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Tenofovir in plasma predicted protection from HIV
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SEATTLE – Detection of tenofovir disproxyl fumarate in plasma was strongly predictive of high protection from HIV acquisition among people who took the drug for pre-exposure prophylaxis, according to researchers from the University of Washington.
“Adherence appears to be a critical factor in achieving high protection from HIV infection using pre-exposure prophylaxis,” study researcher Deborah Donnell, PhD,of the Fred Hutchinson Cancer Research Center and the University of Washington, said during a press conference here. “We used tenofovir levels as a marker of adherence to the study medication. Generally, based on results from previous studies, we can say that if no tenofovir was detected in the plasma, then the medication had not been taken for about ten days.”
The phase 3, randomized, placebo-controlled trial included 4,758 couples that included one partner who was HIV-positive and one who was HIV-negative. The partner that was HIV-negative was randomly assigned to receive pre-exposure prophylaxis with either tenofovir alone or combination emtricitabine/tenofovir or to placebo.
In this case cohort study, the researchers examined tenofovir levels in participants who did acquire HIV and compared these levels to participants who did not acquire HIV. This study included 198 randomly selected participants from the participants who received pre-exposure prophylaxis. The plasma from months 1, 3, 6, 12, 18, 24, 30 and 36 was tested.
Twenty-nine of the participants acquired HIV. Among these participants, 35% from the tenofovir alone arm had tenofovir detected in the plasma at the seroconversion visit, and 25% from the combination arm had tenofovir detected in the plasma at the seroconversion visit. Among those who did not develop HIV, 83% of the samples from the tenofovir arm had detectable tenofovir and 81% of the samples from the combination arm had detectable tenofovir.
The median tenofovir concentrations among the uninfected cohort were 70 ng/mL for those who received only tenofovir and 67 ng/mL for those who received the combination. Among those who only received tenofovir, having detectable levels of the drug was associated with an 86% reduction in HIV risk. Among those who received the combination, having detectable levels of tenofovir was associated with a 90% reduction in HIV risk.
For more information:
- Donnell D. #30. Presented at: 19th Conference on Retroviruses and Opportunistic Infections; March 3-8, 2012; Seattle.
Disclosures: The researchers report no relevant financial disclosures.
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