By Randall Osborne
West Coast Editor
Continuing its run toward filing for approval, VaxGen Inc. reported that the fifth review by the Data and Safety Monitoring Board (DSMB) found the company's AIDS vaccine still safe after 23,000 vaccine injections in Phase III trials, begun in June 1998.
AIDSVAX, made from a synthetic protein, is the only preventive AIDS vaccine in the world to reach this stage of research, and the DSMB is expected to review efficacy in November.
If the interim analysis shows the vaccine works to a level of at least 30 percent, the trial likely will be halted early, and Brisbane, Calif.-based VaxGen would begin the process of filing for regulatory approval. If the findings are not conclusive, the trial will keep going until the fourth quarter of 2002.
"It has to be very statistically significant," said Nicole Lynch, associate director of communications for VaxGen. "You can't just have 11 people who got placebo and 10 who got the vaccine and got infected, and say you got 10 percent [efficacy]. With something as important as this, you don't want to get a gray answer."
About 8,000 volunteers are getting the drug, and sticking with it. As of March 18, more than 94 percent continued to participate annually in North America and Europe, where the trials are being conducted with AIDSVAX B/B mostly in at-risk white males.
"Every time a volunteer comes in for a visit, they're counseled not to engage in risky behavior," Lynch said. Volunteers are also asked about their numbers of sexual partners, and asked whether they have engaged in safe sex.
"They're counseled not to assume they have protection," Lynch said. "It would have to have an impact. Every six months you go in and talk to a nurse about HIV infection, so it's on your mind. The counseling is working, and they are decreasing their risk."
In the Thai trial, the annual participation rate was 97 percent as of March 18. That study, in Bangkok, is with AIDSVAX B/E (a different strain to address the different type of disease in that region), and targets injection drug users.
The double-blind studies inoculate subjects during a 36-month period, some given the drug and some given the placebo. VaxGen, the participating clinics and volunteers are not informed regarding who gets the drug, and who gets the placebo.
"That was actually the DSMB's call," Lynch told BioWorld Today. "There's one person, our statistician on the board, who can break the code, so to speak. Even when they review for safety, we present the data, and they go into a closed-door session, and they don't get the information in vaccine/placebo [form]. They get it as group A and group B, and they don't know which is which. As long as there's not a huge difference between them, [the board] is not going to be worried about it."
Efficacy of the vaccine will be determined by comparing HIV infection between the two groups. Made from a recombinant copy of "the sticky glycoprotein that's all over HIV's surface, which is how it latches onto a human cell," the vaccine - if it works - will prompt the body to generate antibodies against that glycoprotein.
News of yet another safety milestone passed encourages the company, which was beset by naysayers in the beginning, Lynch said.
"All kinds of people were shouting from the tree tops that we wouldn't be able to enroll the trial, or keep people in the trial, and also that people will increase their risk behavior as a result of their participation," she said, adding that none of this has proven true.
The company disclosed the latest DSMB findings after the market closed Thursday. The market was closed Friday. VaxGen's stock (NASDAQ:VXGN) ended Thursday at $21.94, down 46 cents. n