A vaccine that may prevent HIV has been given the green light by the U.S. Food and Drug Administration to begin clinical trials in humans, according to Canadian researchers.
The announcement was made on the campus of the University of Western Ontario in London, Ont.
“We have gone through so many different challenges to come to this point,” said Dr. Chil-Yong Kang, a researcher and professor at Western’s Schulich School of Medicine and Dentistry. “This is the first time that I feel very happy and comfortable to initiate this human clinical trial.”
Scientists at the University of Western Ontario, financially backed by the pharmaceutical venture company Sumagen, developed the vaccine, which is based on a genetically modified killed whole virus. The vaccine stimulated a strong immune response in early testing and appears to have no adverse effects, according to the researchers.
“FDA approval for human clinical trials is an extremely significant milestone for our vaccine, which has the potential to save the lives of millions of people around the world by preventing HIV infection,” said Kang.
In 2009, researchers reported that an AIDS vaccine had for the first time protected people against HIV. Since then, the researchers have been wondering, How did it work?
One of the biggest black boxes in AIDS research remains the important question of what actually protects the body from HIV. Is it antibodies to the virus? Or is it immune cells that are targeted to recognize and eliminate HIV?
AIDS researchers have only been able to guess at what these critical weapons against HIV could be, which is partly why their efforts to create a vaccine have thus far been marked by a long line of failed attempts. But when the RV144 trial in Thailand showed promise in 2009, scientists finally had something to work with. The vaccine was only modestly effective — protecting just 31% of heterosexual adults from infection - especially compared with inoculations against other common infectious agents like measles or mumps, which are 95% to 98% effective. But it was a start.
He said there have been three clinical trials for an HIV vaccine in the past using live viruses. “None of the researchers in the past have used this approach,” he says of his use of a killed virus.
The vaccine, SAV001, will now have to undergo three phases of human clinical trials;
Phase 1. Beginning in January 2012, this phase will involve 30 HIV-positive people on whom safety will be retested.
Phase 2. This phase will examine immune responses in humans and will involve 600 HIV-negative people who are at high risk of contracting the AIDS virus.
Phase 3. This phase will determine the efficacy of the vaccine and will involve 6,000 HIV-negative volunteers at high risk of contracting the virus.
“This analysis has produced some intriguing hints about what types of human immune responses a preventive HIV vaccine may need to induce,” said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, which helped fund the study, along with the U.S. Army Medical Research and Materiel Command and the Bill and Melinda Gates Foundation, in an statement. “With further exploration, this new knowledge may bring us a step closer to developing a broadly protective HIV vaccine.”
And because of the way HIV works, that vaccine needs to be able to protect people immediately and powerfully. “For this vaccine, we have got have all our antibodies and killer cells and armamentarium upfront,” says Haynes. “The person has to be completely protected from infection at the time they are challenged by HIV.”
And now, with the first clues about how to develop that protection, a more effective anti-HIV vaccine might actually be possible in coming years.
By ALICE PARK