2004 ANNUAL REPORT

Microbicides
Developing and Testing a Gel to Prevent HIV Transmission

Women urgently need products that they can use to protect themselves from HIV infection. The majority of new HIV infections are transmitted through heterosexual intercourse; in sub-Saharan Africa almost 60 percent of persons infected with HIV are women.

Existing strategies for preventing the transmission of HIV/AIDS—abstinence, mutual monogamy between HIV-negative partners, condom use, and treatment of sexually transmitted infections (which can facilitate HIV transmission)—are not feasible for many women. Microbicides are products, in the form of gels, foams, or creams, that might substantially reduce the transmission of HIV when applied vaginally prior to sex. The Population Council is testing its candidate vaginal microbicide, Carraguard^®, among women in South Africa. The randomized, double-blind, placebo-controlled efficacy trial of Carraguard gel began in March 2004 and will eventually enroll more than 6,000 women. The microbicide, among the first to enter efficacy trials, has already undergone extensive safety and toxicology evaluations. In the efficacy trial in South Africa, the Council is collaborating with the University of Cape Town in Gugulethu; the University of Limpopo/MEDUNSA campus in Soshanguve, near Pretoria; and the Medical Research Council in Isipingo, near Durban.

The laboratory of Population Council virologist David Phillips, which developed Carraguard, is also working on second-generation microbicides. Although the basis for these formulations is Carraguard, other agents are added to enhance its properties. In one such product, an antiretroviral drug, MIV-150, turns Carraguard into an anti-HIV cocktail. Drug cocktails have a greater chance of defeating HIV because they attack the virus through multiple mechanisms. MIV-150 inactivates an enzyme that HIV needs in order to replicate itself, while Carraguard acts as a physical barrier to infection, inhibiting viral binding to cells of the vagina. Council biomedical researchers expect to begin Phase 1 safety trials of this product in mid-2005.

Because many women who want to protect themselves from HIV would also like to become pregnant, Carraguard was originally developed to be noncontraceptive. Régine L. Sitruk-Ware, the Council’s executive director of product research and development, is overseeing the clinical testing of a contraceptive version of Carraguard developed by the Phillips lab. Robin Maguire, in the Phillips lab, proposed the contraceptive microbicide. The new, contraceptive version of Carraguard contains the progestin levonorgestrel. This microbicide is now in Phase 1 trials. Preliminary findings indicate that levonorgestrel may be absorbed by the body in sufficient amounts to be useful as an on-demand contraceptive, thus providing protection against both pregnancy and HIV infection. Currently, condoms are the only product known to offer such dual protection.

(return to 2004 Annual Report contents)

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See Also

• "Microbicides," program description (full text)

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