Science Translational Medicine: Vaginal Ring Could Protect Women From HIV

A vaginal ring can protect monkeys from SHIV, a virus composed of genes from HIV and simian immunodeficiency virus or SIV, reports a new study in the 5 September issue of Science Translational Medicine.

The research offers the first data suggesting that packing microbicides—experimental compounds typically given in gel form that attack bacteria and viruses—inside a vaginal ring may be an effective way to deliver drugs that protect women against HIV.

The work is an early step in part of a larger strategy to develop a vaginal ring that prevents multiple sexually transmitted infections like HIV, human papillomavirus, and herpes, as well as unplanned pregnancy.

The microbicide, called MIV-150, squelches HIV infection by distorting the shape of an enzyme the virus needs to make additional copies of itself. Rachel Singer, a senior scientist at the Population Council's Center for Biomedical HIV Research, and colleagues tested intravaginal rings loaded with MIV-150 in a small group of macaque monkeys.

High levels of the drug were detected in the animals' vaginal fluids and tissues after the rings had been inserted for a month, and the researchers observed that the ring significantly protected the monkeys from SHIV infection.

The intravaginal ring developed by the Population Council is loaded with a microbicide that may have the potential to prevent HIV infection.

[Photo by Julie Sitney, courtesy of the Population Council]

“This study not only provides proof-of-concept for rings but it also expands potential microbicide options by giving us exciting new data on the efficacy of the anti-retroviral MIV-150,” said Melissa Robbiani, director of the Population Council's Center for Biomedical HIV Research and a lead researcher on the study. “As we learned here, MIV-150 is highly effective at preventing infection when released from a ring.”

Made of either ethylene vinyl acetate or silicone, the vaginal ring releases a steady stream of MIV-150 that penetrates surrounding tissues within 30 minutes after insertion. The doses used in this study were higher than would be used in women, but previous macaque studies have shown that lower doses of MIV-150 in combination with other drugs delivered in a gel will likely be effective and have broader activity against sexually transmitted infection.

Lower doses of MIV-150 alone might be effective but could lead to drug resistance issues, the researchers say. The ultimate goal is a single ring loaded with multiple drugs, which could prevent HIV as well as other sexually transmitted infections and unwanted pregnancy. Like hormone-dosed vaginal rings commonly used for contraception, women would insert the rings themselves. Ultimately, the researchers hope that women will be able to leave the device in place for up to three months before a replacement is needed.

Nadia Ramlagan

5 September 2012