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New PrEP Study Reinforces Drug's High Effectiveness

PROUD and IPERGAY studies show high effectiveness for PrEP

An ongoing British study, known as PROUD, has boosted confidence that PrEP (pre-exposure prophylaxis) is highly effective at preventing the transmission of HIV. The test, designed to mimic a real-life setting, focussed on two groups pf people, half of them prescribed PrEP at the study's start, in November 2012, and the other half deferred to a later date. Both groups were provided with safe-sex support, condoms, and testing for STIs.

The PROUD study found that those in the deferred arm were much more likely to contract HIV than those taking PrEP, with 8.9 percent contracting the virus, compared to the anticipated 2-3 percent. By contrast, among those taking PrEP the incidence of HIV contraction was 1.3 percent, or three people in total. That translates to a cut of 86 percent in the spread of HIV. The difference was significant enough that last October an independent Data and Safety Monitoring Committee decided it was unethical to withold PrEP any longer from those in the deferred arm.

Even among the three cases in of HIV identified among those taking PrEP from the beginning, one is considered highly likely to have contracted the virus shortly before the study began; the two other infected participants had not attended follow-up appointments. One of those told the clinic that he had not been taking PrEP.

"These results show there is a need for PrEP, and offer hope of reversing the epidemic among men who have sex with men in this country," said Sheena McCormack, chief investigator of the study.

The news is not all good. Thirty of the participants across both groups experienced medical issues, including kidney malfunction in two people, as well as less serious side-effects including headaches, nausea, fatigue, and diarrhea. 

Meanwhile, results from a separate French and Canadian study, Ipergay, presented today at the 2015 CROI Conference in Seattle, had near identical results to the UK study, finding that HIV infection in those taking an intermittent PrEP regime was 86% lower than in people taking a placebo. On Aidsmap.com, Gus Cairns reports that the French study sought to determine whether taking Truvada only around the time that participants were exposed to HIV would also work, as already shown in studies on animals. In the Ipergay study, gay men and transgender women who have sex with men were recommended two Truvada pills from one day to two hours before they planned on having sex, another pill 24 hours later, and a fourth pill 48 hours after sex. Of those on Truvada, two became HIV positive; of those on the placebo the figure was 14. As with the PROUD study, the results were significant enough to offer Truvada to those participants not enrolled in PrEP. And like the UK study, the two men in the PrEP arm who contracted HIV appear to have stopped taking the pills when they became infected, according to the principal investigator, Jean-Michel Molina. 

Writing on Facebook, the veteran ACT UP activist, Peter Staley, heralded the results as a major victory for supporter of PrEP. "Early PrEP adopters will prove to be the heroes of an eventual decline in HIV infections among gay men," he wrote. "They have been scolded and shamed, but are on the right side of science, and the right side of history. The scolds will get very quiet in the years ahead, as they slowly realize how wrong they've been."

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