Scientists at Hopkins have created a new type of
contraceptive gel for women that may not only prevent pregnancy,
but also sexually transmitted diseases, including AIDS.
The approach is a departure from conventional birth control methods. It works by maintaining the mild, protective acidity in the vagina--an acidity normally canceled out by semen during intercourse. Acidity kills sperm and microbes, such as the viruses and bacteria that cause many sexually transmitted diseases.
After three years of research, the gel has been selected for clinical trials by the National Institutes of Health. NIH also has awarded nearly $2 million to finance further work on the gel, developed by biophysics professor Richard Cone, Thomas Moench, a former assistant professor of medicine, and reproductive biologist Kevin Whaley, a research scientist in biophysics and an adjunct faculty member in the School of Hygiene and Public Health.
The gel is a vaginal microbicide; in addition to killing sperm and microbes, laboratory research has shown that it also destroys white blood cells in sperm and cervical mucous that can be infected with the human immunodeficiency virus. The infected sperm and mucous act as biological "Trojan horses," traveling between sexual partners and transmitting the virus, Cone said.
The experimental contraceptive may be marketed after undergoing extensive tests over the next two years.
One problem with conventional spermicides and contraceptives is that they have to be applied shortly before sex, making them less than desirable for couples in the heat of the moment.
"It's across the room in a drawer," said Nancy Alexander, chief of the Contraceptive Development Branch at NIH's Center for Population Research. If a spermicide could be applied in the morning, during the course of routine daily hygiene, and still be effective that night, more women would use it more often, she noted.
Another problem with spermicides now on the market is that they are detergents, such as Nonoxynol-9, which increase the risk of urinary tract infections in women.
Better, more convenient contraceptives for women are critically needed, Alexander said. More than half of all pregnancies in the United States are unintended, and roughly 1.6 million of the 6.4 million women who become pregnant annually end up having abortions.
Despite the growing need for better birth control methods for women, there have been few breakthroughs in the field since the 1960s, when the pill and intrauterine devices were introduced. While the pill has led to more advanced hormonal contraceptives in recent years, those methods do nothing to prevent sexually transmitted diseases.
The next generation of birth control products should do more than prevent unwanted pregnancies; they should safeguard against the transmission of diseases during rectal, as well as vaginal, sex, Alexander said. The gel, which its creators call BufferGel, is one of several promising experimental contraceptives being tested.
Although the concept of blocking the alkalinizing action of semen may seem intuitively simple, in practice it has proved to be a daunting challenge. For years other scientists had pursued a logical, but fruitless, approach: they tried to make spermicides from the same acids already present in the vagina, acetic acid and lactic acid. But those acids, if delivered at high enough concentration to be effective, become toxic. At such elevated concentrations, the acid molecules can penetrate cells in the mucosa--the lining of the vagina--possibly damaging the cells and causing irritation.
"I think the acidic approach had pretty much been abandoned by the time we got interested in it," Moench said.
For an acidic microbicide to be effective, it must neither harm the cells of the vaginal lining, nor kill the beneficial bacteria in the vagina, such as lactobacilli. In fact, those bacteria help create the protective acidity in the first place by producing lactic acid.
It was clear what the job called for: an "acidic buffer," a mildly acidic gel that would not damage the cells, Moench said.
Such a buffer would have to be a polymer, or a long chain of molecules, that would be unable to penetrate the membranes of beneficial cells, rendering the buffer harmless to those cells. At the same time, it would maintain the mild acidity, killing sperm and microbes that are sensitive to acid, including those that cause syphilis, gonorrhea, genital herpes and HIV.
Tailoring a new polymer to do the job, and proving its safety, could have taken years. But the Hopkins researchers found a shortcut.
They learned that the potential ingredients for a buffering gel already were being used in some products; the materials are called gel-forming agents, which make runny liquids into useful lubricants. Moench, Whaley and Cone then began experimenting with the chemicals, formulating a contraceptive gel that has the same mildly acidic level as the vagina, pH 4--comparable to the acidity of strawberry jam.
One hope is that further research could result in a contraceptive gel lasting for 24 hours or longer. The scientists are developing ways to boost the gel's effectiveness by incorporating antibodies and vaccines. Antibodies are secreted naturally by the mucosa, but additional antibodies that attack specific microbes could be used to heighten that natural defense, the Hopkins researchers said.
To develop and market the gel, the three scientists founded a private company, ReProtect LLC. They also have formed a long-term research-and-development agreement with a New York-based company, Ultrafem Inc. Through the agreement, the two companies will produce a series of products, including a vaginal cup, which will be used to cover the cervix much like a diaphragm. The gel could be delivered directly to the vagina with the cup, or applied alone.
Go back to Previous Page