At the annual Conference on Retroviruses and Opportunistic Infections (CROI) in Boston on Monday, researchers "suggested the potential" of a gel containing the antiretroviral drug tenofovir to reduce the risk of anal HIV transmission, TIME's "Healthland" blog reports. With previous trials showing the gel reduced HIV vaginal infection risk, "[r]esearchers have wanted to know whether the gel could protect against anal transmission of the virus, since the risk of infection from unprotected anal sex may be more than 20 times that of unprotected vaginal sex," according to the blog (Melnick, 2/28).
"In the new study, the first of three phases needed before the treatment can get approval from the U.S. Food and Drug Administration, researchers [from the Microbicide Trials Network] tested tenofovir gel, the oral tenofovir pill and a placebo gel in 18 HIV-negative people who abstained from sex," HealthDay News/U.S. News & World Report adds (2/28).
"The trial directly compared the anti-HIV activity of a single dose of oral tenofovir to a single dose of rectally-applied tenofovir gel … followed by six days of at-home dosing of tenofovir gel or a placebo gel, with the last and seventh dose given in the clinic," according to an MTN press release (2/28). The researchers then biopsied cells to see how well they "defended themselves against HIV," HealthDay News/U.S. News & World Report continues (2/28).
"The researchers found that HIV was significantly inhibited in tissue samples from participants who used tenofovir gel daily for one week compared to tissue from participants who used the placebo gel," according to the MTN press release. "The single dose of oral tenofovir did not provide any protection against HIV in rectal tissue samples," the release states (2/28). "The continuing research - and possible eventual manufacture of a commercial anti-HIV rectum gel - could have monumental effects for both at-risk men who have sex with men (MSM) and women who engage in anal sex," IRIN/PlusNews writes (3/1).
"We are very encouraged about these findings that indicate applying tenofovir gel topically to the rectum could be a promising approach to HIV prevention," lead author Peter Anton, director of the Center for Prevention Research at UCLA, said, Agence France-Presse reports. However, he noted more trials were needed to better address issues related to side effects of using the gel that were reported by several participants (2/28).
"These are early results, but help set the stage for current and future trials of rectal microbicides and the development of a rectal-specific formulation of tenofovir gel," the University of Pittsburgh's Ian McGowan, co-principal investigator of MTN, who helped lead the study said, according to the MTN press release (2/28).
Also Monday, researchers presented data from a Phase II trial "that compared the oral [tenofovir] tablet to the gel in 144 women in the United States, Uganda and South Africa," AFP adds. They "found that the gel resulted in a 100 times higher concentration of the drug in vaginal tissue. … The tablet was associated with a 20-times higher active drug concentration in blood," according to the news service (2/28).
"[A]lthough we saw much higher drug concentrations in vaginal tissue with the gel, how the differences between the gel and the tablet will translate in terms of protective effect, we can't say just yet," Craig Hendrix of Johns Hopkins University, who led the trial, said, according to a second MTN press release. "We don't know for certain where the drug needs to be or how much of the drug is needed to be most effective against HIV," he added. The release elaborates on other details of the trial, including self-reports of preference between the two prevention strategies (2/28).
Media Examine Why Doctors Have Been Slow To Prescribe Truvada For Prevention
Three months after researchers released a study of MSMs and transgender women that revealed a daily dose of Gilead's Truvada - a combination of the AIDS drugs emtricitabine and tenofovir - reduces the risk of contracting HIV, "doctors say they're wary about giving healthy people a $12,000-a-year medicine that has side effects including nausea and kidney damage, and may not be used as regularly as needed. They also say they're not often asked to make the drug available for that use," Bloomberg reports. The topic is expected to receive attention this week at CROI, according to the news service, where "[a] dozen presentations are scheduled that will examine Truvada's long-term use in uninfected people, its side effects and safety, the best candidates for it and the potential risk of developing drug-resistance with inconsistent use."
The article compares new Truvada prescriptions written for patients between Dec. 1, 2010, and Feb. 19, 2011, to the year prior, and describes several reasons why patients are not actively seeking Truvada, including the cost of the drug and stigma attached to taking antiretrovirals (Cortez/Bennett, 2/28).
"Gilead hasn't even applied to the Food and Drug Administration to expand Truvada's label [from its current use as a drug for people living with HIV] to include prevention of the virus in male-to-male sex. That filing could happen in March or April," the San Francisco Business Times' "Bay Area Biz Talk" reports (Leuty, 2/28).
Bloomberg also describes ongoing efforts to better understand the groups who would benefit the most from Truvada as a preventive strategy, also known as pre-exposure prophylaxis, or PrEP. The article reports on discussions about how to best roll out the use of Truvada in the U.S. and globally.