If it works in humans -- and if it's inexpensive -- it could save millions of lives. Women in many AIDS-devastated nations have limited means of protecting themselves against the AIDS virus. That's why a vaginal microbicide -- an agent that kills HIV without harming the vagina -- is one of the Holy Grails of AIDS research.
So far, the gel's only been tested in monkeys. But the results are very encouraging. The gel protects monkeys against a much higher concentration of viruses than would be found in HIV-infected human semen.
"Robust protection is encouraging for the development of a microbicide for women," writes researchers Ronald S. Veazey, DVM, PhD, of Tulane National Primate Research Center in Covington, La., and colleagues.
The Veazey team reports the findings in the Nov. 3 issue of Nature.
Three-Drug Combo Gel
The gel uses three drugs originally developed as oral anti-HIV drugs. The first two drugs attach to cells. They block the docking molecules HIV must use to infect a cell. The third, a modified version of the AIDS drug sold as Fuzeon, keeps HIV from fusing to cell membranes.
Veazey and colleagues tested each of the drugs separately and in pairs, but they found that the three-drug combination worked best in protecting macaque monkeys from a hybrid monkey/human AIDS virus.
They also found that the gel protected monkeys for six hours after application.
The researchers note that all three drugs were developed as oral agents. Modifications to the drugs, they say, are likely to increase their anti-HIV effect in the vagina.
Expense May Not Be An Issue
Most AIDS drugs are very expensive. But the small molecules used in the gel are not particularly expensive to make. Pharmaceutical giants Merck and Bristol-Myers Squibb own the compounds. They've already granted full rights for a nonprofit organization to develop and distribute the gel.
That's important because only widespread use of an effective HIV vaginal microbicide can have an impact on the AIDS pandemic.
Human clinical trials are expected to start in 2007. Until then, it's too soon to say whether the gel will work. An earlier vaginal microbicide, Nonoxynol-9, turned out to irritate the vagina. Instead of protecting women, it actually made them more vulnerable to HIV infection.
Cornell University researcher John P. Moore, PhD, one of the study researchers, urges cautious optimism.
"This is encouraging for the development of a microbicide for use in the real world," Moore said in a news release. "Animal studies are an important step, but there is much more work that needs to be done before a product can be made available for human use. Small clinical trials to determine safety and optimal dosage will be the next stage."
At least five other experimental vaginal microbicides are being tested in humans.
Sources: Veazey, R.S. Nature, Nov. 3, 2005; vol 438: pp 99-102. News release, Nature. News release, National Institute of Allergy and Infectious Diseases. News release, Tulane University.
By Daniel J. DeNoon
Reviewed by Louise Chang, MD
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