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AIDS fight suffers setback

Researchers halt trials of a promising compound after data show women who used it contracted HIV at a higher rate than those who did not.

February 03, 2007|Daniel Costello | Times Staff Writer

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.

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

But experts say this 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.

Ushercell had proved to be safe and effective in 11 previous smaller trials. Some experts believed that if it was shown to work in larger studies, it could be available to the public by the end of the decade.

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 eventually would be discovered.

Theoretically, the medication, which is applied vaginally or rectally as much as an hour before intercourse, can attack the virus on contact before it leads to infection.

One of the hurdles for faster microbicide research, Forbes said, is that pharmaceutical and biotech companies have largely ignored this area.

But there is evidence that a few larger manufacturers have recently gained at least a cursory interest, adding hope that other good microbicide candidates may be in the pipeline even if the current generation fails to prove effective.

Bristol-Myers Squibb Co. and Merck & Co. have allowed outside researchers to study some compounds that have shown early promise, although the funding for the research has come almost exclusively from governments and nonprofits such as the Gates Foundation, rather than from the industry.

In December, Gilead Sciences Inc. announced it had made an agreement with two nonprofits to develop, manufacture and, if it proves efficacious, arrange for distribution of a possible microbicide.

Not everyone is ready to give up on Ushercell and the other current trials yet.

Dr. Ian McGowan, a professor of medicine at UCLA and a microbicide researcher, said it might be too early to be disappointed by this week's news or conclude that the compound itself 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.

Other anti-AIDS technologies are gaining momentum. Researchers are studying whether women who use a diaphragm during sexual intercourse might reduce their risk of infection. Others are studying whether topical versions of AIDS medications such as Tenofovir might also protect users.

One of the most provocative trials underway is looking to see whether healthy patients who take Tenofovir once a day can protect themselves from infection no matter how the virus is transmitted. The study is being conducted in Atlanta, San Francisco and abroad and is funded partially by the U.S. Centers for Disease Control and Prevention.

Early results on animals have been positive, but researchers have discovered a potentially worrisome development since the trials began two years ago. A black market for the drug among mainly gay clubgoers has developed, in which the drug is sold along with narcotics and Viagra and is typically referred to as "T."


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