A once-a-day pill is effective in preventing HIV infection, according to two big new human studies released last week. This could add a preventive pill to the toolkit of HIV prevention, alongside condom use, abstinence, and vaginal microbicides.
Of course, these human trials would not have been possible had the drugs not been first shown to work in animal studies. Both trials were conducted in Africa. In one, conducted in Kenya and Uganda, 4,758 couples where one partner was infected with HIV and the other uninfected took a daily pill containing a mix of tenofovir and emtricitabine, called Truvada, or a placebo. The Truvada pill reduced the infection rate by 73 percent.
In a second study, 1,200 sexually active young adults in Botswana took daily Truvada and their infection rate was 63 percent lower than placebo.
All participants in both studies also received condoms and counseling on HIV prevention. The successful trials follow two other studies. Truvada showed a success rate as high as 90 percent in a trial involving gay men in six countries released last year. But another trial in African women was stopped early because it did not appear to be working – possibly because the participants were not taking their medicine or giving it to others.
Tenofovir, one of the key drugs in the Truvada pill, was also the key ingredient in a microbicidal gel shown to prevent HIV infection in a major trial last year.
So what’s the connection to animal research? These are all large trials conducted in human beings – the gold standard for figuring out if a treatment is going to work or not. But you can’t start handing out pills and intervening in the lives of thousands of people unless you have a pretty good idea that it’s going to work. In the case of tenofovir and other anti-HIV drugs, part of the route from lab bench to clinical trial was through testing in monkeys infected with simian immunodeficiency virus (SIV), the closest known relative to HIV. Success in those monkey experiments meant that tenofovir could go forward – and help save lives around the world.