ScienceNOW published an encouraging update this afternoon on the results of two pre-exposure prophylaxis (PrEP) trials in sub-Saharan Africa. To quote the opening paragraph of the report:
It's a bad day for the AIDS virus. Results from two studies in sub-Saharan Africa, simultaneously announced today, show for the first time that daily doses of anti-HIV pills taken by uninfected men and women can prevent heterosexual transmission of the virus. Widely hailed as a "breakthrough" in HIV prevention by public health officials, the studies—one of which dropped its placebo arm today because of the convincing effects of the intervention—add powerful new tools to derail transmission of the virus in the population that accounts for most of the 34 million infections in the world.
For those of you not familiar with the way clinical research is done, most studies are "double-blind"--meaning that neither the researchers nor the test subjects know whether the subjects are receiving the trial compound or a placebo. This is done to prevent attempts to "steer" the results in one direction or the other. However, on most trials that involve catastrophic or deadly illnesses, an independent oversight board will sneak peeks behind the veil of ignorance (to steal a term from John Rawls) to monitor progress of the study. If that review board finds that the proposed treatment or intervention has either no effect at all in comparison to the placebo, a deleterious or a harmful effect, or a significant beneficial effect, it will either halt the study outright (in the first two cases) or, as happened here, recommend dropping the placebo arm and giving everyone in the study the proposed treatment.
The news isn't perfectly rosy, however. The good news is that antiretroviral drugs given before actual exposure significantly reduce the risk of subsequent infection (all other things being equal). The bad news is, antiretrovirals are expensive, and may have side effects (particularly after long-term use). As the Science staff noted:
Aside from altering the design of clinical trials, the new data raise difficult financial questions. Truvada now is licensed only as an HIV treatment. If regulators change the drug's label to indicate that it works as a preventive, this could prove critical to whether insurers and governments will pay for Truvada PrEP, which at a discounted rate still costs more than $100 a year when used daily. But the world cannot now afford to treat all the already-infected people who need antiretrovirals, raising the dilemma of where scarce funds should go, to prevention or treatment. Further complicating matters, treatment makes infected people less infectious and is a form of prevention itself; next week, the World Health Organization is expected to recommend that all infected people in discordant couples receive ARVs—a huge challenge for many resource-limited countries.
On balance, though, I think this is a development worth celebrating.