For more than a decade, researchers have been trying to develop a product that women could use independently to protect themselves against HIV. The results of a three-year study now show that the latest microbicide is not nearly as promising as researchers hoped.
Carraguard, a gel made from a derivative of seaweed, is the first virus-killing microbicide to make it to the final phase of a large-scale clinical study. Since 2004, more than 6,000 South African women participated in the study.
Though Carraguard worked against HIV in the laboratory, the real-world results were disappointing, according to Robin Maguire of the Population Council, which sponsored the study.
"The study did not show that Carraguard was effective," Maguire says.
Some 134 women converted to HIV positive in the Carraguard group compared with 151 in the placebo group, which Maguire says wasn't statistically significant. Part of the problem may have been that there was a great deal of variability in how often women used the gel — only 10 percent of the participants used it consistently every time. Researchers did learn, however, that unlike many prior gels and foams, the product does not increase the risk of HIV, which could be helpful.
"We know that it is safe to be used as a vehicle to deliver another HIV agent. It can be used in combination with something else to make it more potent," Maguire says.
Consequently, the Population Council plans to move ahead with another study that combines Carraguard with an antiretroviral that appears to be effective against the virus in the laboratory, but is not absorbed into the blood stream.
Finding a microbicide that is strong enough to knock out HIV and gentle enough be used every day is a challenge, says Anna Forbes, the deputy director of the Global Campaign for Microbicides.
"It has to be something very compatible with the body as the body blocks the virus from attaching to the cell or to disable the HIV in some other way so it can't take hold and enter the blood stream," she says.
There's one other obstacle that researchers will have to overcome: finding a product that women will use consistently.
"Any of us who have experience using insertive birth-control methods — diaphragm, foam, cervical cap or sponge or putting in condoms — we know a million and one things can get in between your intention to use the product and using the product," Forbes says.
Looking on the bright side, this study proves what many have doubted, she says — that thousands of women in a developing country will hang in for the duration of a large-scale clinical study.