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| |  Breakthrough Tenofovir Microbicide Gel Reduces HIV Transmission: Presented at AIDS 2010 By Evelyn Harvey VIENNA -- July 20, 2010 -- A novel vaginal gel containing tenofovir significantly reduces HIV infection, and represents the first effective antiretroviral microbicide for use by women, researchers said here on July 19 at the 18th International AIDS Conference. The Centre for the AIDS Programme of Research in South Africa (CAPRISA) 004 trial showed that the tenofovir gel reduced HIV incidence by 39%, with no drug-related adverse effects. Salim Abdul-Karim, of CAPRISA, Congella, South Africa, and colleagues randomised 889 women aged 18 to 40 years who were sexually active but uninfected with HIV to receive a hydroxyethylcellulose (HEC) gel containing tenofovir 40 mg (n = 445) or an HEC placebo gel (n = 444). Gels were supplied in prefilled vaginal applicators. Following in-depth consultation prior to the study, a pre- and postcoital dosing strategy was used: participants were advised to apply the gel within 12 hours before sex and within 12 hours afterwards. No more than 2 doses per 24-hour period were recommended, due to a lack of safety data. Participants were tested for HIV and pregnancy every month for 30 months and comprehensive HIV-prevention counselling was given to all women. The tenofovir gel arm had an HIV incidence rate of 5.6 per 100 woman-years (38 cases), compared with 9.1 per 100 woman-years in the placebo group (60 cases; P = .017). Infection rates declined over time in the placebo group, from 11.2 to 9.1 per 100 woman-years, but remained constant at <6.0 per 100 woman-years in the tenofovir group. After adjustment for baseline variables including condom use, age, and herpes simplex virus-2 antibodies, the hazard ratio for tenofovir treatment was 0.63 (P = .025). Adherence was calculated on the basis of reported sexual acts and numbers of used applicators returned. Women using the tenofovir preparation had high adherence (>80%) and a 54% reduction in HIV acquisition (P = .025), compared with the placebo arm. Those with intermediate (50% to 80%) or low (<50%) adherence showed decreases in infection of 38% and 28%, respectively. Pregnancy rates were similar between groups, and no congenital abnormalities were detected. In the women who contracted HIV, no resistance mutations to tenofovir were detected. There was also no evidence suggesting that tenofovir gel masked HIV infection in these women. The CAPRISA 004 results offer the first hope that women may be able to protect themselves from HIV infection even when unable to negotiate condom use or monogamy. The trial offers proof that an ARV-based vaginal gel can prevent HIV transmission safely and effectively. "We've been waiting for this moment for 2 decades," said Dr. Karim. '"But we need to find out why it didn't work in some women and find avenues to do better." He added that adherence would be an important factor in determining efficacy. Funding for this study was provided by CAPRISA, USAID, and Gilead Sciences. [Presentation title: Safety of 1% Tenofovir Vaginal Microbicide Gel in South African Women: Results of the CAPRISA 004 Trial. Abstract TUSS0503]
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