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effort to test this theory enrolled 143 volunteers with a history of moderate-to-severe, recurrent HSV-2 infections—or, those who have between 3 and 9 outbreaks of genital lesions per year, according to Clark. Those patients, recruited at seven clinics in the U.S., were broken into groups and randomly given small (10 micrograms), medium (30 micrograms), or large (100 micrograms) dosed injections of GEN-003, or a placebo. Each patient in each vaccinated group was given three total injections—one every three weeks. Genocea then used samples that patients collected themselves twice a day to track both B cell and T cell response, and the rate of viral shedding.
“To be clear, you don’t have symptoms unless you have viral shedding. We powered the study for viral shedding because there are way more [of these] events, than outbreak events,” Clark says.
In those purely scientific measures, the study is on track. Genocea reported that patients who got the vaccine saw that viral shedding reduced by up to 51 percent at the highest dose, compared to no decline whatsoever among the placebo group. That number, which Genocea says was statistically significant, or unlikely to be due to chance, correlated with an increased response from T cells and B cells. Clark says Genocea will now track those patients over the course of a year, and see how durable the vaccine’s response is.
While these results are the first indication Genocea has that it may be on to something, regulators are going to want to see this translate into a clinical benefit. So Genocea’s first real big test will come next year, when it starts a second trial that will likely be judged both by viral shedding rates and a reduction in symptoms.
Clark says that while the current study doesn’t sink or swim on symptom reduction, Genocea is still tracking it. So far, Clark cites one encouraging data trend. In an “exploratory” analysis the company did after 119 days of follow-up, one of the groups that got GEN-003 is showing a “strong trend” in the delay between an injection and the next occurrence of symptoms, according to Clark. On average, he says, the placebo patients saw their first recurrence occur 45 days after starting a regimen. By comparison, more than half of the patients in one of the groups getting GEN-003 (Clark declined to identify which) haven’t yet experienced an outbreak, he says.
“It’s too early to tell that that’s significant—if it were significant it would be a very meaningful difference, of course, but that’s still to be seen,” he says.
Genocea will have all the data from this study in the second quarter of 2014, and then likely test the same type of patient population with the two highest doses it is currently administering to patients in its second trial.
While GEN-003’s first day of clinical reckoning is a ways away, the potential payoff, should it prove to provide a real benefit, is big. Clark says between the U.S., U.K., France, Germany, Italy, Canada, and Japan, there are about 12 million people who are both affected with HSV-2 and showing symptoms. If Genocea were to price GEN-003 against the typical vaccine, it would amount to between $100 to $300 per patient, per year, creating a market opportunity worth more than $3 billion at the high end of the range, he says.
Today, people with HSV-2 typically take oral antiviral drugs like valaciclivir (Valtrex) either only when they have outbreaks, or daily. Genocea envisions HSV 2 patients combining those antivirals with periodic shots of GEN-003—how often isn’t known as of yet given Genocea doesn’t know how long the immune response lasts.
“They work by complementary mechanisms of action and so the protection should be increased in combination,” Clark says. “We haven’t proven that yet, of course, but that’s a reasonable theory that we would expect to test at some point.”
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