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Microbicides - a weapon for women
Dr Polly F. Harrison The Economist, 28 Feb 2002. Reprinted courtesy of Gender-AIDS 2002 (e-mail: [email protected])
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In the sexual politics of AIDS, the balance of power is too often tilted towards men. Short of abstinence, the only reliable way of stopping the spread of HIV, the virus that causes the disease, is by using a condom. Despite attempts to craft versions of this device that can be worn by women, condoms are largely a male prerogative. If a man won't wear one, there is not much a woman can do to protect herself, short of outright refusal of his advances. And that is not always the preferred option.
One solution might be a vaginal microbicide that a woman would apply in anticipation of intercourse. This would either kill the virus, or block its entry into the body (not strictly a microbicidal action, but the term is still used). Over the past few weeks the Rockefeller Foundation and the Population Council, both based in New York, and the British government's Department for International Development (DFID), have launched co-ordinated initiatives designed to step up research and funding for such microbicides.
The Rockefeller Foundation's contribution was to publish, on February 15th, the results of studies begun in June 2000 to assess the feasibility of microbicides. The foundation concluded that a workable product could reach the market as early as 2007, and could stop 2.5m new infections in the first three years.
Money, however, is needed to make it past the first hurdles of development, since no big pharmaceutical companies have yet chipped in with serious investments. One of the goals of the new initiative is to prove to "big pharma" that microbicides could generate a big enough demand, and thus be worthy of the $500m investment that the foundation reckons it would need to bring a product to market. The Rockefeller thinks that the annual market for such a product would be worth $900m by 2011.
The leading candidate at the moment is Carraguard, developed by the Rockefeller-affiliated Population Council. Carraguard is the proprietary name of a substance made from carrageenan, a carbohydrate gel derived from seaweeds that is widely used as a stabiliser in the food industry. Carrageenan contains large negatively charged molecules called sulphated polysaccharides. It is believed that their strong electric charges attract them either to the viruses (thus inactivating them) or to the cells of the vaginal wall (thus covering those cells like a coat of paint and preventing viruses from entering the body). Tests on animals suggest that the substance may offer similar protection against other venereal diseases, including herpes, gonorrhoea and genital warts.
The Population Council has run small safety trials of Carraguard over the past couple of years. On February 2nd, it announced that it was organising a full-scale clinical trial of the stuff in South Africa.
This trial, which will involve 6,000 women, is to be paid for in part by the Gates Foundation (which is chipping in $20m) and is due to start later this year.
Carraguard has several things going for it. First, carrageenan is already known to America's Food and Drug Administration. The FDA has classified it as "generally recognised as safe", its highest safety rating. Second, Carraguard has shown no harmful effects in the early human trials. This was a relief, after attempts to make a microbicide out of nonoxynol-9-a spermicide commonly employed in association with condoms-revealed that frequent use made HIV infection more, rather than less, likely. Besides killing sperm and viruses, it turned out that nonoxynol-9 kills vaginal-wall cells, causing ulceration and thus giving the virus an entry-point.
Carraguard's third advantage is that it is not a spermicide. Besides offering greater choice to couples who want children, that should eliminate the religious objection that has dogged condoms: that they are a "dual-use" technology, protecting against conception as well as
infection.
Meanwhile, on February 19th, DFID announced that it was sponsoring, to the tune of A316m ($22.5m), research into Emmelle and Pro-2000-two other microbicides that work in a way similar to Carraguard. These substances are behind Carraguard in the development pipeline, though both have undergone small-scale trials. DFID plans to pay for Britain's Medical Research Council and Imperial College, London, to conduct further, larger trials in collaboration with local research institutes in Cameroon, South Africa, Tanzania, Uganda and Zimbabwe. Proving a medical invention and deploying it are, of course, two entirely different things. But a safe microbicide would be an important weapon in the anti-AIDS arsenal.
Polly F. Harrison, PhD
Director, Alliance for Microbicide Development
8701 Georgia Avenue - Suite 804
Silver Spring, MD 20912, USA
Tel 301-588-8091
Fax 301-588-8390
[email protected] |
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