An expert panel at the American Foundation for AIDS Research meeting discussed the progress being made developing a user-ready microbicide that would prevent HIV from entering the body through genital surfaces.
"We think there may be a ready-for-use product on the market perhaps sooner than a vaccine and right now, in this epidemic, we need to fight with all the tools we have," said Dr. Polly Harrison, director of the Alliance for Microbicide Development in Silver Spring, Md.
Usually in the form of a gel, foam or cream, microbicides would work in a variety of ways to prevent the HIV transmission. One product in human clinical trials enhances the vagina's natural defenses against HIV using an "acid buffer" compound.
Another alternative is an "absorption inhibitor," which is composed of sulfated and other charged polymers that block the absorption pathways of HIV on the genital surfaces. The most promising of these is a product called Carraguard, a sea weed-based gel in Phase 3 clinical trials.
Canadian researchers at Laval University in Quebec have been developing an "invisible condom" product over the past decade that also appears to block the virus. The condom actually is a non-toxic polymer-based liquid that solidifies into a gel at body temperature and guards against HIV transmission. The gel is entering Phase I clinical trials on female patients and could be on the Canadian market as soon as next year.
While some researchers have focused on creating microbicides, others have concentrated on an equally important issue: Will people actually use the products? Much of that research has centered the attitudes of women, since they are the group most likely to benefit from the products.
Existing strategies for prevention -- mutual monogamy among HIV-negative partners and condom use -- are not options for many women, particularly in developing countries where they do not have the social or economic status to demand condom use.
The microbicide, in contrast, could be used without a woman's partner even being aware of it and one recent study indicated an estimated 21.3 million women in the United States alone would use the products.
"We did find that the a significant number of women who thought that they were at risk for catching a (sexually transmitted disease) STD would be interested in this product," said co-author Jennifer Frost, senior research associate at the Alan Guttmacher Institute in New York City.
A second study by researchers at the Institute for Community Research in Hartford, Conn. showed while women were interested in the products, they were less comfortable using creams and gels than using a male condom. The researchers concluded additional support would be necessary for women to incorporate microbicides into their regular sexual practice.
"We really need to understand people's willingness to use biological means to prevent HIV," agreed Dr. Kenneth Mayer, an AIDS expert at Brown University in Providence, R.I.
At present there are a host of entities involved in microbicide research, including small biopharmaceutical companies, non-profit research groups and public sector entities.
The speed of development has been stalled, however, by a lack of interest on the part of large pharmaceutical companies that are unlikely to see a high return on investment. Instead, private funding from the Bill and Melinda Gates Foundation is largely driving the effort.
"Once somebody's got something that works, there will be more interest," said Dr. Michael J.K. Harper, director of the Global Microbicide Project in Arlington, VA. "But they (the products) have got to be cheap -- comparable to a condom -- because a lot of the market will be in developing countries which can't afford to pay a lot of money for them."