Tenofovir was approved by the U.S. Food and

Tenofovir was approved by the U.S. Food and Drug Administration in 2001 as a treatment for HIV infection, and the tenofovir plus emtricitabine combination pill was approved for use as an HIV treatment in 2004. Data from Gilead Sciences, Inc., the manufacturer of the drugs, indicate that more than one million HIV-infected people around the world have now used these drugs. As treatments for HIV-infected individuals, tenofovir and tenofovir plus emtricitabine have been shown to be both safe and effective. They have relatively low levels of side effects and slow development of associated drug resistance, compared with other available HIV treatments. Because the therapies are taken orally only once a day, with or without food, they are also among the most convenient-to-use HIV drugs available today. CDC’s PrEP trials are designed to evaluate the drugs’ safety and efficacy among HIV-uninfected individuals. Side effects may differ in HIV-negative populations, and it is not yet known if tenofovir or tenofovir plus emtricitabine can prevent HIV infection in humans.

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CDC-Sponsored PrEP Trials

Specific Trial Designs and Objectives

Both of CDC’s current studies are randomized, double-blind, placebo-controlled trials. All participants receive risk-reduction counseling and other prevention services. In addition, half of the participants are randomly assigned to receive one antiretroviral pill daily (either tenofovir or tenofovir plus emtricitabine, depending on the trial), and the other half are randomly assigned to take one daily placebo pill (a similar tablet without active medication). Neither researchers nor participants know an individual’s group assignment. In all, the studies involve approximately 3,600 volunteers. The Thailand trial of tenofovir began in 2005 and the Botswana trial of tenofovir plus emtricitabine began in early 2007. Results are anticipated within the next year

To ensure that the studies remain on a solid scientific and ethical foundation, all study procedures and plans are reviewed and approved by scientific and ethical review committees at CDC (called institutional review boards, or IRBs), as well as IRBs established by each host country and research site prior to trial launch. Additionally, data on safety, enrollment, and efficacy are reviewed regularly by an independent data safety and monitoring board (DSMB) for each trial. The boards review emerging data to ensure that continuing the trial is safe and to determine the point at which the results are conclusive. If scientific questions arise during the course of the research, the boards meet more frequently.