Other agencies are also conducting PrEP trials. In 2006,

Other agencies are also conducting PrEP trials. In 2006, Family Health International (FHI), with funding from the Bill & Melinda Gates Foundation, completed a safety trial of tenofovir for HIV prevention among young women in Ghana, Nigeria, and Cameroon. The study provided the first data showing PrEP with tenofovir to be both safe and acceptable for use by HIV-negative women. The National Institutes of Health is currently evaluating the safety and efficacy of PrEP among MSM in Peru, Ecuador, South Africa, Brazil, Thailand, and the United States, and additional trials investigating PrEP among women have been launched in Africa. A full list of current trials, researchers, and sponsors is available from AVAC: Global Advocacy for HIV Prevention.

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Rationale for Trials of Pre-Exposure Prophylaxis for HIV Prevention

Researchers believe that an antiretroviral drug taken as a daily oral preventative treatment is one of the most important new HIV prevention approaches being investigated today. An effective daily preventative treatment could help address the urgent need for female-controlled prevention methods and, when combined with existing prevention measures, could help reduce new HIV infections among men and women at high risk.

Characteristics of Current PrEP Candidates

• Established safety as HIV treatments
• Potent antiretrovirals
• Long duration of action
• Once-daily dosing
• Low levels of resistance

The concept of providing a preventative treatment before exposure to an infectious agent is not new. For example, when individuals travel to an area where malaria is common, they are advised to take medication to fight malaria before and during travel to that region. The medicine to prevent illness will then be in their bloodstream if they are exposed to the infectious agent that causes malaria.

Several sources of data suggest that the use of antiretroviral drugs in this manner may be effective in reducing the risk of HIV infection. Theoretically, if HIV replication can be inhibited from the very first moment the virus enters the body, it may not be able to establish a permanent infection. Providing antiretrovirals (ARVs) to HIV-infected women during labor and delivery and to their newborns immediately following birth has been shown to reduce the risk of mother-to-child transmission by about 50 percent.

Additionally, in observational studies, ARV regimens have been associated with an 80 percent reduction in the risk of HIV infection among health care workers following needle sticks and other accidental exposures, when treatment is initiated promptly and continued for several weeks. Finally, animal studies have shown that tenofovir can reduce the transmission of a virus similar to HIV in monkeys when given before and immediately after a single retroviral exposure. Animal studies have also demonstrated that pre-exposure administration of tenofovir plus emtricitabine provided significant protection to monkeys exposed repeatedly to an HIV-like virus. These data, combined with the drugs’ favorable resistance and safety profiles as HIV treatments, make tenofovir and tenofovir plus emtricitabine good choices for HIV prevention trials.