Closure of oral Tenofovir arm in VOICE Pre-Exposure Prophylaxis trial: PrEP as a “niche intervention”?

via Incidence, by Roger J. Tatoud

The Microbicides Trial Network (MTN) September 28th that its VOICE (Vaginal and Oral Interventions to Control the Epidemic, MTN003) HIV Pre-Exposure Prophylaxis (PrEP) prevention study will discontinue the daily oral tenofovir arm of the trial. The decision follows an interim review of the trial’s data by its Data Safety and Monitoring Board (DSMB) which recommended that VOICE stops evaluating the oral tenofovir tablet (TDF, brand name Viread), because it will not be possible for the study to show a difference in effect between the drug and the placebo tablet (futility) for the prevention of HIV infection in the context of that study. Importantly, the DSMB did not found any safety issues associated with the use of TDF in any arm of the trial.

This is the third PrEP trial, after FEM-PrEP and TDF2, for which an interim review of the trial’s data led to a change of course of the study. Because the four other arms of the VOICE trial continue, there are no data available publicly yet to explain why tenofovir would not show effectiveness in this study when three other studies showed a dramatic reduction in the risk of HIV infection with tenofovir alone or in combination with another antiretroviral (see table below). However, Sharon Hillier and Ian McGowan of the Microbicide Trials Network noted that the study’s population – predominately women in their 20’s, could be an important factor.

“If there’s one thing we’ve learned over the years it’s that unmarried women in their 20s are in a very different place in their lives than married women in their 30s. People in different circumstances will make different choices about their use of condoms, their choice of partners and whether or not to use a biomedical prevention product. As we continue the VOICE trial we recognize that there could be many factors that influenced the outcome with oral tenofovir, and even when we have more information available to us, understanding what exactly happened (or not) will not be simple.”

If confirmed (a full analysis of the data will not be available before several months) this would add to the challenge of defining a strategic use for PrEP in the general population or in populations at risk.

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[If an item is not written by an IRMA member, it should not be construed that IRMA has taken a position on the article's content, whether in support or in opposition.]

Microbicide Trials Network Statement on Decision to Discontinue Use of Oral Tenofovir Tablets in VOICE, a Major HIV Prevention Study in Women

via Microbicide Trials Network

VOICE, an HIV prevention trial evaluating two antiretroviral (ARV)-based approaches for preventing the sexual transmission of HIV in women – daily use of one of two different ARV tablets or of a vaginal gel – will be dropping one of the oral tablets from the study. The decision to discontinue use of tenofovir tablets in VOICE comes after a routine review of study data concluded that the trial will not be able to demonstrate that tenofovir tablets are effective in preventing HIV in the women enrolled in the trial. VOICE will continue to test the safety and effectiveness of the other oral tablet, Truvada®, a combination of tenofovir and emtricitabine, and of the vaginal gel formulation of tenofovir.

Importantly, the review, which was conducted by the National Institute of Allergy and Infectious Diseases (NIAID)’s independent Prevention Trials Data and Safety Monitoring Board (DSMB), identified no safety concerns with any of the products being studied in VOICE.

VOICE – Vaginal and Oral Interventions to Control the Epidemic – involves 5,029 women at 15 trial sites in Uganda, South Africa and Zimbabwe. The trial is being conducted by the Microbicide Trials Network (MTN), an HIV/AIDS clinical trials network funded by the National Institute for Allergy and Infectious Diseases with co-funding from the Eunice Kennedy Shriver Institute for Child Health and Human Development and the National Institute of Mental Health, all components of the U.S. National Institutes of Health.

The study was designed with five study groups: tenofovir gel, an inactive placebo gel, oral tenofovir, oral Truvada and an inactive placebo tablet. The women in each group (about 1,000) are asked to take their assigned study product daily. VOICE is the only trial evaluating the daily use of an ARV tablet – an approach called oral pre-exposure prophylaxis, or PrEP – and a vaginal gel in the same study. This design is important for determining how each product works compared to its control (placebo gel or placebo tablet) and which approach women prefer.

On September 16, 2011, the NIAID Prevention Trials DSMB reviewed VOICE study data for the period between Sept. 9, 2009, when the study began, and July 1, 2011. Based on this interim review, the DSMB determined that it was not possible to show whether oral tenofovir tablets were any better than a placebo for preventing HIV in the women assigned to that study group. The DSMB therefore recommended that the women randomized to the oral tenofovir tablet group discontinue their use of the study product. This recommendation does not apply to the women in the groups using either the tenofovir gel or oral Truvada tablets, or the corresponding placebos; the DSMB recommended that these four study groups continue in VOICE.
 
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[If an item is not written by an IRMA member, it should not be construed that IRMA has taken a position on the article's content, whether in support or in opposition.]