Microbicides: Stopping the spread of HIV/AIDS

 

AIDS has been around now for over 25 years, and although treatment options have advanced considerably in that time, prevention options are still few and often considered cum­bersome. Considering that it will cost $12 billion annually to provide treatment to the 40,000 new HIV cases in the United States each year, it is clear that the accelerating rate of new infections globally is far out-pacing potential treatment pro­grams and is unsustainable.

 

In the past decade, we have seen the burden of AIDS shift largely to women who are becoming infected from their hus­bands, whose work often takes them on the road and where infidelities are sometimes a culturally divined right. Women and girls are learning that to save their own lives they need access to some form of protection that does not rely on a man's willingness to wear a condom. And some women in developing countries have adopted a female condom prod­uct that did not sell very well in the developed world.

 

To provide women with another, more discreet method of protection, microbicides are being developed that could offer protection many hours in advance of, or just prior to a sexual encounter, and may even be undetectable by her part­ner. Microbicides have several different mechanisms. Some act by killing pathogens, like antibiotics do, while others block transmission by forming a barrier between the patho­gen and healthy cells or block early steps in the infectious process, preventing the pathogen from replicating.

 

Microbicides are being developed in a variety of forms including gels, films, rings and suppositories, and different compounds will offer women the choice of contraceptive or non-contraceptive protection. The field is so excited about the potential for microbicides that promising second-gen­eration microbicides, combination compounds and shared technology uses are already under study, with emerging candidates in early clinical trials.

 

The first-generation microbicides, currently involved in late-stage clinical trials, are crucial to the evolution of new prevention technologies. Even a partially effective first-generation microbicide can prevent several million new infections in the earliest years of availability, and can pre­pare the way for advancing candidates. The Population Council is evaluating data from a recently completed efficacy trial of Carraguard, a seaweed-based microbicide. Indevus Pharmaceuticals' PRO2000, an agent that disrupts viruses, and ReProtect's Buffergel, a pH buffer, are engaged in sepa­rate and combined late-stage clinical trials to determine effectiveness.

 

For its part, Polydex Pharmaceuticals developed Ushercell in collaboration with the research team at CONRAD, a pro­gram of the Eastern Virginia Medical School. Currently in Phase III trials, Ushercell is a clear, odorless gel made from simple cotton fibers. Its exceptional safety profile makes it an ideal candidate for advanced research in first- and next-generation compounds.

 

Emerging technologies such as an HIV vaccine and other prevention research will explore the safety of pre-exposure prophylactic regimens and next-generation microbicides combining technologies or mechanisms-of-action.

 

A safe and effective microbicide could have a substantial impact in decelerating the spread of HIV and AIDS, which has claimed over 40 million lives since it was first detected in 1981. Another 40 million people are currently infected with HIV and a daunting proportion of those infected are com­pletely unaware of their status.

 

It is important to recognize that microbicide research will require years of continued funding and advanced clinical tri­als to keep the development pipeline on the path of success. UN Envoy Stephen Lewis reminds us to remain diligent in our work, saying that the "search for a microbicide is one of the most important things the world is doing."

 

No single strategy or technology will solve the AIDS pandemic. We must employ all existing prevention strate­gies, such as behavior change, counseling and testing, STD diagnosis and treatment, broad access to male and female condoms, and anti-retroviral interventions. We must also focus on expanding our repertoire of tools and technolo­gies, and microbicides will likely be available sooner than an HIV vaccine. And even after a safe and effective vaccine is discovered, vaccines and microbicides will have different, complementary roles to play in an integrated, multi-faceted global HIV prevention strategy.