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February 28, 2011

Study Shows Rectal-Specific Formulation of Tenofovir Gel is Needed

Both oral Truvada and topical 1% vaginal tenofovir have been shown to prevent HIV-1 infection, but will either safely and effectively prevent rectal infection? Peter Anton, from the David Geffen School of Medicine in Los Angeles, presented data in a late-breaker presentation at the 18th CROI in Boston, Massachusetts addressing this question. He and his group assessed the safety, acceptability, and pharmacokinetics of oral tenofovir (TDF) and rectal application of 1% vaginal tenofovir gel (TFV) as well as their efficacy in suppressing ex vivo HIV infection of rectal biopsies.

In 18 healthy subjects, who sequentially received a single dose of TDF (300 mg), a single rectal dose randomized to TFV or placebo, and randomized 7 days’ rectal dosing, both general and mucosal safety were monitored throughout the study. Ex vivo rectal biopsy infectibility and plasma drug concentrations were measured at 5 time points after oral and rectal and once after the seven-day dosing.

Based on their findings, they concluded that rectal dosing with the vaginal formulation of 1% TFV was neither entirely safe nor fully acceptable, indicating the need for development of a rectal-specific formulation of TFV for use in future rectal microbicide studies. The 7-day rectal TFV use resulted in significant inhibition of ex vivo HIV infection, suggesting that a rectal-specific formulation of TFV might inhibit rectal acquisition of HIV in vivo. In contrast, neither single oral (TDF) nor rectal (TFV) dosing significantly inhibited biopsy infection, suggesting a single pericoital use of these might not be an effective prevention strategy in reducing HIV transmission during anal intercourse.

Reference: Anton P, Cranston R, Carballo-Dieguez A, et al. RMP-02/MTN-006: A Phase 1 Placebo-controlled Trial of Rectally Applied 1% Vaginal TFV Gel with Comparison to Oral TDF. Presented Feruary 28, 2011, at the 18th Conference on Retroviruses and Opportunistic Infections; Boston, MA. Oral Abstract 34LB.

Source: Reporting from Boston for PRN News: James F Braun, DO