Scientists have announced that a new type of contraceptive gel that is also designed to protect against sexually transmitted infections will be the first of its kind to begin clinical efficacy trials at the National Institutes of Health's Contraceptive Clinical Trials Network.

The gel, known by the brand name BufferGel^TM, was developed jointly by researchers at Johns Hopkins and the private firm ReProtect LLC. The new trial will test whether women using BufferGel and a diaphragm can reduce the risk of pregnancy as effectively as women using a conventional spermicidal detergent and a diaphragm.

BufferGel is applied vaginally before sex, like conventional spermicides. Unlike these spermicides, which use detergents to kill sperm, BufferGel contains no soaps, which can irritate the vaginal lining after frequent use.

"BufferGel simply reinforces the mild acidity that occurs in the vagina naturally," says developer Richard Cone, a professor of biophysics in the Krieger School of Arts and Sciences.

"The normal acidity levels in the vagina can readily kill sperm and many of the germs that cause sexually transmitted infections," explains Cone, who also is managing director of ReProtect. "That's why your stomach's contents are acidic. Most germs just don't survive long in acidic environments."

Semen eliminates vaginal acidity for several hours to allow sperm to leave the vagina and enter the uterus. Unfortunately, this also can help make it possible for germs to infect the sexual partner. Cone says BufferGel should block this effect, killing both sperm and germs by rapidly acidifying semen.

While reinforcing the vagina's natural acidity seemed like a simple enough approach for developing a contraceptive microbicide, several practical considerations made developing a useful compound challenging, according to Cone.

"Not only must the compound kill both sperm and germs, it must do so without hurting the friendly bacteria in a healthy vagina, like the lactobacilli," he explains. Also, the compound must not irritate sensitive tissues or be offensive to the user or her partner.

BufferGel has met those standards in both animal trials and extensive clinical safety trials, according to Cone.

For the new contraceptive efficacy trial, researchers at 10 sites in the United States are enrolling 1,000 women. Participants in the study must be in a sexually active and monogamous relationship and at low risk for infection by sexually transmitted diseases. They must agree not to use other forms of contraception beyond that supplied by the study, and be willing to risk getting pregnant. Study participants will use a diaphragm with either BufferGel or a conventional spermicide.

"In this trial, we want to achieve the highest possible level of protection," says Thomas Moench, medical director for ReProtect and a former assistant professor of infectious diseases in the School of Medicine, who created BufferGel with Cone. "We're including a diaphragm because it places a discrete physical barrier over the cervix, significantly enhancing the protective actions of contraceptive microbicides."

Hopkins and ReProtect LLC are developing BufferGel through a cooperative research agreement.

Researchers also are planning a larger trial to test BufferGel's ability to block transmission of HIV and genital herpes. The trial is scheduled to take place through NIH's HIV Prevention Trials Network next year.