Preexposure Chemoprophylaxis Reduces Incidence of HIV Infection in Men who have Sex with Men
Postexposure HIV prophylaxis has been recommended, but the window to start treatment is short (72 hours) and evidence for its efficacy is limited. The Preexposure Prophylaxis Initiative (iPrEx) trial evaluated the safety and efficacy of a 2-drug cocktail for HIV chronic prophylaxis in 2,499 men and transgender women who have sex with men. Participants, who were HIV-negative at baseline, were randomized to a combination of emtricitabine and tenofovir vs. placebo orally once daily and were followed for median 1.2 years. All participants received HIV testing, risk-reduction counseling, condoms, and management of sexually transmitted infections. HIV infection rates were significantly lower in the prophylaxis group (2.9% vs. 5.1%, p = 0.005, NNT 46) (level 1 [likely reliable] evidence). There were no significant differences in overall or serious adverse events or in study drug discontinuation. Of potential concern, chemoprophylaxis was associated with higher rates of unintended weight loss of more than 5% (2.2% vs. 1.1%, p = 0.04, NNH 91). It was also associated with higher rates of nausea (1.6% vs. 0.7%,p = 0.04, NNH 111). In a subgroup analysis of the chemoprophylaxis group, participants with detectable levels of the study drug had decreased risk of HIV infection compared to those without detectable levels (relative risk reduction 92%, 95% CI 70%-99%) (N Engl J Med 2010 Nov 23 early online full-text).
