Clinical Studies, Houston, Texas.
Indeed, session moderator Joel M. Gelfand, MD, medical director of the Clinical Studies Unit and associate professor of dermatology at the University of Pennsylvania, Philadelphia, told Medscape Medical News, "It's a Holy Grail of medicine to have a vaccine against this disease. Valacyclovir has to be taken forever. Something that potentially gives sustained decreased shedding and sustained decreased symptoms would be a major advance, no question."
In the phase 2, randomized, double-blind, placebo-controlled study, 310 patients with herpes simplex virus 2 infection were randomly assigned to one of seven dose groups: 30 or 60 μg of antigen combined with 25, 50, or 75 μg adjuvant, or placebo.
Three doses of vaccine were given 3 weeks apart. The patients were asked to perform genital swabbing twice daily for 28 days before receiving the first vaccine dose, again immediately after the third dose, and again at months 5 or 6 and 11 or 12. Blood samples were also collected at those points, with both viral DNA and immune responses measured. Patients were also asked to record the start and stop dates of lesions during outbreaks.
At 6 months, statistically significant reductions in viral shedding were seen in all the active vaccine groups. The most effective dose combination was the 60 μg antigen/75 μg adjuvant, which showed a 55% reduction in shedding.
In answer to a question from the audience about whether a 55% reduction in viral shedding is clinically significant, Dr Nawas responded, "Absolutely. If we have less shedding, the risk of transmission will be far less."
Significant reductions in lesions were also seen in all active vaccine doses, as well as with placebo. It is possible that patients expected to see a reduction, so that is what they reported, or it may be that the follow-up period was too short, Dr Nawas speculated, adding that the 12-month data will be available later this year.
Grade 3 systemic adverse events were infrequent, and discontinuations resulting from reactogenicity or adverse events occurred in just zero, one, or two subjects from each dose group. Most adverse events were mild, and they included myalgia, fatigue, and pain or swelling at the injection site.
"Patients care more about symptoms and signs of disease than they do about asymptomatic shedding," Dr Gelfand told Medscape Medical News, noting that the placebo response for lesions is a limit of the study. Nonetheless, he added, "it certainly seems promising."
Dr Nawas has disclosed no relevant financial relationships. Dr Gelfand disclosed that he has consulted for or received grant funding or honoraria from AbbVie, Amgen, Celgene Corporation, Coherus Biosciences (Data Safety Monitoring Board), Eli Lilly and Company, Elsevier Inc, Janssen Pharmaceuticals Inc, Leo Pharma Inc, Merck & Co Inc. (Data Safety Monitoring Board), Novartis Pharmaceuticals Corp, Pfizer Inc, Regeneron, and Sanofi US Services.
American Academy of Dermatology (AAD) 74th Annual Meeting. Presented March 5, 2016.
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Cite this: Investigational Therapeutic Genital Herpes Vaccine Promising - Medscape - Mar 05, 2016.
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