for the first time, a study has shown that anti-HIV pill can protect uninfected people from contracting the AIDS virus through sex. The eagerly awaited results show that a drug already approved can reduce the transmission rate by almost half, which could provide a powerful new tool in the fight against the AIDS epidemic. "It's a game changer," said one of dozens of clinicians who participated in the study, Kenneth Mayer of Fenway Health in Boston. But experts say that the success also raises a dizzying array of complex issues on the human behavior, resources, risks and public health.
the strategy, called pre-exposure prophylaxis, or PrEP, was tested in 2,499 uninfected by HIV and transgender women men who have sex with men. half of the group received a placebo. in the treatment group, the transmission dropped by 44%, despite the fact that many study participants in the trial frequently skipped doses. When researchers analyzed a small subset of individuals who received the treatment, not the placebo, they found an amazing protection rate of 92% among people who had detectable levels of drug in their blood to say, among those who took the drug regularly.
About 30 studies on the prevention of large-scale HIV have failed, making these results that much more encouraging. The new study, called the Prophylaxis Initiative, or iPrEx pre-exposure, cost $ 43.6 million and was conducted in six countries between July 07 and December 09. "The results of the iPrEx study are extremely important and provide solid evidence that PrEP can reduce HIV acquisition among a segment of society that is disproportionately affected by HIV / AIDS, "said Anthony Fauci head of the Institute National allergy and infectious diseases (NIAID) in a conference call for the press held yesterday. NIAID provided two thirds of the funding for the study, and the Bill & Melinda Gates Foundation covered the other third.
as reported online today in the New England Journal of Medicine, the study recruited extremely high risk people to be infected with HIV : participants reported an average of 18 sexual partners in the last 12 weeks, and 60% said they had unprotected receptive anal intercourse in this time. Everyone received regular advice on how to reduce their risk of being infected, as well as condoms and treatment for other sexually transmitted infections. At the end of the trial, 36 of the 1,251 people who received a pill containing a combination of two anti-HIV medicines, tenofovir and emtricatbine (co-formulated as Truvada and made by Gilead of Foster Science City, CA), was infected. Among the 1,248 people who received placebo pills, 64 were infected.
Robert Grant, a virologist at the University of California, San Francisco (UCSF), led the study, which took place in Peru, Ecuador, Brazil, the US, Thailand and South Africa. "I am delighted that we have shown clear evidence that oral Truvada added protection to [men who have sex with men] receive comprehensive prevention," says Grant. "There is a strong result." Although some researchers fear drug resistance could surface or that people might increase their rates of risky behavior because they believed the protection of the drug provided or problem was observed in the study, he said.
But Grant emphasized that the results relate only to men and transgender women who have sex with men; Other studies are underway to evaluate PrEP among heterosexual men and injecting drug users and women.
Many AIDS researchers are not involved in the study said Science they are impressed with its rigor and statistically significant results. But they fear how the strategy will work in the real world. Although participants reported taking the drugs about 0% of the time, the researchers suspect was accurate because drug levels in blood studies. "The questions that remain are more behavioral than biological," said Robert Schooley, a virologist at the University of California at San Diego (UCSD). Grant of UCSF suggests that membership in the plan may have been low because people do not know whether the drug worked or if they received a placebo. Truvada did not cause serious side effects, but many people have complained of nausea and headache, which may also have affected the membership. Grant provides for a follow-up study to explore these and other questions.
the results come on the heels of a successful conclusion of the widely celebrated supposedly CAPRISA 004 trial in south African women, who this was reported that a vaginal gel laced with tenofovir reduces 39% of infection. "this means that more CAPRISA we have crossed the Rubicon," said Mayer, who led one of the two iPrEx sites in the United States . "Antiviral Chemotherapy works, no doubt."
A major difference between the iPrEx and CAPRISA trials is that the gel is an experimental product and are not on the market. Truvada, however, is a popular anti-HIV treatment, and may be prescribed for "off-label" by any doctor. 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 $ 1,000 a month for products manufactured by Gilead.
Gilead says he wants to have frank discussions "" with the US Food and Drug Administration and other stakeholders before it decides to seek licensure for as Truvada preventive. "We have, I think, a very interesting discussion about the potential risks and benefits associated with this type of modality, and I think that will govern what we choose to do so," says Howard Jaffe, president of the Gilead Foundation, a nonprofit launched by the company to help poor communities to combat HIV and hepatitis B and C.
This new success of prevention also raises fundamental questions about how to spend the money to better counteract the AIDS epidemic. "for a country that has not yet reached the level of care in terms of supply antiretovirals to save people's lives, I think it will be some time before we would start using ARVs orally for prevention, "said Salim Abdool Karim, an epidemiologist at the University of KwaZulu-Natal in Durban, South Africa, who co-directed the CAPRISA study.
Another thorny ethical question is whether studies of vaccines and other prevention with men who have sex with men should now use Truvada as a placebo, which clearly offers more benefits than the standard dummy preparation. Fauci said NIAID will now examine this issue in all prevention studies they have planned or underway.
Schooley of UCSD, echoing many of his colleagues, warns that only preventive person by himself can prevent HIV, which infects people in different ways in a variety of conditions. "People looking for one intervention to the impact of the epidemic are the same as those who want a single battle to end the war in Afghanistan," says Schooley. "But it is quite clear the most powerful tools we have right now are drugs."
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