GeoVax Labs Presents New Findings on Potential HIV Vaccine at 2012 Conference on Retroviruses and Opportunistic Infections (CROI)
Study Suggests Scientists May Be One Step Closer to a Vaccine That Protects Against Multiple Exposures to HIV Infections
ATLANTA, March 7, 2012
ATLANTA, March 7, 2012 /PRNewswire/ -- Harriet L. Robinson, Ph.D., Chief Scientific Officer at GeoVax Labs, Inc. (OTCQB/OTCBB: GOVX), a biotech company specializing in the development of HIV/AIDS vaccines, announced the results of a study suggesting that scientists may be one step closer to a vaccine that protects against multiple exposures to HIV infections. The study results were unveiled by Dr. Robinson during a presentation in Seattle at the 2012 Conference on Retroviruses and Opportunistic Infections (CROI).
Dr. Robinson, working alongside Rama Rao Amara, Ph.D., Associate Professor of Microbiology and Immunology, Yerkes National Primate Research Center, and member of the Emory Vaccine Center, tested a novel vaccine against HIV/AIDS for the ability to protect non-human primates against a series of 36 exposures to simian immunodeficiency virus (SIV) given in three clusters of 12 each over more than 2.5 years. The serial exposures were initiated using the SIVE660 virus that is genetically distinct from the vaccine, followed by exposure to SIV251, the most potent strain of SIV used in non-human primate studies.
The high protective activity of the vaccine is achieved by co-expressing granulocyte-macrophage colony-stimulating factor (GM-CSF) in the DNA vaccine used to prime the vaccine response. GM-CSF is a normal human protein that promotes the initiation of immune responses. By co-expressing GM-CSF and HIV proteins in the DNA vaccine, GM-CSF is present at the site of vaccination where it enhances the ability of the vaccine to elicit blocking antibodies for the virus. Blocking antibodies can stop a virus before it infects cells.
The vaccination regimen consisted of two DNA inoculations at months 0 and 2 to prime the vaccine response and then two booster inoculations at months 4 and 6. The booster vaccine was MVA, a recombinant poxvirus expressing HIV proteins. Six months after the last vaccination, both vaccinated and unvaccinated animals were exposed to a primate version of the HIV virus SIVE660 to see if the vaccine was protective. An 87% per exposure vaccine efficacy was achieved against a 1st series of 12 weekly exposures to SIVE660 with 5 out of 7 vaccinated animals being protected and none of the 9 animals in the unvaccinated group being protected. The 5 uninfected animals were rested for a year, boosted once with the MVA vaccine, rested for a half year and again exposed to 12 challenges with SIVE660. For this 2nd series of exposures, an 82% per exposure vaccine efficacy was achieved with 4 out of 5 animals being protected whereas unvaccinated animals had become infected. At this point the 4 uninfected animals were rested for 6 more months and then serially exposed to the highly potent SIV251 simian version of the HIV virus. For this last challenge, an 84% per exposure vaccine efficacy was achieved with 3 out of 4 animals not acquiring infection until the 11th or 12th challenge. Protected animals did occasionally show low indications of virus, but these were transient, seen at only one bleed, and appear to have represented locally controlled infections or false positives. No other HIV vaccine candidate currently in human clinical testing has achieved this level of preclinical success in non-human primates.
"Repeated virus challenges in animals are used to mimic sexual transmission," explained Dr. Robinson. "The hope is that the results in the non-human primate models will translate into vaccine-induced prevention of infection in humans."
"Excellent results like these give the industry hope that an effective HIV vaccine with long-lasting protection is not far from reality, and bolster our confidence that we are on the right track," says GeoVax's CEO, Dr. Robert McNally.
CROI is a scientifically focused meeting of the world's leading researchers working to understand, prevent, and treat HIV/AIDS and its complications. The goal of CROI is to provide a forum for translating laboratory and clinical research into progress against the AIDS epidemic. Over 4,000 leading researchers and clinicians from around the world convene in a different location each year for the conference.
The first generation GeoVax vaccine that does not co-express GM-CSF has shown excellent safety and reproducible vaccine responses in Phase 1 and Phase 2a clinical trials in over 400 uninfected people. These trials, supported and conducted by the U.S. National Institutes of Health HIV Vaccine Trials Network, set the stage for the 2nd generation GM-CSF co-expressing vaccine to move from its initial Phase 1 safety testing (slated to start in March of this year) to a Phase 2b efficacy trial in participants who are at high risk of exposure to HIV. The vaccine is designed for the "clade B" version of the HIV virus prevalent in the Americas. Since 1989, the United States, despite education and availability of drugs, has consistently suffered about 55,000 new infections per year. And according to a 2010 study by the U.S. Centers for Disease Control (CDC), of those individuals in the United States who are diagnosed with HIV, only 35% ultimately achieve viral load suppression through drug treatment. Thus, there is an obvious need for therapies to complement drug treatment.
About GeoVax Labs, Inc.
GeoVax is a biotechnology company developing human vaccines for diseases caused by HIV. Our goals include developing HIV/AIDS vaccines for global markets, overseeing the manufacture and testing of these vaccines under GMP/GLP conditions (FDA guidelines), conducting clinical trials for vaccine safety and effectiveness, and obtaining regulatory approvals to move the product forward. GeoVax's vaccines are unique in expressing virus like particles that display the trimeric membrane bound form of the HIV-1 envelope glycoprotein. All preventative Phase 1 human clinical trials conducted to date tested various combinations and doses of our DNA and MVA vaccines, their ability to raise anti-HIV humoral (antibody) and cellular (cytotoxic T cell) immune responses, as well as, the vaccines' safety. Successful results from Phase 1 testing supported Phase 2 testing in an ongoing, fully enrolled, 299 participant trial in North and South America . GeoVax is also enrolling volunteers in a Phase 1/2 therapeutic trial for individuals already infected with HIV. For more information, please visit www.geovax.com.
Forward-Looking Statements
Certain statements in this document are "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act These statements are based on management's current expectations and are subject to uncertainty and changes in circumstances. Actual results may differ materially from those included in these statements due to a variety of factors, including whether: GeoVax can develop and manufacture its vaccines with the desired characteristics in a timely manner, GeoVax's vaccines will be safe for human use, GeoVax's vaccines will effectively prevent AIDS in humans, vaccines will receive regulatory approvals necessary to be licensed and marketed, GeoVax raises required capital to complete vaccine development, there is development of competitive products that may be more effective or easier to use than GeoVax's products, GeoVax will be able to enter into favorable manufacturing and distribution agreements, and other factors, over which GeoVax has no control. GeoVax assumes no obligation to update these forward-looking statements, and does not intend to do so. More information about these factors is contained in GeoVax's filings with the Securities and Exchange Commission including those set forth at "Risk Factors" in GeoVax's Form 10-K.
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