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and Hepatitis.com Coverage of the
18th Conference on Retroviruses and
Opportunistic Infections (CROI 2011)
February 27 - March 2, 2011, Boston, MA
Safety and Acceptability of Tenofovir Gel and Tablets for Pre-exposure Prevention
An experimental vaginal gel containing a 1% concentration of tenofovir is being studied to prevent HIV transmission. Tenofovir (included in the Truvada and Atripla coformulations) is widely used as part of combination antiretroviral therapy for the treatment of HIV infection.
In an oral presentation at CROI, Craig Hendrix from Johns Hopkins University described an open-label crossover study comparing the 1% vaginal gel versus oral tenofovir in 144 HIV negative women in Africa and the U.S.
Women in the study used the pill alone, the gel alone, and the pill and gel together (dual regimen) each for 6 weeks. The women served as their own controls in the study, using the 3 regimens in a randomized order.
looked at pharmacokinetic parameters (drug levels), markers of adherence,
and product acceptability of the 3 regimens.
The researchers concluded that both tenofovir formulations were equally safe and tolerable, and that expected differences were seen in drug concentrations in plasma and vaginal tissues based on drug delivery system.
Further, they saw significant differences between African and American women in terms of acceptability of the formulations. These findings, Hendrix said, suggest that multiple formulations should be available so products can match varying preferences.
Rectal Use of Tenofovir Gel
In another oral presentation at CROI, Peter Anton from the University of California Los Angeles described a study of the safety, pharmacokinetics, and acceptability of 1% tenofovir vaginal gel when used rectally.
included 18 participants, of whom 78% were male and 22% female. Participants
were given an initial single oral dose of tenofovir in pill form. They
were then randomized in a 2:1 fashion to receive either placebo gel
or 1% tenofovir gel, first as a single dose followed by 7-day dosing;
2 week washout periods followed each dosing. Multiple pharmacokinetic
and tissue samples were collected for 2 weeks following each dosing.
The researchers concluded that the 1% tenofovir gel formulation was "sub-optimal in terms of safety," but most study participants said they would use the product again "if it were found to be useful."
As expected, drug concentrations in the rectal tissue were significantly higher with the gel than the pill, while the opposite was true in plasma. Anton said they are now working on a gel formulation with lower osmolarity, which may reduce lower GI side effects.
C Hendrix, A Minnis, V Guddera, and others. MTN-001: A Phase 2 Cross-over Study of Daily Oral and Vaginal TFV in Healthy, Sexually Active Women Results in Significantly Different Product Acceptability and Vaginal Tissue Drug Concentrations. 18th Conference on Retroviruses and Opportunistic Infections. Boston. February 27-March 2, 2011. Abstract 35LB.
R Cranston, A Carballo-Dieguez, and others. RMP-02/MTN-006: A Phase
1 Placebo-controlled Trial of Rectally Applied 1% Vaginal TFV Gel with
Comparison to Oral TDF. 18th Conference on Retroviruses and Opportunistic
Infections. Boston. February 27-March 2, 2011. Abstract