Positive results were announced today from the CAPRISA 004 Phase IIb trial of a of an antiretroviral (ARV) gel formulation called tenofovir for the prevention of HIV acquisition in women. There have been 'invisible condom' microbicide trials for many years, but CAPRISA is the first one to show a significant reduction in HIV transmission.
The drug trials were conducted in KwaAulu-Natal, a rural village in South Africa, and the good news from the village comes just in time for the AIDS 2010 - XVIII International AIDS Conference taking place this week in Vienna. Tomorrow CAPRISA, the Centre for the AIDS Programme of Research in South Africa, will officially report the details of its study to the AIDS conference. Today, however, the study appeared in the online edition of Science.
The trials included almost 900 women between the ages of 18 and 40 who were at high risk for contracting aids through the vagina (60 percent of those with HIV in this region are women). Half of the women in the trial were given tenofovir 1 percent and the other half, a placebo. Their instructions were to use an applicator to inject the gel into the vagina within 12 hours before having sex, and another applicator of the gel as soon as possible after sex.
After the 30 month trial, 38 women who had used the tenofovir gel contracted HIV, compared with 60 women on the placebo gel. The overall risk reduction was 39 percent; however, among women who were strict adherers to the regime (i.e., more than 80 percent of the time), the incidence was 54 percent lower among the tenofovir users. The microbicide use also reduced the risk of contracting genital herpes by 51 percent; the open wounds left by genital herpes makes HIV contraction even more likely.
Some scientists reported being perplexed as to why tenofovir was not more effective at reducing risk of AIDS contraction. When asked by The Washington Post, Anthony S. Fauci, former head of the NIH, currently back to his former job as head of the National Institute of Allergy and Infections Diseases (NIAID) at NIH, suggested...
"My most likely explanation is that you have to go up on the dose. You may have maxed out on 1 percent."
Another trial of 5,000 women is underway now, but results from that trial will not come until 2013.
Sources: CAPRISA, AVAC press release, Science The Globe and Mail, The Washington Post