A study has found that it is possible to contract HIV and become resistant to Truvada while taking the drug as a pre-exposure prophylaxis (PrEP). People have been found to become HIV-positive on PrEP in the past, but this was because they had begun treatment unaware their HIV tests had produced false negative results.
Analysing plasma samples from the 121 people who contracted HIV while participating in the PARTNER PrEP study, researchers tested for resistance against emtricitabine or tenofovir (the drugs found in Truvada). Five participants were found to have drug resistance — three of these were discovered to have been acutely infected when they started the trial.
This left two, then, who became HIV-positive during the trial and who went on to develop drug resistance to Truvada (most likely to the emtricitabine component). Such an occurrence, say researchers, is rare and the findings should be weighed against the prevention of an estimated 123 new HIV infections over the entire course of the PARTNER study.