A pill that's currently used to treat HIV infection can also
greatly reduce the risk of acquiring HIV among at-risk men, according to the
findings from a large clinical trial.
Each year more than 2.5 million people worldwide are
diagnosed with HIV, the virus that causes AIDS. Although progress has been made
in reducing the number of new infections, scientists continue to search for
more effective strategies to block HIV's spread. Current prevention strategies
rely on behavioral changes, such as condom use, abstinence or fewer sexual
partners.
Clinical trial
Some studies in animals and humans have hinted that the
antiretroviral medications now used to treat HIV might also help to prevent new
infections. To test this idea, a clinical trial was launched at 11 sites in
South America, South Africa, Thailand and the United States.
The study enrolled nearly 2,500 men who have sex with men.
All participants were at least 18 years old and HIV-negative at the time of
enrollment. The trail was sponsored by the National Institute of Allergy and
Infectious Diseases(NIAID), with additional funding from the
Bill and Melinda Gates Foundation.
The men were randomly assigned to receive either a daily
tablet containing 2 common antiretroviral medications (emtricitabine and
tenofovir) or a placebo pill. They were then evaluated each month for HIV
infection. All received condoms, counseling about safe sex practices, and
treatment for other sexually transmitted diseases. The average length of
enrollment in the study was 1.2 years.
Significant results
The results, reported in the November 23, 2010, online
edition of the New England Journal of Medicine, showed that the drug reduced
the risk of acquiring HIV infection by nearly 44 percent. Specifically, 36 HIV
infections occurred among the 1,251 participants who received the
antiretroviral therapy, compared with 64 HIV infections among the 1,248 people
who received the placebo.
The treatment was most effective for those who stuck to the
daily regimen. Participants who took the drug at least half of the time had
about 50 percent fewer HIV infections. Those who took the drug on 90 percent or
more days had nearly 73 percent fewer infections.
The researchers note that their findings are potentially
relevant only to men who have sex with men. Additional studies will examine how
effective the strategy might be in other populations, such as women and
heterosexual men.
"No single HIV prevention strategy is going to be effective for everyone," says NIAID Director Anthony S. Fauci. "Additional research is needed, but certainly this is an important finding that provides the basis for further investigating, developing and employing this prevention strategy, which has the potential to make a significant impact in the fight against HIV/AIDS."
