By Beatrice Jeschek

Scanning electron micrograph of HIV-1 budding (in green) from cultured lymphocyte © CDC

For the first time, a study of gay men has demonstrated that an anti-HIV pill can protect uninfected people from contracting the AIDS virus through sex.

The results were published today in the New England Journal of Medicine.

The results show that an already approved drug, Truvada, can halve transmission rates. This could provide a powerful new tool to curb the AIDS epidemic.

“The end of AIDS is no longer a dream, it’s in sight,” said Mitchell Warren, executive director of the New York-based AIDS Vaccine Advocacy Coalition, quoted in Businessweek. “We have tools that when combined are going to allow us to break the back of the epidemic.”

Robert Grant, a virologist at the University of California, San Francisco (UCSF), headed the study, which involved gay men aged 18 to 67 in Peru, Ecuador, Brazil, the United States, Thailand, and South Africa.

But Grant emphasizes, according to ScienceNOW, that the findings only apply to men and transgender women who have sex with men; other studies are underway to evaluate PrEP in heterosexual men and women and injecting drug users, he said.

The U.S. Centers for Disease Control and Prevention warned in a media statement that condoms remain the best way to avoid infection.

The results

As reported online today in The New England Journal of Medicine, the strategy, called pre-exposure prophylaxis, or PrEP, was tested in 2499 HIV uninfected men and transgender women who have sex with men. Half of the group received a placebo.

In the treatment group, transmission dropped by 44%, despite the fact that many study participants in the trial frequently skipped doses. When the researchers analysed a small subset of people who received the treatment and not the placebo, they found a 72% protection rate in people who took the drug regularly.

Nearly 30 large-scale HIV prevention studies have failed, making these results much more heartening. The new study had cost $43.6 million and was conducted in six countries between July 2007 and December 2009.

Funding

The National Institute of Allergy and Infectious Diseases (NIAID) provided two-thirds of the funding for the study, and the Bill & Melinda Gates Foundation covered the other third.

Trial in South African women

The results come on the heels of a widely celebrated positive finding from a trial in South African women, which this summer reported that a vaginal gel laced with tenofovir reduced infection by 39%. According to experts, this means that antiviral chemo prevention works.

Truvada drug for prescription

The Truvada drug (developed by Gilead Sciences) is a popular anti-HIV treatment, and can be prescribed for "off-label use" by any physician. But it remains unclear whether insurance companies will pay for this off-label use; costs run from $11 per month for a generic version to nearly $1000 per month for the product.

Ethical issues

Researchers caution that no single preventive by itself can stop HIV, which infects people by different routes under a wide variety of conditions. It, however, appears quite clearly that the most potent tools we have right now are drugs.

This article was first published 23/11/2010 on maltastar.com.