DSMB stops oral tenofovir monotherapy arm of VOICE PrEP study due to lack of difference compared to placebo

Research into the use of tenofovir as daily prophylaxisis to prevent HIV infection (PrEP) was further complicated by news that one of the key ongoing studies has discontinued women using tenofovir as monotherapy.

On 28 September 2001, the Microbicides Trial Network (MTN), announced that following an interim review by the Data and Safety Monitoring Board (DSMB), the study would be unable to show a reduction in transmissions in patients using daily oral teneofovir and that this arm of the study would be stopped.

Previous studies have reported a strongly protective effect in both high-risk MSM (iPrEX study) and heterosexual populations (Partners in Prevention and TDF2 studys) with a negative result reported in heterosexual women (FEM-PrEP study). The Caprisa 004 study found a 43% protective effect of daily tenofovir gel.

The phase 2b VOICE (Vaginal and Oral Interventions to Control the Epidemic) study has 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.

The remaining four arms will continue to be studied, with results expected in 2013.

Information on the numbers of HIV infections that have occurred in any of the study arms will not be available until this time. Without this analysis it is impossible to know explain the current study results.

MTN press release. MTN statement on decision to discontinue use of oral tenofovir tablets in VOICE, a major HIV prevention study in women. (28 September 2011):
http://www.mtnstopshiv.org/node/3619