Pre-exposure prophylaxis study for Cambodia

Australian researchers have teamed up with the US and Cambodia to conduct a study of the potential of the HIV antiviral tenofovir, taken daily, to prevent HIV infection in women at high risk.

Female sex workers, who in Cambodia currently stand up to a 26 percent chance of becoming HIV-infected within their first year working in the sex industry, will be invited to participate in a ground-breaking study which researchers acknowledge is challenging, but necessary.

The research partners, supported by the Bill and Melinda Gates Foundation and the University of San Francisco, and including Australia’s National Centre in HIV Epidemiology [1]The branch of medical science that deals with the study of incidence and distribution and control of a disease in a population. and Clinical [2]Pertaining to or founded on observation and treatment of participants, as distinguished from theoretical or basic science. Research, will be looking at whether the use of antiretroviral [3]A medication or other substance which is active against retroviruses such as HIV. therapy can prevent HIV-negative people from becoming infected, by fighting the replication of virus [4]A small infective organism which is incapable of reproducing outside a host cell. as it first enter’s the body’s cells.

It is a potentially risky approach: tenofovir, like all HIV antivirals [5]A medication or substance which is active against one or more viruses. May include anti-HIV drugs, but these are more accurately termed antiretrovirals., has a range of potential short and long-term side effects, ranging from allergic reactions and gastrointestinal disturbances to more serious, though rare, long-term effects like kidney damage. The long-term effects of any antiretroviral therapy in HIV-negative populations are not known and have never been tested.

Researchers have accepted the challenge in the hope that this approach — called ‘pre-exposure prophylaxis’ or PREP — may yield a viable prevention strategy for those at risk of HIV infection. Vaccine research is seen to be increasingly flagging in terms of new and viable approaches — especially after the recent failure of Thai trials of AIDSVAX, the only candidate HIV vaccine to have so far reached large Phase III studies. AIDSVAX has now been conclusively shown to have no effect in preventing HIV infection.

No studies have ever looked at whether current antivirals can prevent people from becoming infected with HIV. This study will look at up to 950 women currently at high risk.

Like vaccine studies, devising scientifically robust but ethically acceptable research in this area is extremely complex. Researchers and participants must weigh up the relative risks of HIV infection and drug side effects, as well as the imperative to find new ways to prevent HIV infection, in a world where more than 5 million people are believed to have acquired HIV in 2003 alone.

This issue looks set to become a major new area of debate in HIV/AIDS advocacy, as researchers in the US begin to weigh up PREP’s potential for preventing HIV infection in other high-risk groups, possibly including some gay men.