Vaginal microbicides: What does the future hold?

Key Points

Our goal here is to review the various microbicides currently being tested, outlining their mechanism of action, potential usefulness, and safety profile.

A spermicide with little or no microbicidal properties

Unfortunately research proved the agent less than ideal.³ Beginning in 1990, randomized controlled trials compared different N-9 formulations-sponge, film, and various gels-and dosages^3-7 for their efficacy against HIV and other STDs. Taken together, these studies showed little if any protection against HIV, gonorrhea, and chlamydia. In one trial, women who used N-9 gel actually had higher rates of HIV than women using placebo gel.⁸

How do microbicides work?

Another polyanion gel-Pro2000/5-is currently being evaluated in large-scale effectiveness trials, which should have evidence within a year. The higher dose arm (2%) of Pro2000/5 was halted in February because the data could not show it was effective. The lower dose (0.5%) is continuing to be evaluated in two separate trials. Pro2000/5 may also have contraceptive activity. Another potential group of contraceptives, dendrimers, such as VivaGel, are highly branched macromolecules that also prevent HIV from attaching to the target cells.¹⁰ VivaGel is currently in safety studies.

While polyanions are nonspecific in the way they work, several HIV-specific entry/fusion inhibitors are also in development as microbicides, including drugs that block gp-41 fusions and CCR5-receptor binding.