FEM-PrEP prevention study using daily Truvada halted during enrolment: interim analysis shows similar infection rates in active and placebo arms

On 18 April a press statement from Family Health International announced that the FEM-PrEP study had been stopped by the trials Independent Data Monitoring Committee (IDMC) due to an interim analysis that showed no difference between rates of new HIV infections in the active tenofovir/FTC (Truvada) group compared to the people using placebo. [1]

In this study Truvada or placebo was being taken daily as a pre-exposure prophylaxis prevention (PrEP) treatment against HIV. When the decision to stop the study was taken, almost 2000 women from Kenya, Tanzania and South Africa were enrolled, just over half the planned number of particiapants.

These results are both extremely disappointing and surprising given that a similar study in gay men at high risk of infection (young, multiple partners and exposures, high alcohol use etc) showed a strongly protective effect. [2]

FEM-PrEP was also being run in a high-risk group: 20% of 3752 women who came forward to participant were already HIV positive when screened.

The approximate rate of new HIV infections among trial participants was 5% per year. The 56 new HIV infections were equally distributed between the active and placebo arm. Although adherence was reported at 95% similar to self-reported adherence in the iPrEX study, a pharmacokinetic sub-study in iPrEX indicated that actual adherence was far lower.

Further analyses from the study are needed to explain the starkly different results compared to iPrEX. The level of protection was expected to be similar based on systemic exposure to the same prophylactic drugs, but this would also be dependent on drug levels achieved in the genital tract.

As with all prevention studies, all participants were given support to reduce their risk of HIV, including advice to always use condoms.