Can a Pill a Day Prevent HIV?

Congressional Briefing Tackles Implications of PrEP

December 17, 2008—What if those most at risk for HIV could take a pill that would reduce the risk of infection? amfAR’s Public Policy office brought together a panel of experts to discuss the implications of just such a scenario at a recent Congressional briefing in Washington, D.C., December 4.

“We are fighting an uphill battle, and we must vigorously pursue new strategies,” said Dr. Richard Wolitski, acting director of the HIV/AIDS Prevention Division of the Centers for Disease Control and Prevention. For every person on antiretroviral therapy, 2.5 people are newly infected with HIV. According to Dr. Wolitski, every day there are 7,400 new infections worldwide; in the U.S., there is a new HIV infection every 9.5 minutes.

“At this point in time, we do not have the resources to bring this epidemic under control,” said panelist Dr. Carl Dieffenbach, director of the Division of AIDS at the National Institute of Allergy and Infectious Diseases at the National Institutes of Health. “Therefore we must turn to novel prevention strategies,” such as pre-exposure prophylaxis, or PrEP.

The experimental technique involves administering anti-HIV drugs before possible exposure to HIV in the hope that they will lower the chances of infection among those at high risk—a proposition currently being tested in ongoing clinical trials. These trials, which are funded by the Centers for Disease Control and Prevention (CDC),  the National Institutes of Health (NIH), USAID, the Gates Foundation, and others, are taking place in Botswana, Brazil, Ecuador, Peru, South Africa, Thailand, and the U.S. Initial results are expected within the next 12 to 18 months.

While the viability of PrEP is unclear, the concept is not an unusual one: people use statins to prevent heart disease, tamoxifen to prevent breast cancer in high-risk individuals, and birth control to prevent unwanted pregnancy. And in the field of HIV healthcare, “Antiretrovirals have drastically reduced mother-to-child transmission. So can these drugs now be used to prevent HIV in high-risk populations?” asked amfAR Senior Policy and Medical Advisor Dr. Susan J. Blumenthal, M.D., M.PA., the panel moderator.

Clinical trials are just the first step for PrEP, speakers agreed. And what if PrEP proves to be effective? Because ARVs are already on the market and widely available, it is crucial now to address the issues that will arise should the PrEP trials succeed, said Dr. Thomas Coates, associate director of the UCLA AIDS Institute. “How do we prepare our prevention systems to deliver this prevention strategy to those populations that need it the most?,” he asked.

Others followed his inquiry with a range of questions: How much will the drugs for PrEP cost and who will pay for them, particularly during a time of economic crisis? Would funding for PrEP siphon support from existing prevention budgets, cutting into proven methods such as syringe exchange or condom distribution? Who should be targeted and how will we identify those at risk? How will adherence to medication be affected by the fact that prevention is the goal rather than treatment?

Adherence also raises other complicated issues. As the PrEP trials unfold, doctors are learning more about which dosing schedules are appropriate to prevent infection and minimize the development of drug resistance. Kevin Cranston, director of the HIV/AIDS Bureau of the Massachusetts Department of Public Health, warned against so-called “disco dosing,” which involves individuals taking a dose of antiretrovirals prior to engaging in possible high-risk behaviors. This sporadic dosing is ineffective and dangerous, he noted, and may cause later problems with drug resistance among those who do contract HIV.

Despite the promise of PrEP, panelists agreed that its greatest benefit would probably be as part of what Dr. Dieffenbach called a “comprehensive HIV prevention tool box”—which already includes HIV testing, condoms, partner reduction, syringe exchange and methadone treatment, circumcision, antiretroviral therapy, and prevention of mother-to-child transmission.

At this point, researchers are keeping a close eye on not only the progress of the PrEP clinical trials but also the possible ethical and financial considerations of this potential prevention tool. Visit www.amfar.org for continuing updates when the results of these trials are published. 

In addition to Drs. Dieffenbach, Wolitski, and Coates, and Mr. Cranston, panelists included amfAR CEO Kevin Robert Frost and Dr. Robert Grant of the University of California, San Francisco.