Business Wire - Tuesday February 9, 1999

This marks the first efficacy trial of a preventive vaccine against HIV to take place outside of North America.

The Phase III trial in Bangkok will start this month among 2,500 HIV-negative volunteers who are at high-risk of contracting HIV infection because of injection drug use. The clinical trial will be performed in 17 methadone drug treatment centers of the Bangkok Metropolitan Administration (BMA).

"This is a critical milestone," said Seth Berkeley, M.D., president of the International AIDS Vaccine Initiative, a science-based non-profit organization. "Most AIDS vaccine research has been focused on the epidemic in industrialized countries. We applaud VaxGen for its work in Thailand and on HIV epidemics in developing countries, and we urge other vaccine makers to follow its example."

The Phase III trial in Thailand parallels the Phase III trial underway in North America with the AIDSVAX B/B' vaccine. The North American trial is being conducted in 5,000 HIV-negative volunteers who are at-risk for sexual transmission of HIV. This trial will be performed in over 40 clinical sites across the U.S. and Canada.

Multinational clinical trials of AIDSVAX are necessary to address the subtypes of HIV that cause epidemics in different regions of the world. AIDSVAX B/E, tested in Thailand, induces antibody to HIV subtypes common to South Asia, Southeast Asia and countries of the Pacific Rim. These HIV subtypes are not common in the Western Hemisphere. AIDSVAX B/B', tested in North America, induces antibody to HIV subtypes that are found in the Americas, Europe, the Caribbean and Australia, but rarely in Asia.

Collectively, the two AIDSVAX vaccines (B/B' and B/E) are designed to protect against HIV in countries where up to three billion people remain at risk. In addition to testing its initial two vaccines, VaxGen said it will be investing in research to develop formulations of AIDSVAX that will protect against HIV subtypes found in China, India and Africa.

"VaxGen's primary goal is to develop HIV vaccines that can be used worldwide to halt this dreadful epidemic," said Donald P. Francis, M.D., president of VaxGen. "The Thai government is one of the world's most committed to addressing this epidemic and has been preparing to conduct efficacy trials of a preventive HIV vaccine since the early 1990's. We at VaxGen are proud and honored to work with them to help fight this disease."

Conduct of the Phase III clinical trial for AIDSVAX B/E will be led by the Department of Health of the BMA, in collaboration with VaxGen, and the Mahidol University Faculty of Tropical Medicine in Bangkok. The Centers for Disease Control and Prevention (CDC) of Atlanta will also provide technical support to the trial through the HIV/AIDS Collaboration, a joint activity of the Thai Ministry of Public Health and CDC.

International support of the Phase III trials in Thailand was also furthered by the Joint United Nations Programme on AIDS (UNAIDS). UNAIDS provided funding to help establish the cohort of IDUs to assess the feasibility of conducting a Phase III HIV vaccine trial at the Bangkok clinical sites, and then played the role of independent reviewer of the AIDSVAX B/E clinical protocols at the request of the Thai Ministry of Public Health.

VaxGen is also collaborating with the CDC. The CDC has provided assistance to VaxGen by helping to organize the company's first international trial. CDC has worked closely to help the Thai government prepare to implement this trial and will be providing technical assistance throughout the vaccine trial. In addition, the collaboration between VaxGen and CDC has been expanded to include long-term scientific studies associated with the outcome of the Phase III trials in Bangkok.

AIDSVAX is a preparation of gp120, the HIV envelope protein that binds to the surface of T-cells. The gp120 is manufactured by recombinant DNA technology. Each AIDSVAX formulation is bivalent - that is, created from recombinant copies of the gp120 protein from the surface of two types of HIV. Injecting gp120 into the body stimulates the production of antibodies that, in any future exposure to HIV, would hopefully prevent infection. Phase I/II clinical trials of AIDSVAX in both the US and in Thailand have shown that it is safe for use in humans (the synthetic gp120 is incapable of causing HIV infection in inoculated people) and induces a strong immune response in over 99 percent of recipients.

HIV has several subtypes of which five effectively cover 95 percent of the epidemic. They are classified as A, B, C, D and E, according to the order of discovery. These viral subtypes have spread worldwide as several independent, but large epidemics. VaxGen has addressed this global spread through a unique strategy. It has developed a generic vaccine structure, AIDSVAX, which is adaptable to regional epidemics by substitution of different gp120 proteins. The result is that with a handful of AIDSVAX formulations, the company believes that it can provide global coverage for the entire HIV epidemic. Already, the current B/B' and B/E formulations of AIDSVAX address two of the three most serious epidemics in the world.

A Phase III trial is designed to determine if a vaccine is effective in protecting against infection or disease; it is the final and most important step in the evaluation process before a vaccine is considered for licensure by the FDA. The Thai trial will be a randomized, double-blind, placebo-controlled trial, in which half of the participants will receive vaccine and half will receive placebo (inactive substance). Neither the researchers nor the participants know who will receive vaccine and who will receive placebo. At the end of the trial, the patient code is opened and the number of infections in the vaccine group is compared to the number of infections in the placebo group in order to determine the vaccine's effectiveness. All volunteers participating in both the North American and Thai trials will receive extensive counseling on how to protect themselves from HIV infection as well as explicit warnings that trial participation may not protect them from infection.

VaxGen, Inc., based in Brisbane, Ca., is a biotechnology company committed to making an HIV vaccine for worldwide use.

Additional information is available on the company's web site at: www.vaxgen.com

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