Antiretroviral Drugs Reduce Risk for HIV Infection

Laurie Barclay, MD

July 11, 2012

July 11, 2012 — Antiretroviral preexposure prophylaxis (PrEP) may help prevent HIV infection among high-risk individuals, according to a Cochrane systematic review published online July 11 in the Cochrane Database of Systematic Reviews. This review updates a systematic review first published in 2009.

"More than 30 years into the global HIV/AIDS epidemic, infection rates remain alarmingly high, with over 2.7 million people becoming infected every year," write Charles Okwundu, from the Centre for Evidence-Based Health Care at Stellenbosch University in Tygerberg, South Africa, and colleagues. "There is a need for HIV prevention strategies that are more effective. Oral antiretroviral [PrEP] in high-risk individuals may be a reliable tool in preventing the transmission of HIV."

Okwundu and colleagues performed the current review to assess the value of orally administered PrEP in preventing HIV infection among uninfected individuals who are at high risk. In April 2012, the reviewers searched MEDLINE, the Cochrane Central Register of Controlled Trials, and EMBASE for published studies. They also searched the World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov for ongoing trials.

Inclusion criteria for studies were randomized controlled trials evaluating the effects of any antiretroviral drug as monotherapy or in combination for prevention of HIV infection in high-risk individuals. Using a standardized data extraction form, 2 authors independently extracted data regarding outcomes, details of the interventions, and other study characteristics.

Of 12 randomized controlled trials meeting inclusion criteria, 6 were ongoing trials, 4 had been completed, and 2 had been terminated early. Data for this review were collected from 9849 participants enrolled in 6 studies assessing daily oral tenofovir disoproxil fumarate (TDF) plus emtricitabine (FTC) vs placebo, TDF vs placebo, and daily TDF-FTC vs intermittent TDF-FTC. One of these trials compared the effects of TDF, TDF-FTC, and placebo.

The studies enrolled HIV-uninfected men who have sex with men, serodiscordant couples, and other men and women at high risk for HIV infection.

Compared with placebo, TDF-FTC was associated with a 49% reduction in the risk of acquiring HIV infection, based on 4 trials (risk ratio [RR], 0.51; 95% confidence interval [CI], 0.30 - 0.86; 8918 participants). TDF only was associated with a significant 62% reduction vs placebo in the risk of acquiring HIV infection (RR, 0.38; 95% CI, 0.23 - 0.63, 4027 participants).

Across all the studies that reported on adverse events, there were no significant differences observed between the PrEP and control groups. Moreover, the intervention and control groups had similar treatment adherence and reported sexual behaviors.

"Our findings suggest that antiretroviral drugs can reduce the risk of HIV infection for people in high risk groups," Okwundu said in a news release. "However, in the search for highly reliable HIV prevention strategies, it is important to determine how pre-exposure prophylaxis can best be combined with existing programmes, as no strategy is likely to be 100 per cent effective."

Limitations of this review include those inherent in the included studies.

"There are still many questions that need to be answered," Okwundu said. "For example, how do we ensure that people adhere to their [antiretroviral treatment] regimens? What are the long-term effects? Is pre-exposure prophylaxis cost-effective in the long run?"

The study was supported by the Centre for Evidence-Based Health Care at Stellenbosch University, the Nuffield Commonwealth Foundation, and the South African Cochrane Center. Dr. Okwundu and another author were awarded a Reviews for Africa Programme Fellowship funded by the Nuffield Commonwealth Programme through the Nuffield Foundation. The authors have disclosed no relevant financial relationships.

Cochrane Database Syst Rev. Published online July 11, 2012.

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