The fight to stop the spread of AIDS suffered a serious setback this week when researchers shuttered two high-profile trials of one of the most promising anti-AIDS compounds.
Researchers had hoped that the so-called microbicide, a topical gel designed to block the transmission of the human immunodeficiency virus during sexual intercourse, would be particularly effective in stemming the epidemic of AIDS in Africa and Asia.
The hope is that such products could be especially useful for high-risk populations in developed countries that resist using condoms, as well as for women in the developing world who often can't abstain from sex or insist on condom use.
Unlike current AIDS medications, which treat people already infected with HIV, microbicides would prevent healthy people from being infected.
A successful microbicide could avert nearly a million HIV infections a year, according to a recent Rockefeller Foundation report. The foundation estimates that a dose would sell for about $3 and could become a market worth $2 billion to $5 billion a year.
But researchers announced this week that they had shuttered two trials of the compound because preliminary data found that women using it were contracting HIV at a higher rate than those not using it.
The halt was a setback for Conrad, a Virginia-based health research group that's supported by the Bill & Melinda Gates Foundation, which hoped to market the compound as early as the end of the decade.
It's the second time in recent years that a microbicide appeared to increase the risk of HIV infection rather than retarding it.
In 2000, a large trial found that another high-profile candidate, nonoxynol-9, increased the incidence of HIV infection, potentially from small ulcers caused by chemical irritation.
"This is obviously a huge disappointment at a time we desperately need more options to combat the virus," said Jennifer Kates, director of HIV policy at the Kaiser Family Foundation.
Scientists have been trying to develop an effective microbicide for more than a decade, as other prevention tools have failed to adequately reduce rates of HIV infection in the U.S. and other developed countries. Meanwhile, new infections in the impoverished countries in Africa and Asia continue to explode.
Prevention is considered key because for every person in the world who has access to the current crop of lifesaving AIDS drugs, 10 more people are newly infected.
