Current HIV Prevention Trials

Microbicide trials

More than a dozen clinical trials are underway to determine whether various gels can prevent male-to-female or male-to-male transmission of HIV infection. These trials are part of a global effort to identify a safe, effective microbicide that could be applied topically to protect users against HIV and other sexually transmitted infections (STIs). There are no proven effective microbicides at this time; ongoing clinical trials, including efficacy trials of candidates using different strategies, will yield results in the coming years. As with any new experimental intervention, the first candidates are expected to be partially effective; however even a partially-effective microbicide could potentially be a powerful prevention tool when used alongside existing prevention strategies such as male and female condoms, risk reduction counselling, and diagnosis and treatment of sexually transmitted infections.

Visit the website of the AIDS Vaccine Advocacy Coalition (AVAC) to see a chart on the status of current clinical trials of microbicide candidates (2009 PDF, 85 KB), including information on sites (countries) and sponsors of such trials.

Pre-exposure prophylaxis (PrEP) trials

Pre-exposure prophylaxis (PrEP) refers to an experimental HIV-prevention strategy that would use antiretrovirals to protect HIV-negative people from HIV infection. PrEP has not yet been proven to work; in the strategy that is currently being tested, HIV-negative people would take a single drug, or a combination of drugs, daily in hopes that this would protect them against HIV infection. Along with AIDS vaccines and microbicides, PrEP is one of the experimental HIV-prevention strategies being tested in clinical trials today.

Take a look at an updated chart (PDF, 65 KB) on www.prepwatch.org outlining ongoing, planned, and recently completed PrEP trials.

Vaccine trials

A range of potential products have entered the HIV vaccine "pipeline," but few have made it to efficacy trials.

Since 1983-1984, when HIV was identified as the cause of AIDS, there have been three Phase III efficacy trials: one among North American men who have sex with men and heterosexual women; one in Thailand involving intravenous drug users; and a third trial, also in Thailand, involving a large community where heterosexual contact is the primary risk factor.

The first two trials involved a candidate called AIDSVAX. They were completed in 2003 and did not find any efficacy. The third efficacy trial in Thailand is ongoing. It is evaluating a prime-boost combination of AIDSVAX and a candidate called ALVAC.

HSV-2 trial

Herpes-simplex virus type 2 (HSV-2) is a sexually transmitted infection that has been linked, in observational studies, to increased risk of HIV acquisition and to higher rates of HIV shedding in the genital tract of people who are coinfected with HIV and HSV-2. On the basis of these observations, three large efficacy trials were launched to explore whether suppressive HSV-2 therapy could be used as an HIV risk reduction strategy. Two of these trials looked at whether HSV-2 treatment could reduce the risk of HIV acquisition among HSV-2 positive, HIV-negative people. The results from these trials were recently announced: there was no evidence of benefit in terms of risk of HIV infection among the people who took twice-daily acyclovir as HSV-2 suppressive therapy.

Another recently completed trial in serodiscordant couples examined whether suppressive therapy for HIV-positive people reduces their risk of transmitting to their sexual partner.

Resources

AIDS Vaccine Clearinghouse

AVAC's HIV Prevention Research: A Comprehensive Timeline