Oral pre-exposure prophylaxis (PrEP) against HIV

The iPrEx trial tested whether an HIV drug taken by healthy people could keep them from being infected. It enrolled 2,499 HIV-negative men and transgender women who have sex with men at 11 sites in Peru, Ecuador, Brazil, South Africa, Thailand and the United States. Participants were randomly assigned to a daily pill combining emtricitabine and tenofovir disoproxil fumarate or to a placebo, and all received HIV testing, counseling and condoms.

Over 3,324 person-years of follow-up, 100 participants became infected: 36 in the drug group and 64 in the placebo group, a 44 percent reduction. Robert Grant and colleagues reported the result in the New England Journal of Medicine in November 2010. The protection tracked pill-taking. In the drug group, participants with detectable drug in their blood had a 92 percent lower risk of infection than those without.

Other trials pointed the same way when people took the pills. In Partners PrEP, among HIV-discordant heterosexual couples in Kenya and Uganda, the combination cut infections by 75 percent, and in TDF2, among heterosexual men and women in Botswana, by 62 percent. FEM-PrEP, among women in East and Southern Africa, was stopped early without showing benefit, and its participants took very few of their pills.

Gilead Sciences asked FDA for the new indication in December 2011. On 16 July 2012 FDA approved Truvada, used together with safer sex practices, to reduce the risk of sexually acquired HIV-1 infection in adults at high risk, heterosexual people and men who have sex with men alike. CDC then reviewed the trials for clinicians in its Morbidity and Mortality Weekly Report.