CDC Provides Interim Guidance on HIV Preexposure Prophylaxis

Emma Hitt, PhD

January 27, 2011

January 27, 2010 — Interim guidance for preexposure prophylaxis (PrEP) for the prevention of HIV infection in men who have sex with men (MSM) has been issued by the US Centers for Disease Control and Prevention (CDC), based on phase 3 trial results.

Findings from the placebo-controlled randomized Pre-Exposure Prophylaxis Initiative (iPreEX) study reported in November 2010 indicated that 300 mg tenofovir disoproxil fumarate and 200 mg emtricitabine (Truvada, Gilead Sciences), when taken once daily in a combined oral formulation, is safe and partially effective in reducing the acquisition of HIV infection among uninfected but exposed MSM.

The study findings, published online November 23, 2010, in the New England Journal of Medicine, were previously reported by Medscape Medical News.

Dawn K. Smith, MD, and colleagues from the CDC's National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention in Atlanta, Georgia, described these results and the interim guidance in the January 28 issue of the CDC's Morbidity and Mortality Weekly Report.

The multinational trial including 2499 enrolled participants found that enrollment in the PrEP group was associated with a 44% reduction in HIV acquisition (95% confidence interval [CI], 15% - 63%) compared with the placebo group, with increasing risk reduction associated with greater adherence to prophylaxis.

"For MSM whose behaviors place them at high risk for HIV infection and who do not use other effective prevention methods consistently, PrEP might reduce their risk for HIV infection," Dr. Smith and colleagues write. "Until comprehensive US Public Health Service guidelines are available, CDC is providing interim guidance to help guide clinical practice," they add.

The interim guidance provides direction for initiating, prescribing, and discontinuing PrEP. Guidelines suggest that eligible patients should be confirmed as HIV-negative and at "substantial, ongoing, high risk for acquiring HIV infection." In addition, no more than a 90-day supply should be provided, and risk reduction, adherence counseling, and condoms should accompany antiretroviral therapy. Follow-up HIV testing should be provided every 2 to 3 months. PrEP can be discontinued at patient request, for safety reasons, or if the patient becomes infected with HIV.

Dr. Smith and colleagues note that concerns that warrant further study include the fact that "without early guidance, various unsafe and potentially less effective PrEP-related practices could develop among health-care providers and MSM beginning to use PrEP in the coming weeks and months." These include using antiretroviral drugs that have not been proven safe, not screening before or during PrEP at adequate intervals, and failing to provide other HIV prevention support.

"Completing the guidelines and obtaining expert input and public comment will take several months before they can be published," the authors note.

"The study shows a protective effect and already people are asking for PrEP, so therefore objective guidelines will be useful to clinicians," said independent commentator Paul E. Sax, MD, Clinical Director of the HIV Program and Division of Infectious Diseases at Brigham and Women's Hospital and Associate Professor of Medicine at Harvard Medical School. However, he pointed out that this is a "very new area and there needs to be close follow-up of people who are prescribed PrEP, because obviously the intervention is not 100% effective."

Dr. Sax also emphasized that PrEP is only for high-risk individuals. "PrEP is not for someone who is at 'community' risk, meaning the general population," he told Medscape Medical News in a phone interview. "This would be, at least in the United States, for MSM who are not reliably using protection."

According to Dr. Sax, no data yet support the idea that PrEP would have a disinhibitory effect on sexual behaviors that would increase exposure risk; however, he pointed out that antiretroviral therapy makes infected individuals less contagious and has not been shown to have a disinhibitory effect.

"There is an interest in using other regimens," Dr. Sax said, "although nothing yet has been proven." He added that the CCR5-blocker maraviroc might be useful for this purpose since it acts to prevent viral entry into cells. "But I would advocate against using nontested PrEP because the efficacy and safety are as yet unknown."

Figure 1.
Figure 1.
 

The author has disclosed no relevant financial relationships, and the study was not commercially funded. Paul E. Sax, MD, has disclosed the following relevant financial relationships: Served as an advisor or consultant for: Abbott Laboratories; Bristol-Myers Squibb Company; Gilead Sciences, Inc.; GlaxoSmithKline; Merck & Co., Inc; Pfizer, Inc.; Tibotec, Inc. Received grants for clinical research from: GlaxoSmithKline; Merck & Co., Inc.; Tibotec, Inc.

Morb Mortal Wkly Rep. 2011;60:65-68. Full text

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