By DORSEY GRIFFITH
July 26, 2005
Costly new drugs can slow AIDS death rates and have had a huge impact in the U.S. and other countries that can afford them. But AIDS remains a dire threat in developing nations, and the great hope for a vaccine to prevent the spread of the disease is still unfulfilled.
All that has fueled a movement to develop medicines that, when applied vaginally before sexual relations, block HIV infection and other sexually transmitted diseases and, in some cases, prevent pregnancy.
Called microbicides, the products are viewed as tools for women, particularly in the developing world, to protect themselves from human immunodeficiency virus and gain more control over their sexual and reproductive health.
"The thinking is to develop a product women could control without having to negotiate with a male partner," said Ron Frezieres, research division director at the California Family Health Council, which is testing three microbicides. "With condoms, you have to negotiate their use."
Signs that the microbicide movement has gained traction are everywhere, from the microbicide lab of a tiny biotech firm in Santa Clara, Calif., to the struggling city of Chitunguiza, Zimbabwe, where women are being recruited to try one of the products.
Dozens of companies are working to come up with effective microbicides, their ideas nurtured by funding from a growing cadre of organizations, including the Bill & Melinda Gates Foundation.
A statement by a summit of the Group of Eight leading industrial countries calls for investment in microbicide development. Congress recently endorsed substantial increases in microbicide research funding.
More than 30 products are in development, and thousands of women are taking part in clinical trials of the drugs furthest along in the pipeline.
"Vaccines are the single best way to control an epidemic," explained Dr. Mark Mitchnik, chief scientific officer at the three-year-old International Partnership for Microbicides, which invests millions in promising technologies. "Over the past couple of years, as it has become obvious a vaccine is a very difficult task, microbicides have come into their own."
Unlike a vaccine, which stimulates antibodies to confer immunity against a disease, microbicides kill bacteria, viruses and other pathogens that can cause disease. While some are designed to kill a pathogen, others interfere with the microorganism's ability to attach to its target cells.
The products in development range in complexity from lime juice (believed to keep the vaginal environment inhospitable to pathogens) to nucleotide reverse transcriptase inhibitors (which inhibit the virus's ability to replicate) and "plantibodies" (human antibodies genetically engineered in corn and rice that can block disease).
Microbicides can be formulated as gels or creams and delivered with an applicator or contained in suppositories or sponges. Researchers also are exploring use of devices such as intravaginal rings that would offer protection for extended periods.
Researchers and infectious-disease specialists agree microbicides would be a welcome addition to the limited arsenal against sexually transmitted diseases.
Bethany Young Holt, an epidemiologist and coordinator of the California Microbicides Initiative, worked in the 1990s as a Peace Corps volunteer in West Africa and later in Ethiopia for the U.S. Centers for Disease Control and Prevention.
"It was apparent to me that the condoms and other interventions were completely a joke for the epidemic in Africa," she said. "You are trying to get African men to put on condoms, and they won't. And women are completely unempowered to negotiate anything. If they are sick, they can't even go to the clinic without their husband's permission."
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