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Treatment or prevention?

When AIDS was first described in the medical literature 25 years ago, there was not a single medicine to treat people infected with this new human virus. Since then more than 20 antiretrovirals (ARVs) have been licensed by the US Food and Drug Administration for the treatment of HIV/AIDS. These drugs have dramatically improved the health of millions of HIV-infected people around the globe and are now becoming increasingly available in developing countries where the need is still the greatest. But with 4.9 million new HIV infections last year alone, new ways to stem the spread of HIV are more urgent than ever. In response researchers have turned their attention to novel approaches to HIV prevention. One of these involves giving the ARVs usually used to treat HIV infection to try to protect people from contracting the virus in the first place. The idea of healthy people popping pills to stay HIV free may seem strange, but it isn’t without precedent. Travelers headed to countries where malaria is endemic will often take drugs to protect them from becoming infected with this parasitic disease. Researchers hope that giving ARVs to individuals at high risk of HIV infection could have the same effect. This idea is known as pre-exposure prophylaxis, or PrEP, and is being tested in five ongoing clinical trials. “We urgently need new types of prevention tools and PrEP is one of many promising strategies, like microbicides and vaccines,” says Albert Liu, an investigator for one of the PrEP trials in the US. Researchers first thought that PrEP might be an effective approach more than a decade ago but the complexities of conducting clinical trials to test the idea has placed them at the forefront of debate. Many researchers harbor concerns that giving drugs that are known to be effective for treating the disease could encourage people to participate in more risk behavior, an idea known as behavioral disinhibition, which could lead to a higher risk of infection. But investigators involved in clinical trials insist that measures are in place to limit this effect. And if found effective PrEP may have the greatest benefit for people who are unable to negotiate use of traditional barrier methods and therefore have few options when it comes to HIV prevention. “We desperately need PrEP to protect women in resource-poor settings,” says Joep Lange of the University of Amsterdam. If the idea of PrEP is borne out in clinical trials, many other questions may arise about implementing this strategy on a global basis. Researchers will confront issues of long-term drug toxicity when ARVs are taken outside the controlled environment of a clinical trial. Other issues like drug pricing and the community outreach and educational campaigns needed to introduce this concept to communities may present further obstacles. “PrEP is not a universal panacea,” says Lange, who emphasizes that an AIDS vaccine is “still an absolute priority” since its impact will be far greater.