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Cancellation of VOICE trial arm a blow to HIV prevention

VOICElogo-300b.jpgIn a second setback in as many months, researchers running a major HIV prevention trial have cancelled one of its arms after learning that a vaginal gel was not effective in protecting women who use it from acquiring the virus.

In press releases issued on 25 November, the US National Institute of Allergy and Infectious Diseases in Bethesda, Maryland, which is funding the study in sub-Saharan Africa, and MicrobicideTrials Network (MTN) of Pittsburgh, Pennsylvania, which is running it, said that women using a vaginal gel containing the anti-retroviral drug tenofovir were just as likely to contract the AIDS-causing virus as those applying a placebo gel. Among both groups, about 6% of women were infected during the course of a year. The lack of effect was discovered in a 17 November review of study data by an independent data safety and monitoring board.

The HIV prevention trial, dubbed VOICE, for Vaginal and Oral Interventions to Control the Epidemic, is being conducted in more than 5,000 uninfected, sexually active women in Zimbabwe, Uganda and South Africa. The MTN researchers said in a press release that the cancellation, “although disappointing…adds a critical dimension to discussions about the future of tenofovir gel.”

In September, another arm of the trial, comprising women taking oral tenofovir tablets, was cancelled because an independent data-oversight board determined that the trial would not be able to prove the oral tablets effective. The latest cancellation also comes just two days after the Global Fund to Fight AIDS, Tuberculosis and Malaria announced that it is halting funding of new grants until 2014, owing to budget troubles.

In sub-Saharan Africa, where women account for 60% of adults with HIV, the main driver of acquisition is unprotected heterosexual intercourse. Because many women in these countries are not in a position to insist on condom use by their partners, developing an effective microbicide that can be applied by women without their partner’s knowledge or involvement has been considered key to slowing the epidemic.

After years of disappointments for the microbicide field, great hope had been placed in tenofovir in 2010 after the publication of a promising study in Science.

It enrolled 889 uninfected, sexually active women in Durban, South Africa. The annual rate of virus acquisition for those using tenofovir vaginal gel before and after sex was 5.6%; for those using a placebo gel it was 9.1%. The results prompted cheers in the audience to which they were announced. The present trial, it was hoped, would replicate those findings.

Following this cancellation, two arms of the VOICE study remain active: women taking Truvada, a combination of tenofovir and the anti-retroviral drug emtrictabine; and women taking an oral placebo tablet. Both tenofovir tablets and Truvada are made by Gilead Sciences of Foster City, California.

None of the study data will be unblinded until the remaining arms are complete, leaving researchers unable at the moment to investigate what might have caused the failures. The trial is expected to be complete in June 2012, with final study results anticipated in early 2013. A public analysis of the cancelled arms may come sooner.


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