Using antiretroviral drugs, such as tenofovir, to try to prevent HIV infections is known as pre-exposure prophylaxis, or PrEP. There are currently numerous studies taking place to determine if PrEP is effective in stalling the spread of HIV among people at high risk, including gay and bisexual men.
More information and data needs to be gathered from these PrEP studies, but this Phase II safety study “lends additional assurance that the strategy may be safe among MSM (men who have sex with men), should it prove effective,” according to an ARCA press release.
Researchers hope tenofovir, marketed as Viread, might one day help people from contracting HIV. (Photo courtesy Gilead)
“This idea is like malaria prevention in that, if effective, it would keep the virus from establishing an infection,” said Dr. Melanie Thompson, principal investigator at ARCA and senior author of the study.
While this safety study does not prove tenofovir is effective in the prevention of HIV, the fact it is safe among HIV-negative men gives the overall PrEP studies more hope in finding future ways to prevent the spread of HIV, Thompson said.
“Previous large tenofovir studies have been conducted in persons with HIV, so it was important to be sure that the drug was safe in uninfected people,” she said. “For that reason, our study was much smaller (400 men) and not capable of determining whether the strategy would be effective for HIV prevention.”
But this study is helpful, she stressed, because PrEP is considered one of the most promising new prevention methods currently being explored. If effective, PrEP could be used along with condoms and other risk-reduction methods, to help slow the HIV epidemic in the U.S. and around the world.
“We are extremely pleased with the outcome of the study,” Thompson said in a statement. “We need to explore many different avenues to prevent HIV infection, an epidemic that disproportionately affects African Americans and gay and bisexual men of all races in the United States.
“If other studies show that PrEP is effective, millions of infections could be prevented globally,” Thompson said.
The CDC estimates that 56,000 new HIV infections occur in the U.S. every year, and more than 2.7 million people are infected around the world on an annual basis.
The study’s main goal was to examine whether it was safe for the 400 HIV-negative gay and bisexual men to take daily a 300 milligram tablet of tenofovir disoproxil fumarate.
ARCA enrolled 121 patients from Atlanta and had the most enrollees of color —32 percent were non-white (27 percent African-American, 1 percent Asian- Pacific Islander, 4 percent other races) and 12 percent were Hispanic. The tenofovir study ran from February 2006 to summer 2009.
The median age of participants was 39 and overall the races were 73 percent white, 15 percent African American, 4 percent Asian Pacific Islander and 9 percent Hispanic.
Scientists note that one of the greatest risks of PrEP is those using PrEP might start undertaking riskier sex behaviors, believing they are now immune because of a drug. This phenomenon is known as “behavioral disinhibition” or “risk compensation.”
For this study, however, researchers found no overall increase in unprotected anal sex in men taking a study pill compared to those not taking a study pill during the first nine months of the study.