One Small Step for Microbicides
The results are in, and it’s good news for microbicides development, as well as for prevention advocates around the globe. At this year’s Conference on Retroviruses and Opportunistic Infections (CROI), researchers presented promising data on a candidate microbicide known as PRO 2000, showing that women who used the gel had a 30% reduction in HIV transmission.
Microbicides are experimental substances designed to prevent or reduce the likelihood of HIV transmission and often other sexually transmitted infections. Microbicides are applied vaginally or anally, prior to sex. These substances will hopefully one day provide an alternative option or backup for the millions of women and men around the world who are unable to use condoms. While the recent findings fall short of the long-term goal of developing a microbicide with 60% or higher efficacy in blocking HIV transmission, they do demonstrate important progress toward that goal.
Pro2000 was studied in a clinical trial called HPTN 035, which was conducted at seven sites in Africa and the U.S. enrolled about 3,100 participants and was conducted between February 2005 and September 2008. HPTN 035 was unique for a couple of reasons. It was the first microbicide trial to examine two candidate gels (the second being Buffergel) that worked in two different ways. HPTN 035 was also the first to include two comparison control groups. By also including a “no gel” group the researchers hoped to determine whether the use of a gel in itself reduced transmission or whether the antimicrobial substance was essential for block HIV transmission. The researchers found no substantial differences in the HIV infection rates among people using the placebo gel group, the “no gel” group or Buffergel. In contrast, the use of the Pro2000 gel reduced HIV transmission rates by about one-third.
Coming after a period of disappointing study results and study closures, the successful completion of the HPTN 035 trial is reason for celebration. Not only did the trial build on the experience of earlier trials in engaging communities and recruiting interested participants, they were also able to retain participants who reported consistent use of the study gels. HPTN 035 demonstrated continued safety of the Pro2000 gel and participants overwhelmingly found it to be “user friendly.” In fact, the Microbicide Trials Network reported that in this particular study, nearly all of the women (99%) said that they would use the gels if they were approved.
Currently, the trial sponsors and researchers do not have plans to enter the next stage of research for this microbicide. Another Pro2000 clinical trial with a larger participant sample is ongoing with results expected in late 2009.
So what does this mean for advocates and those in desperate need of these vital prevention tools? Well, not too much for now. We have to keep watching and waiting to see what ongoing and future microbicides trials reveal. Hopefully, these studies will lead to the development of highly effective microbicide gels that can be mass produced at low cost and widely distributed to those who need them most. Unfortunately, it looks like that outcome may still be years away. So, we’re not there yet but we’re one step closer. And a step closer is a step in the right direction.
