[Aug 04, 2008]

      By the middle of next year, more people from around the world will be enrolled in trials to test pre-exposure prophylaxis as an HIV prevention method than in trials for HIV vaccine candidates or microbicides, according to a report released Sunday by the AIDS Vaccine Advocacy Coalition at the opening of the XVII International AIDS Conference in Mexico City, the New York Times reports. After "bleak findings" from trials testing other HIV prevention methods, including microbicides and HIV vaccines, many HIV/AIDS experts have said that PrEP is the most promising research in HIV prevention, the Times reports.

Initial findings from the trials could be available as early as next year. The trials are testing whether the antiretroviral tenofovir can be used alone or in combination with the antiretroviral emtricitabine to prevent HIV transmission. The trials also aim to establish whether it is safe for HIV-negative people to take the drugs and what effect PrEP has on people who contract HIV while taking the drugs.

Up to 15,000 people -- including men who have sex with men; heterosexual men and women; and discordant couples, in which one partner is HIV-positive and the other is HIV-negative -- in Botswana, Brazil, Ecuador, Kenya, Malawi, Peru, South Africa, Tanzania, Thailand, Uganda and the U.S. are expected to be enrolled in the trials by mid-2009. USAID, CDC and NIH are providing partial funding for all of the trials, while the Bill & Melinda Gates Foundation is providing support for two of the trials, the Times reports.

According to AVAC, even if PrEP is proven successful, it will need to be combined with other prevention measures, including safer sex practices and use of clean needles.

In addition, the findings are likely to raise additional questions, such as whether taking PrEP just before sexual contact can be effective in preventing HIV transmission, the report said (Altman, New York Times, 8/4).

The report also identifies five priority issues for PrEP:

• Ensuring that current trials have the best chance of producing data to determine the next steps;
  
  
• Identifying and investing in additional research on PrEP;
  
  
• Planning for optimal use of PrEP;
  
  
• Preparing for global procurement and delivery of PrEP; and
  
  
• Providing adequate funding (AVAC release, 8/3).
  

"We cannot wait for the study results to begin to prepare for the optimal use and delivery of PrEP," Pedro Goicochea, an investigator for a PrEP study in Ecuador and Peru, said. He added, "Instead we should look ahead to consider all of the possible outcomes of these trials and make real plans for making PrEP available to those who can benefit from it as quickly and safely as possible if it is proven effective" (New York Times, 8/4).

AVAC Executive Director Mitchell Warren added that the HIV/AIDS research community "cannot shy away from discussing issues such as potential drug resistance, the difficulty of adhering to a once-a-day pill regimen for people who are [HIV-negative] or the cost of providing PrEP," adding that the report "lay[s] the groundwork for these important discussions" (AVAC release, 8/3).

The report is available online (.pdf).

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