Nature Medicine | Spoonful of Medicine

Trials bolster case for preemptive use of HIV drugs to reduce transmission rates

Results from two trials released today provide the first evidence that taking antiretroviral drugs can prevent HIV infection among heterosexual men and women.

The preventative strategy, known as pre-exposure prophylaxis (PrEP), was first shown to be effective among gay men. But PrEP suffered a setback in April when a study testing the drug Truvada among women in Africa had to be halted prematurely owing to lack of efficacy. The new trial data, however, shows that the approach has broad potential in the quest to prevent HIV transmission, according to experts in the field.

“This is the first strong, compelling evidence that PrEP can work in this population,” said Kevin Fenton, director of the National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention at the US Centers for Disease Control and Prevention (CDC), during a press briefing earlier today. “It’s a major milestone.”


Both of the newly announced placebo-controlled trials support the use of PrEP in both heterosexual men in women. The CDC’s TDF2 study included 1,200 Botswanan adults under the age of 30 — half of whom received Truvada, a combination of the two retroviral drugs tenofovir and emtricitabine. After just over a year on average, the investigators observed a 63% reduction in HIV transmission among people taking the pill.

The second study, Partners PrEP, funded by the Bill and Melinda Gates Foundation and based in East Africa, observed transmission rates over an average of 18 months in couples in which one partner had HIV and the other did not. This trial reported a 73% lower incidence of HIV transmission when the uninfected partner took Truvada and 62% lower with people taking tenofovir alone. By comparison, last year’s study in gay men reported 42% effectiveness over an average of 19 months.

“These studies are showing very clear evidence of protection associated with use of PrEP in both men and women,” the University of California–San Francisco’s Robert Grant, who led the successful PrEP study in gay men, told Nature Medicine.

These results come hot on the heels of yesterday’s news that California-based Gilead Sciences, which donated Truvada for the trials, will license the patents to these drugs to the Medicines Patent Pool (MPP). The MPP will then make the intellectual property available to generic manufacturers in developing countries to provide greater access to inexpensive HIV medication. Today’s announcement should make its production and distribution even more needed. Gilead Sciences was unavailable for comment.

For more on PrEP, see:

• Our Q&A with Robert Grant from April of this year.

• ‘Trial success spurs planning for rollout of HIV prevention pills’, from the April 2011 issue of Nature Medicine.

• ‘A preemptive strike against HIV’, a 2009 news feature.

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