Halt of trials a setback in AIDS fight

The fight to stop the spread of AIDS suffered a setback last 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, or HIV, during sexual intercourse, would be particularly effective in stemming the AIDS epidemic in Africa and Asia.

The hope was that such products could be especially useful for high-risk populations in developed countries that resist using condoms and 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 infected with HIV, microbicides would prevent healthy people from being infected.

A successful microbicide could avert nearly 1 million HIV infections a year, according to a recent Rockefeller Foundation report.

But researchers said last week that they had shuttered two trials of the compound because preliminary data found that women using it were contracting HIV, which causes AIDS, at a higher rate than those not using it.

The halt was a setback for Conrad, a Virginia health-research group supported by the Bill & Melinda Gates Foundation, which hoped to market the compound.

It's the second time in recent years that a microbicide appeared to increase the risk of HIV infection rather than retard 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 reduce rates of HIV infection acceptably in the United States 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.

At least three other microbicide candidates are in late-stage trials and one might have results by the end of this year.

But experts say last week's news is particularly disappointing because the microbicide under study in the aborted trials, a compound containing cellulose sulfate and known as Ushercell, was considered the best bet among the current crop.

Anne Forbes, deputy director of the Global Campaign for Microbicides, said Ushercell's apparent failure "could mean we have to tinker a bit with the science or how we're conducting these trials or both." She added that she believed an effective microbicide would be discovered.

Dr. Ian McGowan, a professor of medicine at the University of California, Los Angeles, and a microbicide researcher, said it might be too early to be disappointed by last week's news or conclude that the compound was the reason for the results. It could be that the trial data prove false or that the trial's design, rather than the medication, was flawed, he said.

"We need to let the dust settle here and wait for the researchers to find out what really happened," McGowan said.