The International AIDS Vaccine Initiative (IAVI) welcomes news of the positive results of the Partners PrEP study, a multinational clinical study evaluating the daily use of oral antiretroviral drugs to prevent HIV acquisition, a strategy known as pre-exposure prophylaxis (PrEP). Partners PrEP involved 4,758 heterosexual HIV discordant couples, in which one partner is HIV positive, while the other is not. Researchers evaluated the ability of daily oral regimens of antiretroviral medications, tenofovir or a combination of emtricitabine and tenofovir, to prevent HIV transmission when given to the HIV negative partner. The approach proved highly effective in this population. So much so that the study’s independent Data and Safety Monitoring Board, following a review of the efficacy data on July 10, 2011, recommended that the placebo arm of the study be immediately halted and the results made public.
The group that received tenofovir had an average of 62% fewer HIV infections and those who received the drug combination had 73% fewer HIV infections than those who received placebo. The differences between the two regimens are not statistically significant, and both regimens appear to be similarly effective in preventing HIV transmission in men and women in HIV discordant relationships. The drug regimens were safe and well tolerated, and the study authors reported that adherence to the placebo and the drugs were equally high (>97%). The researchers plan to continue the other two arms of the study to better compare and evaluate the two drug regimens.
Partners PrEP is led by researchers at the University of Washington’s International Clinical Research Center and conducted at nine sites in Kenya and Uganda. Its findings were echoed in results released today of a study conducted by the BOTUSA Project in Botswana, a collaborative effort of the US Centers for Disease Control and Prevention and the Government of Botswana. BOTUSA found that the combination of tenofovir and emtricitabine reduced the risk of acquiring HIV by roughly 63% in heterosexual men and women in the study population.
The preliminary results of these two PrEP studies reinforce those of another international study, known as iPrEX, which evaluated the strategy in men and transgendered women who have sex with men. Together, these findings support the potential for PrEP to prevent HIV in a variety of populations when provided within the context of a complete HIV prevention package that includes HIV counseling and testing and the promotion of condom use. IAVI, which has conducted its own small PrEP studies, supports a comprehensive response to the HIV pandemic that expands such measures while redoubling efforts to develop novel biomedical tools, such as a vaccine, to curtail HIV transmission.
IAVI extends its heartiest congratulations to the team at the University of Washington’s International Clinical Research Center, their colleagues in Kenya and Uganda, the Bill & Melinda Gates Foundation, which funded the Partners PrEP study, and Gilead Sciences, which provided the antiretrovirals used in this vitally important study. It also congratulates the researchers of the BOTUSA Project on their latest results and looks forward to more positive news from both these studies.