The first clinical trial for a Zika virus vaccine just received a green light from the FDA. Inovio Pharmaceuticals and GeneOne Life Science announced on Monday that their vaccine, called GLS-5700, will undergo phase I clinical testing for safety in 40 healthy volunteers within a few weeks.
Inovio’s effort has plenty of company—the National Institutes of Health, the French pharmaceutical giant Sanofi, and the India-based Bharat Biotech all have Zika vaccines in the works. Anthony Fauci, director of the NIH’s National Institute of Allergy and Infectious Diseases, previously said that scientists won’t know if Zika vaccines are working until early 2018, even in the best-case scenario. Inovio’s vaccine design is different from the others, though, and it might beat that time line since the NIH isn’t starting its clinical trials until September.
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Common strategies for viral vaccine production include using a viable but weakened virus, or using inactive viral particles to stimulate the immune system (one of several approaches that the NIH is taking).
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The Aedes aegypti mosquito is responsible for the spread of Zika virus, yellow fever, dengue fever, and other diseases.
Inovio, on the other hand, is developing a DNA vaccine, where synthetic Zika genes are inserted into a DNA-carrying vessel called a plasmid. The idea is that when injected into a patient, the body’s own cellular machinery produces bits of viral proteins from the plasmid, teaching the immune system to attack Zika. Inovio is using the same principle to develop other vaccines, including one for the flu.
DNA vaccines need a little help crossing over into cells. After the vaccine is injected, the company uses a technique known as electroporation delivery to apply millisecond-long electrical pulses into the muscle or skin and temporarily open cellular pores to let the vaccine in.
DNA vaccines carry some advantages over traditional vaccines. Because the DNA is synthetic and no actual Zika virus is used, it is safer and should be quicker to manufacture. Easy storage is another benefit. “We don’t have to keep our DNA vaccines frozen,” Joseph Kim, Inovio’s CEO, says. “If we have to send a shipment of our vaccine into the jungle, we don’t have to carry big freezers.”
But Sarah George, a scientist at the Center for Vaccine Development at Saint Louis University says that previous attempts at using DNA vaccines in humans haven’t boosted immunity as much as hoped. For Zika, things are even more uncertain. “The problem is, we don’t know what a protective immune response in Zika looks like,” she says.
Kim acknowledges that traditional vaccines using weakened or inactivated viruses generate stronger immune responses and potentially better protection. “But the downside is that it can be a lot more toxic and cause the disease you are trying to prevent,” he says.
Given that the average vaccine development time to market is over 10 years, Zika vaccine development has been a speedy endeavor thus far. Kim says it only took a couple of weeks to construct the vaccine. After that was done, they spent about six months honing it in mice and monkeys.
“The hope is that by the end of 2016 or early 2017 we have the phase I safety data,” George says. “Then, and only then, would we move onto a larger trial.”
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Right now Inovio’s vaccine is unrelated to the NIH’s vaccine efforts, though Kim says he wouldn’t be opposed to marshaling resources. “I think it is great to have multiple shots on this goal whether from the NIH or Sanofi,” he says. “But once we have the data trickling in, we need to push the best horse forward.”
