A daily dose of an oral antiretroviral drug, currently approved to treat HIV infection, reduced the risk of acquiring HIV infection by 43.8 per cent among men who have sex with men. The findings, a major advance in HIV prevention research, come from a large international clinical trial published online 23 November by the New England Journal of Medicine. The study, titled ‘Chemoprophylaxis for HIV Prevention in Men,’ found even higher rates of effectiveness, up to 72.8 per cent, among those participants who adhered most closely to the daily drug regimen.
"We now have strong evidence that pre-exposure prophylaxis with an antiretroviral drug, a strategy widely referred to as PrEP, can reduce the risk of HIV acquisition among men who have sex with men, a segment of the population disproportionately affected by HIV/AIDS," says Anthony S. Fauci, MD, director of the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health. "Additional research is needed, but certainly this is an important finding that provides the basis for further investigating, developing and employing this prevention strategy, which has the potential to make a significant impact in the fight against HIV/AIDS."
"No single HIV prevention strategy is going to be effective for everyone," adds Dr Fauci, "and it is important to note that the new findings pertain only to the effectiveness of PrEP among men who have sex with men and cannot at this point be extrapolated to other populations. Therefore, we must continue to conduct PrEP research among other study populations, such as women and heterosexual men, to provide a comprehensive picture of its potential utility as an HIV prevention tool."
NIAID sponsored the study, also known as iPrEx, through a grant to the J. David Gladstone Institutes, a non-profit independent research organization affiliated with the University of California at San Francisco. Additional study funding was provided by the Bill & Melinda Gates Foundation. Gilead Sciences, based in Foster City, Calif., donated the study drug.
Led by study chair Robert M. Grant, MD, of the Gladstone Institute of Virology and Immunology, and study co-chair Javier R. Lama, MD, of Investigaciones Medicas en Salud, a Peruvian-based research organisation, the iPrEx study enrolled a total of 2,499 men who have sex with men and transgendered women who have sex with men. All participants were at least 18 years old and HIV-negative at time of enrolment. The study, which began in June 2007, was conducted at 11 sites in Brazil, Ecuador, Peru, South Africa, Thailand and the United States.
The study participants were randomly assigned to receive either a daily antiretroviral tablet containing combination emtricitabine (FTC 200 milligrams) and tenofovir (TDF 300 milligrams), or a placebo pill. Before enrolment, all participants received detailed information about the possible risks and benefits of participating in the trial. Once enrolled, they were evaluated for HIV infection monthly for the duration of their participation in the study. The average enrolment was 1.2 years. In addition, all participants were routinely counselled about safe sex practices and provided condoms and treatment for other sexually transmitted infections.
In the final analysis, 100 cases of HIV infection occurred among participants in the iPrEx study. Of those, 36 HIV infections occurred among the 1,251 participants who received the antiretroviral therapy compared with 64 HIV infections among the 1,248 participants who received the placebo. This level of effectiveness in reducing the risk of HIV infection, 43.8 per cent, is statistically significant. Furthermore, the drug’s ability to reduce the risk of HIV acquisition was greater among those volunteers who were more adherent to the daily drug regimen. Participants who took the drug on 50 per cent or more days as measured by pill count, bottle count and self reporting experienced 50.2 per cent fewer HIV infections. Those who took the drug on 90 per cent or more days had 72.8 per cent fewer HIV infections.
The researchers concluded that consistent with earlier, smaller studies leading up to this trial, tenofovir appeared to be safe and well-tolerated for its use in the iPrEx study. Side effects were mild and infrequent and included a small number of participants with transient nausea and mild elevations in creatinine, a naturally occurring molecule filtered by the kidneys. These elevations resolved spontaneously or with discontinuation of the drug. Additionally, very little drug resistance occurred with no instances of tenofovir resistance and three cases of emtricitabine resistance (one participant in the placebo group; two participants in the active drug group). The two cases of emtricitabine in the active drug group occurred among individuals who were in the stages of acute HIV infection at the time of enrolment, but who tested negative for HIV. Both groups of study participants reported a decrease in the number of sexual partners and increased condom use.
"The iPrEx study provides important evidence that PrEP works to reduce HIV infection risk among gay and bisexual men," says Dr Grant. "The need for new HIV prevention methods is critical. PrEP, in combination with other prevention methods, such as HIV testing, counselling and consistent condom use, could represent a major step forward for efforts to control the global epidemic."
Correct and consistent condom use and a reduced number of sexual partners remain the most effective ways for gay and bisexual men to protect against HIV infection.
"A variety of expert and community advisory groups at the federal, state and local levels are looking closely at the study data and will move forward in a deliberative and measured way over the coming months to determine whether and how these findings should be incorporated into ongoing HIV prevention programs," says Howard K. Koh, MD, assistant secretary for health at the US Department of Health and Human Services.