Can the drugs that keep HIV-positive people alive also make it safer to enjoy carefree sex - much as during the pre-AIDS 1970s?
Health officials in the United States, Thailand, Botswana and elsewhere are now trying to find out by conducting trials in which healthy people take drug cocktails that suppress the virus.
“The information that we have indicates that this is a very promising approach,” said the University of California, San Francisco’s Robert Grant, who is overseeing an upcoming study to be conducted in Peru.
“The use of anti-viral drugs for prevention has been evaluated in animal models, especially non-human primates. They have shown to be highly effective in preventing acquisition of viruses that are similar to HIV.”
Researchers have already completed one study in Ghana on the subject, known as Pre-Exposure Prophylaxis (or PrEP), and will present the first findings on the topic next week at the International AIDS conference in Toronto.
To date, the only proven way to prevent AIDS is abstinence or condom use. Yet in recent years researchers have noted a potentially dangerous increase in unprotected sex, including among American gays. Some theorize that the availability of AIDS drugs has made people complacent.
If PrEP works - and it will likely take several years to gain a conclusive answer - “it could stand to save thousands of people from being infected,” said Melanie Thompson, who is leading a PrEP study in Atlanta.
The studies have generated some controversy. Two years ago Cambodia halted a PrEP study, and the African nations of Cameroon and Nigeria pulled out of trials after local protest.
Since the diagnosis of AIDS a quarter century ago, overcoming its risk, for example, by devising a vaccine has proved elusive. The United Nations says 25 million have died since the epidemic emerged.
Yet antiretroviral drugs have kept people with the HIV virus that causes AIDS alive, giving hopes that drugs such as tenofovir (Viread) or the two-drug combination pill Truvada made by the California-based biotech company Gilead Sciences could keep the healthy from getting HIV.
“I would hope that ultimately there is a vaccine. I must say that a preventive vaccine I don’t expect to see in my lifetime,” said Thomas Coates, an expert on HIV prevention at the University of California, Los Angeles. “In the meantime we do need other prevention strategies.”
Even if the approach is shown to work, it may prove very costly. A month’s supply of Truvada at U.S. wholesale prices costs $735.36, Gilead says, although the medication is offered at far lower prices in developing countries.
“The population that might benefit from this is huge,” said Howard Jaffe, the president of the Gilead Foundation.
Yet he said the company would not market the drug as a prophylactic, out of concern about liability, and because insurance companies are unlikely to fund such a use. “It’s likely to be a very charged and complicated issue,” he said.
STRONG NEED IN SAN FRANCISCO
Scientists are studying whether the pills work as an HIV prophylactic and whether they pose any risk to the healthy.
“The concern is, of course, you’re giving potentially toxic medications to people who are otherwise healthy,” said Coates. “I think we have probably a reasonable assurance that the drugs are safe. In terms of effectiveness…that is the million- dollar question.”
Famous for its active gay community, San Francisco earlier this year launched a study on the potential side effects of the medication for the healthy as well as any effects on behavior.
“We urgently need new ways to prevent HIV infection,” said Albert Liu, the study’s director. Anecdotal evidence suggests at least a small number of healthy gay men already take the drugs, hoping for protection before sex - a practice doctors do not endorse.
San Francisco experiences 15-20 new infections a week, and city officials say that just more than a quarter of the city’s estimated 63,577 gay men aged 15 and above are HIV positive.
The study, sponsored by the Centers for Disease Control and Prevention, aimed to have 400 participants in San Francisco and Atlanta, but has struggled to find volunteers. More than 200 are now enrolled.
Medical experts say if the PrEP tests prove effective, those at risk, from prostitutes and drug addicts to those living a sexually risky lifestyle, could take the pills for months or years of their lives. It’s unclear whether funds would be forthcoming to pay for their treatment or if they would adhere to the drug regimen.
Still, medical experts caution that the pills will unlikely prove a free pass to promiscuity.
“We would never recommend that it be used as an excuse or a reason to have unprotected sex,” Liu said. “This approach may not be 100 percent effective .... We would offer it in addition to proven prevention strategies such as, you know, condoms, risk reductions counseling, getting tested frequently.”
Revision date: July 5, 2011
Last revised: by Sebastian Scheller, MD, ScD