A New HIV-Blocking Gel Could Replace Condoms

A new, more-promising iteration of the long-heralded HIV-blocking vaginal gel may one day become a reality, according to a study published online yesterday in the journal Advanced Functional Materials. But as the dream product crawls towards the marketplace, scientists worry that the biggest challenge—getting women to actually use it, or any gel like it—still lies ahead.

Unlike previous versions of microbicide, the latest gel functions more like an actual condom. It's applied via applicator in the hour or so before sex and turns semisolid in the presence of semen, physically blocking HIV (and theoretically, other viruses and semen, too) from moving through the vagina in the first place. (The gel dissolves after sex.) "It's the first microbicide of its kind," says Patrick Kiser, a bioengineer at the University of Utah and the study's lead author. "It prevents the virus from even touching the vaginal tissue." The novel polymer concoction could see its first clinical trial in three years and if all goes well, be available for widespread use a few years after that.

The need for HIV-prevention methods that women can control is undeniably urgent. Women account for half of all HIV infections globally; in sub-Saharan Africa, where the disease is most prevalent, they make up 60 percent of cases. The reason is simple: women in the region lack the power to compel their sexual partners to wear condoms. For a decade now, scientists have been working to develop an HIV-blocking vaginal gel, a microbicide often called a molecular condom. This form of protection could be employed without the consent of a partner and has long been seen as the best hope for empowering women to protect themselves.

But, like any effort to bring high-tech innovation to resource-poor settings, progress has been slow. In 2007, one large-scale clinical trial was terminated early when the substance—cellulose sulphate—appeared to actually increase the risk of HIV infection. Another early contender, developed in an American lab, failed to hold up in the warmer African climate (it turned from a usable gel into a messy ineffective liquid). And Carraguard, a gel derived from seaweed extract, made it all the way to phase III clinical trials only to be abandoned late last year when results showed that it was not effective at preventing HIV: the gel was safe, but its difficult to say how well it worked because study participants only used it 40 percent of the time.

The failure underscored what has become a common complaint among some factions of global health workers: high-tech solutions that come from Western labs often fail to account for on-the-ground realities. "There are numerous personal and cultural reasons why a microbicide may or may not be used," says Kate Morrow, a behavioral psychologist at Brown University who has collaborated with Kiser. Failure to consider those factors may have doomed some projects from the start.

In the case of Carraguard, it's not clear exactly what went wrong, but David Katz, a biomedical engineer and gynecology professor at Duke University thinks the effort to design a molecular condom has been plagued from the start by a lack of intellectual diversity. "It's a tough problem because sex is complicated, messy, and differs culturally in surprising ways," he says. "Microbicide research has been dominated by virologists, but if you really want to solve the problem, you need engineers and psychologists, as well."

In an effort to design a more appealing and culturally acceptable product, Katz, Kiser, and their colleagues have turned to some even more unlikely sources. "We've looked at food science," he says. "It turns out that an extraordinary amount of research goes into the feel of ice cream—not just what it tastes like, but what it feels like in our mouths—so we borrowed some of their rationale."

Namely, the idea that texture and consistency matter. "If it leaks during sex, or if it feels unnatural, it will impact a woman's decision to use it," says Morrow. In collaboration with Katz and Kiser, Morrow has spent time surveying microbicide-study participants in the sub-Saharan region. Many women worry that an unnatural feel will drive their partners away, she says. While Morrow has collaborated with Kiser on the latest gel, it remains to be seen how it will fare among the women of Africa, where an effective HIV prevention mechanism for women is most urgently needed.

A longer-acting gel that could be applied hours before sex would also be a plus. Kiser's polymer gel is only effective for a few hours, but he says he is currently working on a longer-acting version of the product. In the meantime, other researchers are at work on a ring version of the HIV-blocking gel, that could be inserted into the vagina and left there, like the birth-control rings that have been popular in the West.

Whatever form it arrives in, the molecular condom promises to be one of the most valuable weapons yet in the fight against AIDS. "The more we learn about HIV, the more we think we may never be able to cure it," says Katz. " Vaccines have not panned out so far, and condoms aren't used enough, but ultimately, prevention will be the key to everything."