HIV Prevention
Preexposure Chemoprophylaxis for HIV Prevention in Men Who Have Sex with Men
A total of 2.7 million new infections with the human immunodeficiency virus (HIV) were diagnosed worldwide in 2008, according to the Joint United Nations Program on HIV/AIDS (UNAIDS). Combination antiretroviral therapy for patients with HIV infection restores health and may decrease the transmission of the virus to uninfected partners.1 Therapy also decreases mother-to-child transmission.2
Postexposure chemoprophylaxis is recommended after occupational or nonoccupational exposure to HIV-infected fluids.3 The use of such chemoprophylaxis requires that people recognize when they might have been exposed to HIV and that they start therapy within 72 hours. Both challenges are substantial limitations to the use of postexposure chemoprophylaxis.4,5
We selected emtricitabine (FTC) and tenofovir disoproxil fumarate (TDF) combination therapy in a single tablet (FTC–TDF) for evaluation of preexposure prophylaxis because of several favorable characteristics.6 (Details are provided in the introduction in the Supplementary Appendix, available with the full text of this article at NEJM.org.) The protective activity of FTC and TDF has been shown in mice transplanted with human immune cells7 and in nonhuman primates.8-10– In these studies, there were increased levels of efficacy when both agents were used together, as compared with the use of either agent alone. The administration of the drug both before and after exposure was important for maximizing the protective benefit. 11
Daily preexposure prophylaxis with oral TDF had an acceptable side-effect profile in a trial involving West African women.12 A tenofovir 1% vaginal gel reduced HIV infection rates by 39% among women.13 Men and transgender women who have sex with men are disproportionately affected by the global epidemic.14,15 Surveys of such persons in the United States indicate that the current use of preexposure prophylaxis is rare, although the majority would consider such use if evidence of safety and efficacy became available.16,17
In this multinational study, called the Preexposure Prophylaxis Initiative (iPrEx) trial, we aimed to evaluate the safety and efficacy of once-daily oral FTC–TDF as compared with placebo for the prevention of HIV acquisition among men and transgender women who have sex with men.
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