February 28, 2002
The second approach for a preventive AIDS vaccine ever to enter final stage Phase III human testing is scheduled to do so this year in Thailand, sponsored by the US government.
28 Feb 2002 - The vaccine trial, which will study thousands of volunteers over multiple years, will test two candidate AIDS vaccines administered in combination. The first vaccine is ALVAC, manufactured by the French pharmaceutical company Aventis Pasteur. The second vaccine is AIDSVAX, made by the California biotechnology firm VaxGen. Like other preventive AIDS vaccines in development, both ALVAC and AIDSVAX are intended for those uninfected with HIV, to teach their immune systems to be able to fight off HIV infection or AIDS should they later be exposed to the virus.
The ALVAC-AIDSVAX combination has been extensively tested in humans in earlier studies and found to be safe and, in some of those immunized, able to stimulate an anti-HIV immune response. But because only preliminary testing has been conducted, researchers do not yet know whether these immune responses are effective in preventing HIV infection or AIDS. This key question will be answered by the upcoming Thai study, a Phase III human trial. Phase III is the final stage of testing that a vaccine must pass before it can be licensed for widespread use.
"With nearly 15,000 new HIV infections each day, a preventive vaccine is the world's best hope to stop the spread of the epidemic. This global emergency demands that we do everything we can to find a vaccine as quickly as possible," said Seth Berkley, MD, President and CEO of the International AIDS Vaccine Initiative (IAVI).
In the 20-year history of AIDS, no candidate vaccine has ever completed all three required phases of human trials. And just one other vaccine approach has begun Phase III studies: VaxGen is testing its AIDSVAX product administered alone. Trials of AIDSVAX alone are underway in North America, Europe and Thailand, with results from the North America and Europe testing due late this year.
"We remain extremely optimistic that an AIDS vaccine is possible, but we also know that it is unlikely we will get it right with just a few tries. For this reason, it is critical that numerous other approaches for an AIDS vaccine are moved forward as well, rapidly and in parallel," Dr. Berkley said.
Both vaccines to be tested in Thailand consist of only pieces of HIV, not the whole virus, and therefore cannot cause AIDS. ALVAC contains HIV genes inserted into a canarypox virus, which is harmless in humans. AIDSVAX contains synthetic gp120, a protein on HIV's surface.
The ALVAC-AIDSVAX trial will be conducted by the US National Institutes of Health (NIH) and the US Department of Defense's Walter Reed Army Institute of Research. Both agencies had once planned to conduct separate Phase III trials of ALVAC-AIDSVAX, but now just one trial will be run jointly. NIH and the Walter Reed Institute, previously independent agencies, have been merged under a government restructuring.