Pre-Exposure Prophylaxis or PrEP

Pre-exposure prophylaxis (PrEP) involves putting HIV negative people on antiretroviral drugs (ARV) with the aim of protecting them from HIV infection. This blog looks at some of the pros and cons of PrEP.

Monday, November 28, 2011

Tenofovir Vaginal Gel Trial Stopped Because It's Ineffective

The Microbicide Trials Network (MTN) have announced that Tenofovir gel will no longer be used in the current VOICE trial (Vaginal and Oral Interventions to Control the Epidemic) shortly after the same decision was made about the oral version. Both arms of the trial have been stopped for the same reason; neither are any more effective than a placebo. Trials of Truvada, a combination of tenofovir and emtricitabine, will continue for the moment.

Incidence, the rate of new infections, was extremely high, at 6%. I wonder if the trial has got any closer to figuring out just why HIV transmission is so high among study participants? For instance, were sexual partners tested and were their HIV types matched? Were possible non-sexual HIV exposures investigated, for example, through unsafe healthcare, traditional healthcare, cosmetic practices, or any others?

All the talk about 'fast-tracking' approval of tenofovir by the US Food and Drugs Advisory for possible production by 2014 that we heard so much of just a year ago has been replaced by the kind of silence we've come to expect from results that can't even be dressed up to look a little bit positive. With viable gels and PrEP pills so far in the future, it might be a good idea to put into effect some low technology (though far less lucrative) HIV prevention programs.

The full results of VOICE are unlikely to be available for some time, perhaps another year or two. But if good data is collected on non-sexual transmission, the thousands of participants will not have wasted their time completely. It won't be much consolation for the hundreds of people whose infections were not prevented, nor the hundreds of thousands of new infections that will occur elsewhere in the meantime, but everyone will benefit if a little less attention is paid to their sex lives, which may not be as relevant as orthodox HIV theory suggests.

Mitchell Warren, the Executive Director of the AIDS Vaccine Advocacy Coalition (AVAC, a front group for the HIV pharmaceutical industry), has expressed disappointment. One researcher is reported to have said "the failure of one method in one trial did not mean that the trial, or the idea of microbicides, had failed." Which is quite true. The failure could be for entirely different reasons, incorrect and unwarrented assumptions about the relative contribution of sexual transmission in serious epidemics being just one.


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