Study Shows 'On-Demand' PrEP to Drastically Reduce HIV Infection

A new study demonstrates that PrEP, or pre-exposure prophylaxis, will significantly reduce HIV transmission if taken immediately before sex.

Released Wednesday, an update from the French PrEP study ANRS Ipergay, found "a very significant reduction in the risk of HIV infection" when the drug was taken in this manner. The trial was conducted among more than 400 men who have sex with men across seven sites in Montreal and France. ANRS is France's national AIDS research institute.

When the study began in February 2012, volunteers were divided into two pools: a placebo group and one that was given Truvada, a PrEP drug manufactured by Gilead. The participants were directed to take two tablets of "on demand" Truvada at least 24 hours before intercourse, and then a daily pill for the two days following the incident. This regimen was found to be so effective that researchers "unblinded" the study and switched all placebo users to Truvada. More comprehensive data will be released in early 2015.

In the wake of a dramatic HIV spike in gay and bi men, the Center for Disease Control recommends that sexually active gay and bisexual use PrEP, though it cautioned that PrEP "is much less effective if it is not taken consistently." If taken daily, PrEP has been shown to reduce HIV transmission by 99 percent.

This new report cuts against this recommendation, which has also been a central argument of the drug's naysayers, incuding Michael Weinstein, the president of the AIDS Healthcare Foundation. Earlier this year, he called PrEP a "party drug" that would discourage condom use.

However, the study's lead researcher, Jean-Michel Molina, has maintained that these findings are not a reason to abandon condoms as a means of protection, but rather further proof that PrEP is a valuable tool in the kit of HIV prevention.

"The biomedical concept of on-demand PrEP at the time of sexual exposure, in a broader prevention framework, is validated. We owe this to all trial volunteers without whom we could never have achieved these results," Molina said. "We must not forget that condoms remain the cornerstone of HIV prevention. Combining all prevention tools that have proved to be effective will certainly allow us to better control the HIV epidemic."

The director of ANRS, Jean-Francois Delfraissy, added, "This is a major breakthrough in the fight against HIV. The results of the ANRS Ipergay trial should change national and international recommendations for HIV prevention."

The National AIDS Trust, one of the U.K.'s leading HIV organizations, hailed the findings of the study, which could position PrEP as a more cost-effective and practical option of preventing HIV. He said he looks forward to seeing the strategy implemented in a "'real-life' setting.'"

"This announcement from the ANRS Ipergay trial is another exciting piece of news in the growing and powerful evidence base on the effectiveness of PrEP," said Yusef Azad, a director with the organization, in a statement. "It is especially important if it suggests that PrEP might work well when taken only around the time of sex rather than daily -- that could be good news for costs. We will now need to look at how such 'intermittent PrEP' works in a 'real life' setting rather than a placebo-controlled trial."

The ANRS findings mirror those of an ongoing study in Britain, known as the PROUD study, which also found PrEP to be "highly protective" against HIV for gay men, other men who have sex with men, and transgender women, according to a recent interim analysis.

Although the U.S. Food and Drug Administration approved Truvada for use in PrEP over two years ago, PrEP has only recently begun to receive widespread acknowledgement among public figures and organizations for its lifesaving potential. In the past few months, the Centers for Disease Control and Prevention, World Health Organization, Gov. Andrew Cuomo of New York, and the Human Rights Campaign have all come forward in support of PrEP. The Advocate has devoted the month of October to coverage of the prevention strategy in a series titled "31 Days of PrEP."

[RELATED: "35 Activists, Doctors, and Organizaions Speak Out in Support of PrEP"]

"Today, there is an unprecedented chance to end the HIV/AIDS epidemic, in part through PrEP's aggressive prevention of new HIV infections," HRC president Chad Griffin said in endorsing PrEP. "There is no reason -- medical or otherwise -- to discourage individuals from taking control of their sexual health and talking to their doctor about PrEP."