Trial Shows First-Ever Reduction in HIV Infections with Microbicide Candidate; Other Studies Indicate Effectiveness of PrEP against SHIV Infection in Animals
A new study released at the 16th Conference on Retroviruses and Opportunistic Infections (CROI) in Montreal, Canada, shows that a microbicide candidate or gel known as PRO2000, designed to lower the risk of HIV infection when applied before intercourse, appears to have a 30 percent level of effectiveness in preventing HIV infection. These findings are promising, although not statistically significant, and additional evidence is needed to conclusively determine whether PRO2000 is an effective microbicide.
Data from the multi-site clinical trial, known as HPTN 035 and conducted by the Microbicide Trials Network, showed that women who received the PRO2000 candidate, plus condoms, had 30 percent fewer HIV infections than those who received condoms or condoms plus a placebo gel. According to Dr. Salim Abdool Karim of the Center for the AIDS Program of Research in South Africa, “It’s very exciting that PRO 2000 might have a positive effect. Now we need a trial that’s big enough to show whether this is a statistically significant effect.” Researchers conducting a separate efficacy trial of PRO2000 in South Africa, Tanzania, Uganda and Zambia, which is in its final stages, will soon obtain more definitive data regarding the candidate’s effectiveness. Data on another microbicide candidate tested in the HPTN 035 trial, BufferGel, did not show a reduction in HIV infection risk among women.
In other HIV prevention news, researchers at the U.S. Centers for Disease Control and Prevention (CDC) presented study findings at CROI showing that two different strategies of pre-exposure prophylaxis, or PrEP, were effective in monkey studies. One study showed for the first time that the oral administration of Truvada, a combination of two antiretroviral drugs (ARVs), before and after exposure to SHIV, a hybrid of HIV and its monkey equivalent SIV, effectively prevented rectal infection in most rhesus macaques. A second study found that a single-drug gel was just as effective as a two-drug gel in preventing SHIV infection in female macaques. SHIV infection is generally considered an easier target than SIV infection, at least for vaccines.
IAVI strongly supports the continued research and development of both microbicides and PrEP as potential prevention tools to combat HIV and AIDS. An effective microbicide could increase the ability of women to protect themselves from HIV. Evidence to date provides a strong rationale for exploring PrEP as a new tool for reducing the risk of HIV infection. With 7,500 new HIV infections a day, the development of new HIV prevention strategies, including an AIDS vaccine, remains urgent.