July 13, 2011

PrEP Reduces HIV Risk in Two Major Studies

Two African studies of pre-exposure prophylaxis (PrEP) provide additional evidence that antiretroviral (ARV) drugs can be used to prevent HIV transmission, according to early results from both clinical trials, released ahead of their full presentations at the 6th International AIDS Society Conference of HIV Pathogenesis, Treatment and Prevention next week in Rome.

Unlike the encouraging results from the iPrEx study, reported in November 2010 and enrolled men who have sex with men and transsexual women, the Partners PrEP study and TDF2 study focused on heterosexual men and women at risk of HIV Infection. 

“This is an extremely exciting finding for the field of HIV prevention,” said Jared Baeten, MD, of the University of Washington and a lead investigators of the Partners PrEP study, conducted in Kenya and Uganda. “Now, more than ever, the priority for HIV prevention research must be on how to deliver successful prevention strategies, like PrEP, to populations in greatest need.” 

“Our biggest challenge now is how do we move from research to getting things out to the general public where they’re most needed,” said Lynn Paxton, PhD, of the U.S. Centers of Disease Control and Prevention (CDC), according to the Washington Post. Paxton was a lead investigator of the TDF2 clinical trial, conducted in Francistown and Gaborne, Botswana.

The Partners PrEP study in enrolled 4,758 heterosexual couples in which one partner was HIV-positive and the other HIV-negative. The study was discontinued 18 months early, in light of an interim review suggesting favorable results.

The trial showed that both tenofovir (sold as Viread) and tenofovir plus emtricitabine (sold as Truvada), taken once daily by the uninfected partner, reduced the risk of HIV transmission by 62 percent and 73 percent, respectively, when compared to a placebo. The reported risk reductions were highly statistically significant, meaning they were too great to have occurred by chance, and both drugs were effective in both men and women.

A total of 78 infection were reported by the researchers: 18 in the Viread group, 13 in the Truvada group and 47 in the placebo group. The relatively low number of infections all three groups, given the size of the study, can partly be explained by the provision of HIV transmission counseling and condoms provided to all clinical trial participants.  

The study authors also noted remarkably high adherence rates. More than 97 percent of the prescribed doses were taken correctly and 95 percent of those who entered the study remained in the trial.

No significant safety problems were reported by the researchers.

The TDF2 study enrolled roughly 1,200 sexually active men and women between the ages of 18 and 39. While it was not designed as an efficacy trial—the goal was to look for potential safety problems—the researchers announced that Truvada reduced the risk of HIV infection in both men and women by nearly 63 percent, compared with those who received the placebo.

Interestingly, the results of the Partners PrEP study and TDF2 contrast those of the FEM-PReP study, which failed to demonstrate that Truvada was an effective PrEP strategy among at-risk women in Kenya, Tanzania and South Africa.

Complete results from the Partners PreP and TDF2 studies are to be presented in Rome and will likely be discussed in the context of similar studies, notably iPrEx and FEM-PREP.

Search: HIV, prep, pre-exposure prophylaxis, tenofovir, Viread, emtricitabine, Truvada, Partners PrEP, TDF2, Baeten, Paxton, Kenya, Uganda, Botswana, iprex, fem-prep, Africa, heterosexual

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Previous Comments:

Frederick Wright, Souther California, 2011-07-20 14:02:33
Anthony, I hope you can understand that if 60 percent of new cases can be diverted form AIDS than this alone could stop millions of women and men from having HIV until they understand committed relationships. If your country had half the new HIV cases a year is that not a blessing. And if you add the microbocite gell with the treatment it up the odds to 100 percent. The 60 percent to me is about the same chances of staying alive on ARV, if your HIV. Come on man hope and progress.

Anthony, Kampala, 2011-07-13 14:24:26
I somehow do not see why anyone would be excited by a 63% reduction in the chance of catching HIV.

When interpreted in another way,this means someone on Truvada as PREP takes a 37% chance at getting infected,not good odds

Frederick Wright, Southern California, 2011-07-13 10:48:27
I have been self titrating Atripla for sometime , first weekends off, every other week, then furhter out and furuther out. When I start to feel low on energy and other self factors,then I go back on Atripla as avaiable. The point is on my last rotation of titration a month off, I had labs scheudale and started back on Atripla 3 days before labs and was amazed to have a undectectable virial load. Which tells me that Atripla works very fast or in this limited self study has a lenthie cycle in me.