New Development in VOICE Study: oral tenofovir arm discontinued

September 28, 2011 —

Today the Microbicide Trials Network (MTN) announced a change to its VOICE study, a clinical trial designed to evaluate the safety and effectiveness of two different antiretroviral (ARV)-based approaches for preventing the sexual transmission of HIV to women — daily use of one of two ARV tablets or a daily ARV-based vaginal microbicide gel. VOICE will discontinue use of the oral ARV tablet tenofovir in the trial, but continue use of the oral ARV tablet Truvada as well as the tenofovir microbicide gel.

The decision follows an independent interim review of the study data, which concluded that VOICE will be unable to show that oral tenofovir tablets are effective at preventing HIV in this study. No safety concerns were indicated. Please see MTN’s website for its statement and a Q&A document about today’s news.

Recent results of other studies in Africa of oral tenofovir and Truvada have shown promise in preventing HIV in certain adult populations, including heterosexual discordant couples (Partners PrEP study) and heterosexual men and women (TDF2 study). However, an earlier study of oral Truvada among women (FEM-PrEP) was stopped this past April for futility and its findings are currently being reviewed. Once the VOICE study concludes, MTN will review all the data to help understand why oral tenofovir was unable to demonstrate effectiveness among VOICE participants. All of this research provides invaluable data as the field works to advance safe and effective HIV prevention tools for women.

While the discontinuation of oral tenofovir in this trial is disappointing, VOICE will continue to test the effectiveness of oral Truvada and once-daily tenofovir gel, with results expected in 2013. Currently, the US Centers for Disease Control and Prevention is conducting a trial of daily oral tenofovir among male and female injection drug users in Thailand, the only other ongoing efficacy study of oral PrEP, with results expected in 2012. Results from VOICE on tenofovir gel could support the milestone 2010 CAPRISA 004 trial showing proof-of-concept for the product. The FACTS 001 trial just getting underway in South Africa could potentially provide further confirmation of tenofovir gel’s efficacy, with results expected in 2013.

IPM praises the VOICE study team for its commitment to developing ARV-based HIV prevention options for women and its hard work in implementing this trial.  We also express our deep gratitude to the women of South Africa, Uganda and Zimbabwe who have volunteered for VOICE to advance these urgently needed technologies. We look forward to future results from this important ongoing study.