Paul Sax
from Brigham and Women's Hospital and Harvard Medical School
The iPrEx (preexposure prophylaxis) study published in The New England Journal of Medicine. [1] This is the first efficacy study so far of preexposure prophylaxis, and here are the results:
About 2500 high-risk men who have sex with men entered the study and were randomly assigned to receive either coformulated tenofovir FTC [combination emtricitabine (FTC 200 mg) and tenofovir (TDF 300 mg), known by the brand name Truvada®] or a matching placebo. After about a year of median follow-up, the investigators found that there was a 44% reduction in the risk of acquiring HIV. There were 36 infections in the patients receiving tenofovir FTC and there were 64 infections in people receiving placebo. This was highly statistically significant. The effect was even stronger in the patients who were compliant with the therapy.
These are very important results, and now that we have them, what are we going to do with them?[2] One of the first questions is: Who are the providers who are going to make the decisions about prescribing tenofovir FTC in someone who is at high risk of acquiring HIV infection? Will it be primary care providers? Will it be infectious disease specialists? Will it be HIV specialists? It's really not clear because a lot of these providers either don't take care of HIV-negative individuals (in the case of HIV specialists or infectious disease specialists) or they don't provide longitudinal care (such as people who specialize in treatment of sexually transmitted infections).
Another practical question is: If it is decided that people should receive this therapy, should they get it continuously like in the study? Should it be provided intermittently -- which is, anecdotally, how it's being given in the small number of people who have started doing it already even before the study results were released.
Another question is: Will this be covered by insurance plans? I don't know if there is going to be a single answer for that, but I highly suspect that this will not be covered by AIDS drug assistance programs which are already pressed for resources, especially in some states. Those plans are for treatment of individuals with HIV.
Another very important question is: What are the long-term safety issues with prescribing preexposure prophylaxis? Although this study did not demonstrate any significant toxicities -- in particular, no significant renal toxicities -- there was a little bit more nausea in the people who had the active drug. Of course, the burden of proof of safety must be a bit higher when you're using something for prevention rather than using it for actual treatment.
Those are some of the questions brought up by this exciting study.[3] I think iPrEx is really the capper on what has been a very exciting year or so of HIV prevention research. We've had the exciting data on the Thai vaccine study, which, even though not practically applicable, showed us last fall that there was at least a hope for an HIV vaccine. There was the finding from a prospective study that HIV treatment seemed to reduce the risk for transmission by 90%-plus. Then, of course, this summer was the presentation of the CAPRISA [Centre for the AIDS Programme of Research in South Africa] data demonstrating that women who used tenofovir vaginal microbicide had significant protection from acquiring HIV. Altogether, this is a very fast-moving field and a very exciting one. Stay tuned for more information on HIV prevention studies in the upcoming months. Thanks very much.
References
References
1.Grant RM, Lama JR, Anderson PL, et al, for the iPrEx Study Team. Preexposure chemoprophylaxis for HIV prevention in men who have sex with men. N Engl J Med. 2010 [Epub ahead of print].
2.Michael NL. Oral preexposure prophylaxis for HIV -- another arrow in the quiver? N Engl J Med. 2010 [Epub ahead of print].
3.Sax P. HIV and ID observations. Available at: http://blogs.jwatch.org/hiv-id-observations/ Accessed November 23, 2010.
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