More Favorable Results on PrEP, But ...

As part of the usual flurry of studies released just before major scientific meetings, results of two pre-exposure prophylaxis (PrEP) trials in heterosexual men and women have just been made public:

• In the CDC TDF2 study, 1200 HIV-uninfected men and women in Botswana were randomized to take oral tenofovir/FTC or placebo daily. Tenofovir/FTC was found to reduce the risk for HIV acquisition by 63%. The risk reduction was even greater (78%) among individuals believed to be taking the study drugs.
• In the Partners PrEP Study, the uninfected partners in nearly 5000 HIV-serodiscordant couples in Kenya and Uganda were randomized to take oral tenofovir/FTC, oral tenofovir alone, or oral placebo daily. Relative to placebo, tenofovir/FTC was associated with a 73% reduction in risk for HIV acquisition, and tenofovir alone was associated with a 62% reduction in risk. The protective effects were similar for both men and women.

So, the score so far on PrEP studies: four positive (if you include CAPRISA 004, which used tenofovir vaginal gel, and of course iPrEX) and one negative (FEM-PREP, in women). Other key (if unsurprising) findings are that PrEP works better if you take it and that it's pretty safe.

One possible interpretation of these results is that we should do everything we can to get HIV-negative individuals from serodiscordant couples on PrEP as soon as possible.

But here's another thought: Why not get all the infected people -- especially in established serodiscordant couples, as in Partners PrEP -- on ART? According to Study 052 (with many more details to come next week at IAS), the net result of this strategy would be both a personal and a public health benefit. Sure, HIV treatment with three drugs is more expensive than one or two for PrEP, but it strikes me that the double benefit (i.e., to the individual and the uninfected partner) easily justifies the incremental cost.

If the final results of 052 are as impressive as the glimpse we've received thus far, one could see oral PrEP becoming a strategy limited to high-risk individuals who do not have steady partners (e.g., MSM similar to those in iPrEx, or certain individual from hyperendemic areas).

Which means that the best way to prevent HIV with meds is usually to treat those who have it -- and only rarely to treat those who don't.

Paul Sax is Clinical Director of Infectious Diseases at Brigham and Women's Hospital. His blog HIV and ID Observations is part of Journal Watch, where he is Editor-in-Chief of Journal Watch AIDS Clinical Care.