International PrEP study (VOICE) discontinues use of tenofovir vaginal gel due to lack of efficacy
1 December 2011. Related: Transmission and prevention.
Simon Collins, HIV i-Base
On 17 November a large international Phase 2b study looking at interventions to reduce HIV sexual transmission announced that it will discontinue use of a 1% tenofovir vaginal gel and matched placebo gel due to the study’s data and safety monitoring board (DSMB) finding no difference in efficacy between these two groups. 
In the latest review the DSMB found a 6% HIV incidence rate among participants in both the tenofovir gel group and the placebo gel group. No other safety concerns (other than efficacy) have been reported with any of the studied interventions.
This is the second major change in the US NIH funded VOICE study (Vaginal and Oral Interventions to Control the Epidemic) in two months. In September, we reported in HTB that the use of daily oral tenofovir was discontinued for a similar lack of efficacy. 
The study originally enrolled more than 5,000 HIV-negative women at 15 clinical research sites in Uganda, South Africa and Zimbabwe. The study randomised women to one of five groups: daily oral tenofovir, daily oral Truvada, daily oral placebo tablet, daily tenofovir gel or daily placebo gel.
Only the daily oral Truvada and oral placebo arms will continue to be studied, with results expected in 2013.
- NHI press statement: NIH discontinues tenofovir vaginal gel in ?VOICE’ HIV prevention study: product safe but no more effective than placebo. (25 November 2011).
- DSMB stops oral tenofovir monotherapy arm of VOICE PrEP study due to lack of difference compared to placebo. HIV Treatment Bulletin (HTB), October 2011.
Statement and Q&A from Microbicide Trials Network (MTN):