Preventative treatment dramatically reduces HIV risk in gay men

(Adds details of second PrEP study, UNAIDS comments)

By Kate Kelland

LONDON, Feb 24 (Reuters) - Gay men at high risk of HIV who took a daily dose of a Gilead AIDS drug as a preventative measure cut their risk of infection by 86 percent, according to results of a British trial released on Tuesday.

Researchers who conducted the trial of so-called pre-exposure prophylaxis (PrEP) said the results offer real hope of reversing the HIV epidemic among men who have sex with men, one of the highest risk groups.

"These results ... show PrEP is highly effective at preventing HIV infection in the real world," said Sheena McCormack, a professor of clinical epidemiology at University College London and the study's lead investigator.

PrEP involves people who do not have HIV but who are at high risk of becoming infected and seek to protect themselves by taking a single pill, usually a combination of two antiretrovirals, every day.

Some 35.3 million people worldwide have HIV. AIDS experts estimate that globally, new HIV infections among gay men could by reduced by 20 to 25 percent through PrEP -- averting up to a million new infections in this group over 10 years.

The drug used in the UK trial -- Gilead's anti-retroviral Truvada -- was known to reduce new HIV infections in placebo-controlled trials, but researchers wanted to see if similar success could be achieved in a "real world" context.

Some 545 men were enrolled at 13 sexual health clinics across England and randomised to receive PrEP immediately or after a period of 12 months, allowing researchers to compare those on PrEP versus those not yet on PrEP.

The results, presented on Tuesday at the Conference on Retroviruses and Opportunistic Infections (CROI) in Seattle in the United States, showed there were 22 HIV infections among participants in the first year -- three in the immediate group and 19 in the deferred group.

The researchers said the 86 percent protection is the best reported from a randomised controlled PrEP trial to date.

In a second PrEP trial also presented at CROI, French researchers enrolled 450 high-risk gay men and gave half a placebo and asked the others to take four tablets of the AIDS drugs tenofovir and emtricitabine, two before and two after sex.

Their results showed men in the active pill group were also 86 percent less likely to become infected with HIV.

Michel Sidibe, executive director of the United Nations AIDS agency UNAIDS said these "timely and important" findings would "advance global efforts to end the AIDS epidemic by 2030".

"These new results are a significant breakthrough in advancing efforts to provide effective HIV prevention options," he said in a statement. (Editing by Catherine Evans)