A report delivered at the 2014 international Conference on AIDSsimultaneously published in The Lancet Infectious Diseases July 22said that use of Pre-Exposure Prophylaxis, or PrEP, can reduce chances of HIV infection by 90%, even when the patient takes as few as four doses a week.
Strict adherence to a daily regimen of PrEP, usually taken in oral form as the drug Truvada in the United States, has been one of the central components to the therapy. Expecting such adherence from individuals taking Truvada has been regarded by health advocates, researchers and medical professionals as among the key obstacles to the drug's widespread implementation.
Robert M. Grant, MPH, of University of California at San Francisco, San Francisco AIDS Foundation and Gladstone Institutes, and colleagues were authors of the study, known as the iPrEX Open-Label Extension. Sponsored by the U.S. Institutes of Health, it focused on PrEP uptake ( whether a participant chose to take the medication ) and adherence, as well as sexual practices amongst 1,603 gay men and transgender women who have sex with men, many of whom were perceived to be at high risk for HIV infection.
Though the findings about the missed doses suggest the efficacy of Truvada, researchers nevertheless were not left with a clear picture for new dosing strategies, so persons taking Truvada will have to keep using it daily for now.
"It is inadvisable to interpret these findings in a way that encourages less-than-daily dosing at the present," wrote researchers Raphael Landovitz and Thomas J. Coates in comments published alongside the findings.
In a statement, Grant said, "Daily dosing of PrEP is recommended, because it helps foster the habit of consistent PrEP use and increases drug levels in the body, providing the best safety cushion for individuals who occasionally miss doses. At the same time, these results demonstrate that PrEP remains highly effective, even in real-world circumstances in which adherence may not be perfect."
Among other results of the study were a high uptake of PrEP when logistical barriers to it were eliminated; a gradual dropping-off of adherence amongst younger study subjects; and little evidence of risk compensation while the subjects were taking PrEP, meaning that the perceived safety of the medication did not automatically lead them to engage in condomless receptive sexual behavior or other sex practices perceived as unsafe. The authors noted however that participants who chose not to take PrEPthe study's total uptake was 76%also did not show a propensity towards risk compensation. All participants received counseling on risk minimizing strategies.
Landovitz and Coates note that subjects were also mostly participants in a previous trial, thus biasing the results to reflect a motivated population. "We eagerly await the upcoming results from a cadre of open-label studies in which tenofovir and emtricitabine [which are combined to make Truvada] is being provided to people who have not previously participated in pivotal randomized studies.
"The future is rich with possibility, but we have far to go to realize the full potential of PrEP," added Landovitz and Coates.