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03/04/2013

CROI 2013: Monthly tenofovir intravaginal ring prevents SHIV infection in female macaques


James Smith, from the Centers for Disease Control and Prevention, presented data on a novel delivery system, an intravaginal ring, for pre-exposure prophylaxis. Intravaginal rings that deliver a sustained release of tenofovir disoproxil fumarate (TDF), a highly potent prodrug of tenofovir (TFV), were investigated for efficacy in delivering adequate levels of drug in mucosal tissues and in reducing SHIV incidence among female macaques. The intravaginal rings with TDF (TDF-IVR) resulted in high concentrations of TDF and TFV in vaginal secretions (70.87 μg/mL (range 25.68-118.41) and 44.61 µg/mL (range 20.19-74.35) respectively. To investigate efficacy in reducing HIV acquisition, macaque sized TDF-IVRs were administered to 6 macaques and replaced every 28 days during a 16 week challenge period. The 6 macaques with the ring as well as 12 controls, were repeatedly exposed to SHIV once weekly for up to 16 weeks. The results were promising. All macaques that had received TDF-IVRs ring remained SHIV seronegative, while 11 of 12 untreated controls seroconverted (p <0.0004). In addition, TDF-TFV levels were detected in anal tissue. This unique delivery system may provide a feasible option for pre-exposure prophylaxis among women at risk for HIV infection, covering vaginal and possible anal sites of exposure. The monthly vaginal dosing application may also assist adherence, an issue recognized as a key area of concern among users of daily vaginal microbicides in the VOICE study.

References:
1. Smith J, Rastogi R, Teller R, Srinivasan P, Mitchell J, McNicholl J, Hendry M, Mesquita P, Kiser P, Herold B. A Tenofovir Disoproxil Fumarate Intravaginal Ring Completely Protects against Repeated SHIV Vaginal Challenge in Nonhuman Primates. Presented March 4, 2013 at the 20th CROI, Atlanta, GA. Oral Abstract 25LB.
2. Smith J, Rastogi R, Teller R, Srinivasan P, Pau C-P, McNicholl J, Hendry M, Mesquita P, Herold B, Kiser P. A Novel Intravaginal Ring Design Releasing Tenofovir Delivers Comparable Tenofovir Diphosphate Levels in Vaginal Target Cells in Macaques to Gel Dosing. Presented March 4, 2013 at the 20th CROI, Atlanta, GA. Poster Abstract 986.


Source: Reporting from Atlanta for PRN News: Anita Radix, MD, MPH