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Microbicide gel fails to work in large international trial
Gus Cairns, 2011-11-25 23:30:00
HIV prevention researchers and campaigners reacted with disappointment today when a trial of a tenofovir-containing microbicide gel was stopped because it had not prevented any more HIV infections than a placebo gel.
The VOICE (Vaginal and Oral Interventions to Control the Epidemic) trial is a large HIV prevention trial involving 5,029 women in South Africa, Zimbabwe and Uganda, run by the Microbicide Trials Network (MTN), a US-based research consortium funded by the US National Institute of Allergies and Infectious Diseases.
VOICE has been investigating two different HIV prevention methods, oral pre-exposure prophylaxis (PrEP) and a vaginal microbicide gel, with both pills and gel used daily regardless of sexual activity. Oral PrEP was given in two different drug formulations: tenofovir (Viread) tablets or tenofovir + emtricitabine (FTC) tablets (Truvada). In all, there were five arms of just over 1,000 women each: a daily tenofovir, Truvada or placebo pill, or daily vaginal application of tenofovir or placebo gel.
The tenofovir-tablet arm was called off in September when it failed to demonstrate efficacy. More recently, on 17 November, a pre-scheduled meeting of the study’s Data and Safety Monitoring Board (DSMB) established that HIV incidence was almost identical in women using tenofovir gel and ones using placebo gel. There were six infections per 100 women a year in women using tenofovir and 6.1 a year in women using placebo. (A trial's DSMB is a group of independent experts who are the only people to see the unblinded data and know which subjects are taking placebo and which drug).
As a result both the tenofovir-gel and placebo-gel arms have now been stopped, leaving only the Truvada and placebo-pill arms continuing. Unless these too are stopped early, final data collection will occur mid-2012 and the VOICE trial’s full results should be ready by the beginning of 2013.
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