by Mike Andrew -
SGN Staff Writer
A new study by the UW's International Clinical Research Center shows that a daily dose of anti-retroviral medications can help HIV-negative people remain free of HIV infection, researchers said on July 13.
The study, called the Partners PrEP Trial, is the largest to date to investigate the effectiveness of 'pre-exposure prophylaxis' (PrEP), and the most promising.
The study included 4,758 HIV-negative people in Kenya and Uganda, all with HIV-positive partners. It was launched in July 2008.
One-third of HIV-negative participants took a daily tablet of the anti-retroviral drug tenofovir, one-third a combination of tenofovir and emtricitabine, and the rest a placebo.
The group taking tenofovir alone had an average of 62% fewer HIV infections than those taking the placebo, while the group taking the combination of medications had 73% fewer infections than those taking the placebo, researchers said.
'I just saw the results three days ago,' study co-leader Dr. Jared Baeten told SGN by phone on July 13, 'and there's a lot more analysis to be done, but I was surprised by how soon we saw results.'
The study was originally 'projected to be released at the end of 2012,' Baeten said, but 'it was recommended to us to report the results early because of how powerful the findings are.'
'I think our results really reinforce the results of the iPrEX study,' Baeten continued. 'The HIV prevention benefit of PrEP is very high in men adherent to the treatment program, and that's in really good agreement with iPrEx.'
The so-called iPrEx (Iniciativa Profilaxis Preexposicion or Preexposure Prophylaxis Initiative) study, released in November of last year, found that daily treatment with a combination of tenofovir and emtricitabine reduced HIV infection risk among men who have sex with men and Transgender people by an average of 43.8%.
Asked to account for the stunningly higher success rate in the ICRC study, Baeten said that taking the medications consistently, day-in and day-out, was the key to preventing new infections.
'Adherence to PrEP is what determines the success rate,' he said. 'Our people were extraordinarily adherent. They were very motivated to participate and very motivated to adhere to the regimen.'
Researchers doing the iPrEx study indicated that keeping participants on the treatment regimen was one of their greatest challenges.
'We need to test our blood samples to get an objective measurement of adherence,' Baeten added. 'We can see that from the blood samples. That's one area for further analysis.'
'Tremendously exciting' results
'These results are tremendously exciting and confirm that we are at a pivotal period in the AIDS epidemic,' said Mitchell Warren, executive director of AVAC, a non-profit HIV/AIDS policy and advocacy organization.
'Antiretroviral (ARV) drugs for HIV treatment began to turn the tide of the epidemic 15 years ago, and it is clear that also using ARVs for HIV prevention will strengthen our response to AIDS. PrEP, ARV-based microbicides and treatment as prevention are powerful tools to help end the cycle of new infections and end the epidemic,' Warren said.
Dr. Kevin Fenton, director of the Center for Disease Control's National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, said the study results were a milestone in HIV/AIDS prevention.
'It is clear we are not going to find one magic pill to solve the issue of HIV but by combining this approach with others we are beginning to get a better handle on combination packages. There is reason to be excited,' Fenton said.
'We are in a critical moment in HIV prevention research,' said Dr. Robert Grant of UC San Francisco, the iPrEx protocol chair.
'iPrEx provided the first proof of an important new method of HIV prevention that can help slow the global toll of 2.6 million new HIV infections each year. Partners PrEP and the TDF2 study have now expanded that finding by demonstrating the effectiveness of PrEP in heterosexual women and men.'
Other PrEP studies
The Partners PrEP Trial results were apparently confirmed by a separate study conducted by the CDC and also released on July 13.
Named TDF2, it involved 1,200 heterosexual men and women in Botswana and found that 62.6% fewer HIV infections had occurred in participants taking a combination of tenofovir and emtricitabine compared with the placebo group.
In May, a clinical trial financed by the U.S. government found that treating an HIV-positive individual with anti-retroviral drugs can also reduce the risk of HIV transmission to an uninfected partner by as much as 96%.
In April, a PrEP study of 2,000 women subjects in Kenya, Tanzania, and South Africa was abandoned because it was not showing statistically significant results, however. Researchers for Family Health International (FHI), which conducted the study, said that adherence to the treatment program was a major issue.
In 2010, the Centre for the AIDS Programme of Research in South Africa (CAPRISA) found that a vaginal gel containing tenofovir was 39% effective in reducing a woman's HIV risk when used for about three-quarters of sex acts and 54% effective when used more consistently.
To PrEP or not to PrEP?
The iPrEx study sparked controversy when its results were first announced. Some HIV/AIDS prevention groups - AIDS Healthcare Foundation (AHF), for example - argued that focus on PrEP would divert attention from tried-and-true prevention methods like regular condom use.
AHF even went to the expense of buying ads in most major LGBT newspapers warning that consistent condom use was a better preventative than PrEP drugs.
Baeten, on the other hand, told SGN that his study 'showed an unequivocal treatment benefit.'
Baetne said the medications his team tested are readily available in the US. The tenofovir and emtricitabine combination, for example, is currently marketed as a one-pill drug under the trade name Truvada.
'These drugs are available in the U.S. and can be prescribed right now,' he said. 'People should talk to their doctors [about a prescription].'
'There are some issues with insurance coverage,' Baeten added. 'There are really important questions that have to be worked through. But people should advocate for [making PrEP drugs available].'
Baeten added that the treatment regimen his group tested was safe for both HIV-positive and HIV-negative patients.
'For both the medications we tested, we already have a wealth of experience with HIV-positive men. They are very safe for daily use. Our trial also generated a large amount of safety information for HIV-negative men. [The treatment] was very well tolerated and very safe,' he said.
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