Trial finds tenofovir gel safe for daily use and most women adhered to study regimens

Results of Phase II study of ARV-based microbicide presented at international meeting in India bolster interest in latest approach

NEW DELHI, Feb. 25, 2008 – A vaginal microbicide that incorporates an antiretroviral (ARV) drug normally used to treat people with HIV is safe for sexually active HIV-negative women to use every day over an extended period, suggest results of a clinical trial of tenofovir topical gel. Moreover, most of the women who participated in the study conducted in India and the United States adhered to a regimen involving either daily or sex-dependent use of the gel, report researchers from the U.S. National Institutes of Health-funded Microbicide Trials Network (MTN) at Microbicides 2008, an international meeting taking place Feb. 24-26 at the Hotel Ashok in New Delhi.

The findings, presented today for the first time, are a significant boost to HIV prevention efforts focused on the potential of "next-generation" microbicides to curb infection rates in women. Globally, nearly half of those living with HIV/AIDS are women, and between 70 and 90 percent of all HIV infections in women are due to heterosexual intercourse. In India and many other parts of the world, even married women and women with steady partners are at risk.

In this Phase II study, called HPTN 059, researchers wanted to understand if tenofovir was safe to use every day for six months compared to its use prior to each act of sex, and if women were able to adhere, or follow, each regimen. Researchers found both approaches equally safe and women’s adherence to product use similar. Interestingly, most participants also said they would be willing to apply gel, including daily, if one were found effective to prevent against getting HIV from their sexual partners.

Microbicides are products designed to prevent the sexual transmission of HIV when applied topically on the inside of the vagina or rectum. Tenofovir gel is among a newer class of candidate microbicides that differ from early types because they have specific action against HIV. In addition, because tenofovir gel and similar products are longer acting, their use may not be required before each act of sex, which is not always practical or desirable for some women.

“Finding that daily use is both safe and feasible is important because we believe a daily approach may provide more sustainable protection against the virus in women who can’t always predict when they will have sex. Based on what we have learned we can proceed with greater confidence on a path that will answer whether tenofovir gel and other gels with HIV-specific compounds will be able to prevent sexual transmission of HIV in women when other approaches have failed to do so. It is a critical time for all of us engaged in HIV prevention, and I truly believe we are turning a corner,” said Sharon L. Hillier, Ph.D., professor and vice chair for faculty affairs, and director of reproductive infectious disease research in the department of obstetrics, gynecology and reproductive sciences at the University of Pittsburgh School of Medicine, who is MTN principal investigator and led the study.