Pre-Exposure Prophylaxis or PrEP

Pre-exposure prophylaxis (PrEP) involves putting HIV negative people on antiretroviral drugs (ARV) with the aim of protecting them from HIV infection. This blog looks at some of the pros and cons of PrEP.

Monday, April 18, 2011

Unbelieveably High Adherence Doesn't Guarantee Effectivenss of Truvada

A less well publicized trial of Truvada for pre-exposure prophylaxis has finished early. Not only is it less well publicized, but the results are not being released in full until further notice.

Family Health International's (FHI) press release said "the Independent Data Monitoring Committee (IDMC) advised that the FEM-PrEP study will be highly unlikely to be able to demonstrate the effectiveness of Truvada in preventing HIV infection in the study population."

This trial was like the iPrEx study except that it was testing the use of Truvada to prevent HIV infection in women. The release of preliminary data only contrasts strongly with the way iPrEx data was released, even though the latter data was not particularly impressive.

Adherence appears to have been extremely high, higher than in the iPrEx study. But the rate of new infections was very high, at 5% per year, and there was not difference in rate between those on Truvada and those on a placebo.

Interestingly, 66% of women were using injectible contraceptives. This a popular contraception method in many African countries. Unsafe injection rates, which are extremely high in developing countries, might explain at least some of the transmissions.

Higher pregnancy rates were found among women who were taking Truvada and this was quite unexpected. It's good to hear that researchers and other commentators are being cautious, unlike with the iPrEx trial results.


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