December 12, 2006

Gel Condom to Prevent HIV

(AIDSmeds.com)—Utah scientists are designing a "molecular condom" to prevent HIV infection in women. It is a vaginally inserted liquid that turns into a gel-like coating and then, when exposed to semen, returns to liquid form and releases an infection-stopping antiviral drug. Development of the new microbicide was announced in a December 11 research paper published on the Journal of Pharmaceutical Sciences' website.

"We have developed a new vaginal gel that we call a molecular condom because it is composed of molecules that are liquid at room temperature and, when applied in the vagina, will spread and turn into a gel and effectively coat the tissue," says Patrick Kiser, PhD, an assistant professor of bioengineering at the University of Utah. "It's a smart molecular condom because we designed this gel to release anti-HIV drugs when the gel comes into contact with semen during intercourse."

The molecular condom is part of a worldwide research effort to develop microbicides: drug-delivery systems such as gels, rings, sponges, or creams designed to prevent infection with HIV and other sexually transmitted infections. Microbicides are seen as a way for women to gain power by protecting themselves from HIV, particularly in impoverished nations where AIDS is widespread, where rape is rampant or where conventional condoms are taboo, not reliably available, or where men resist using them.

About 16 microbicides are in development and five are undergoing testing in thousands of women, mostly in Africa. They are designed to fight HIV infection by preventing the virus from entering cells or replicating, or by maintaining acidic vaginal conditions.

The first-generation microbicides are expected to be available within four years. Studies completed thus far suggest that they will be 50% to 60% effective. While this may sound unimpressive, a British study has suggested that a microbicide that is only 50% effective and used by only 20% of the women in 73 developing nations would have a net effect of preventing 2.5 million infections during a three-year period. Dr. Kiser says he hopes the molecular condom ultimately will prove to be 90% effective.

Dr. Kiser suggests that his group's molecular condom would be a more advanced method of delivering an antiviral drug to prevent HIV infection. "Up until now, most of the microbicide work has focused on the development of the active drug, not on the delivery of the drug," he says. "This study and other work in my lab are directed at developing new technologies for vaginal delivery of antiviral agents, particularly a microbicide that can respond to triggers," such as body temperature and semen, "that are present before, during and after intercourse. This is the first paper that begins to point in that direction."

Dr. Kiser says the dosage of anti-HIV drugs in first-generation microbicides lasts only a few hours, so "you have to use them an hour before sex, which is difficult. You only need one failure to get the disease. We're shooting for a microbicide delivery system that would be used once a day or once a month."

In the study, Dr. Kiser and colleagues outline how they designed a water-based gel or "hydrogel" sensitive to body temperature and pH (acidity or alkalinity) so that it could serve as a "smart semen-triggered vaginal microbicidal vehicle."

The researchers have not yet tried incorporating an HIV drug into the hydrogel. However, in laboratory tests involving mock drugs, the hydrogel succeeded in turning from a liquid to a gel at body temperature, followed by a return to liquid and the release of the mock drug when exposed to semen.

Potential side effects of microbicides include itching, increased vaginal discharge, and inflammation. But initial testing of the molecular condom – in which the hydrogel was tested on basic tissue cells known as mouse fibroblasts – "indicates these gels are likely to be well tolerated," Dr. Kiser says.

Dr. Kiser and his University of Utah colleagues hope to incorporate experimental HIV entry inhibitors into the molecular condom.

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