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Genocea Touts Early Look at Placebo-Controlled Herpes Vaccine Study

Xconomy Boston — 

To date, the studies Genocea Biosciences has run have not made clear how much better its experimental genital herpes vaccine is than a placebo at treating patients with the infection. Genocea is touting new results today that bolster its case for the vaccine, but which still leave some questions for the company to answer going forward.

Genocea (NASDAQ: GNCA) provided an early look at its ongoing, placebo-controlled, mid-stage trial of GEN-003, and said that so far the experimental vaccine has hit its mark. One of two tested doses of the vaccine led to a statistically significant reduction of what’s known as “viral shedding”—when the patient is releasing the virus and is contagious—compared to a placebo. Patients got three injections of GEN-003 or a sham—one every 21 days—and were then observed 28 days later.

The dose that succeeded—the one Genocea is taking forward into further testing—led to a 40 percent reduction in viral shedding, compared to a 6 percent increase for placebo patients. The dose that failed led to a 27 percent reduction, and didn’t hit statistical significance.

Genocea will now follow these patients and report results after six and 12 months of GEN-003 treatment. It’ll be hoping to see that the viral shedding results that it’s seen translate to fewer outbreaks of blisters and sores—a more important indicator of disease control.

Genocea didn’t provide many details on GEN-003’s safety, but said there were no serious side effects and that patient dropouts were “low and similarly distributed” between those on the drug and placebo.

The data are an interim look at an ongoing study, but match the best evidence the company has generated so far that GEN-003 can separate itself from a placebo. How these early results translate into an impact on lesions will be important to watch, because in one of its earlier mid-stage trials, Genocea found that 28 days after their third and final shot, even patients receiving placebo saw a statistically significant reduction in lesions compared to baseline. Genocea didn’t report on GEN-003’s impact on lesions 28 days after the last shot this time around, so the results will become more clear as time goes on and Genocea accrues and reveals more data. CEO Chip Clark (pictured) said in a statement that in previous testing of GEN-003, this type of reduction in viral shedding early on has “translated into a significant impact on genital herpes clinical disease” that lasts at least 12 months.

Shares of Genocea jumped nearly 20 percent in pre-market trading before heading in the other direction. They were down 6 percent from their $5.72 Wednesday closing price of 10:45 a.m. Thursday.

More than 400 million people worldwide have genital herpes, according to Genocea. The Centers for Disease Control and Prevention estimates that there are about 776,000 new cases annually in the U.S.  Today, people with the infection typically take oral antiviral drugs like valaciclovir (Valtrex) either to treat outbreaks, or daily to keep their herpes in check. Genocea is developing GEN-003 for the more common form of herpes, herpes simplex virus 2, hoping to provide a long-lasting alternative, or complement, to antivirals.

GEN-003 is a critical product for Genocea. A second experimental vaccine, for pneumococcus, failed a mid-stage trial later year, leading Genocea to suspend its development. GEN-003 is the company’s only potential product in clinical testing. Genocea’s vaccines are meant to trigger responses both from B cells (the ones that produce antibodies) and T cells. All of the currently approved vaccines work in a more limited way, by teaching B cells to fight microbes.