in the final analysis, 100 cases of HIV infection

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 percent, 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 percent or more days as measured by pill count, bottle count and self reporting experienced 50.2 percent fewer HIV infections. Those who took the drug on 90 percent or more days had 72.8 percent fewer HIV infections.

The researchers concluded that consistent with earlier, smaller studies leading up to this trial, Truvada 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 enrollment, 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, counseling 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, M.D., assistant secretary for health at the U.S. Department of Health and Human Services.