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Myron Cohen, MD
July 20, 2010 -- Earlier today in Vienna, Austria, researchers from the Centre for the AIDS Programme of Research in South Africa (CAPRISA) presented the results of a clinical trial testing the safety and effectiveness of an antiretroviral microbicide gel at the International AIDS Society conference.
The microbicide gel, containing a widely used antiretroviral drug called tenofovir, was found to be 39% effective in reducing a woman's risk of contracting HIV and 51% effective in preventing genital herpes infections in the women participating in the trial.
These are the most promising results of a microbicide trial reported to date, and the study is being hailed as a ground-breaking discovery in the fight against HIV/AIDS.
After the results were presented, The Global Campaign for Microbicides hosted a satellite session focused on the study results: "Using Antiretrovirals to Prevent HIV: Implications of the outcome of the CAPRISA 004 tenofovir-gel microbicide trial."
Myron Cohen, MD, director of the UNC Institute for Global Health & Infectious Diseases, was asked to address the session. His remarks are reproduced below:
These are exciting times for HIV prevention research.
With proper use of ART mother-to-child transmission of HIV can be reduced to less than 1/100 births. Circumcision offers men at least 60% reduced risk of HIV acquisition. And now, today, after so many years of research, investigators from Durban, South Africa have demonstrated substantial protection from HIV from an antiviral gel preparation.
I have been asked to discuss my reaction to the news and offer some context.
First of all, I am happy for women, whom I hope in the not-too-distant future can benefit from a product that they control which will protect them from HIV.
Second, I am happy for the investigators who developed this strategy. Tonight we are focused on clinical results. But this clinical trial did not come out of nowhere.
The development of the drug tenofovir, the experiments in the laboratory and in monkeys led to the conclusion that this idea could work. Pharmacologic studies helped to understand the proper dosage. The many scientists-and patients who participated at every stage in the process deserve full credit for the discovery.
Third, I am happy for science. The spread of HIV demands urgency, no doubt. But in the rush to do something—anything—to stop the spread of HIV, we have been forced to take shortcuts that have all too often led to disappointment. The protection benefit observed for tenofovir gel was fully expected from all the preliminary results. Indeed, how could an antiviral gel with high concentration and the proper metabolism fail to offer protection?
Clinical trials built on a strong infrastructure are the icing on the cake, not a visit to a gambling casino. Clinical trials are absolutely essential to preclude unexpected toxicity, to make sure that study subjects will use the product and use it properly, to exclude drug interactions and to gain approval for licensure. The completion of the CAPRISA 004 trial is a giant step forward.
What about the context? What do these results mean, at least in my opinion?
First, I’ll trot out a cliché: this is the end of the beginning, not the beginning of the end. The VOICE trial, which compares daily oral pre-exposure prophylaxis with tenofovir gel, will be used to confirm these results. But we should not be misled: pills for prevention PreP are important and will likely be used in very different settings than tenofovir gel.
Second, the CAPRISA results will galvanize the use and development of other antiviral agents and delivery methods. Cervical rings have terrific potential for long term delivery of antivirals and contraception, and these are already in development.
The suggestion that an antiviral gel might also prevent HSV acquisition is compelling and will likely generate as much excitement as the effects of tenofovir on HIV. Indeed, combination topical products seem inevitable.
Third, we must remember in our excitement that we are not without challenges. Can we get this product made and distributed at reasonable cost? The chance for HIV resistance to tenofovir is greater than zero. The tenofovir gel will need long-term safety studies. Like any other intervention, reliable behaviors are required (i.e. people need to use the product properly and consistently).
These results affect the entire prevention field. If the benefits of tenofovir gel are realized, will the gel be offered as standard of care for women in all prevention trials? If this is the case, the difficulty in proving an intervention works—or works better than tenofovir gel—in a randomized clinical trial will increase dramatically.
But tonight, let’s just celebrate the CAPRISA success. I can tell you from personal experience that success is better than failure. We have been offered a wonderful preview of a new tool in the war on AIDS.
Video of the conference session on the CAPRISA 004 results are available from the Kaiser Family Foundation.
Angela Kashuba, PharmD, associate professor of pharmacy in the UNC Eshelman School of Pharmacy, presented drug concentration results of CAPRISA 004. Her presentation is available for download here.
UNC Infectious Diseases contact: Lisa Chensvold, (919) 843-5719, email@example.com