Biotechs angling for T-cell response in race for next-gen herpes vaccine

When Australian biotech Admedus announced Phase I results for its herpes simplex virus vaccine last week, it was far from the first company to do so. Despite the current absence of a vaccine for the virus, plenty of companies have taken a stab at developing one. And now, a whole new generation of vaccinemakers are trying their hand in a race that's heating up.

Armed with data that its candidate produced a T-cell response in 19 of 20 trial participants in uninfected humans, Admedus will now move on to test a larger group of people infected with HSV-2, reported last Thursday. It'll join a growing group of companies currently in clinical trials, led by a trio comprising Massachusetts biotechs Genocea Biosciences ($GNCA) and Agenus ($AGEN) and San Diego's Vical ($VICL).

Big Pharma has been here before, too. Novartis ($NVS), GlaxoSmithKline ($GSK) and Merck ($MRK) have all taken a stab at creating a vaccine for the virus with little positive result.

Genocea CEO Chip Clark

But there's an important difference between this new crop of developers and those that have already struck out on an HSV-2 vaccine, Genocea CEO Chip Clark told FierceVaccines. And that's T cells.

"The difference between the previous generation of vaccines companies and us is that we're trying to also get T-cell responses, not just B-cell responses," he said. "We need to be able to in some way strengthen the immunoresponse to HSV. B cells are not enough."

The clinical results that the new wave of companies has generated--or will generate--are, in a way, "a referendum on a variety of approaches to getting the right T-cell response," Clark said.

And so far, data suggest that some of them could be on the right track. This summer, Genocea announced that 6 months after dosing, its GEN-003 had posted a 65% reduction in genital lesion rates in a Phase I/IIa trial, with a 40% reduction in viral shedding. Just a few days earlier, Agenus unveiled results from a Phase II study in which the majority of the 80 patients enrolled 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.

While many of the prospects currently in development are being studied for therapeutic use, the ultimate goal for each company's platform is to create a prophylactic vaccine to ward off the virus in the first place, MedCity News reports. With the virus currently infecting an estimated 500-plus million people worldwide, the potential patient pool is a large one.

But because the virus can infect people without producing visible effects, a good preventative vaccine may need to have a therapeutic component, too, Clark said.

"Many people are infected but don't know it," he told FierceVaccines. "A prophylactic typically is given to people who have not been infected, and you don't want to be in a situation where you're vaccinating and exacerbating an existing infection."

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