adminNew microbicide products could turn the tide against Aids for those who need it most: women in sub-Saharan Africa. Dinsa Sachan reports women, and particularly those in sub-Saharan Africa, lack options to protect themselves against HIV. HIV/Aids poses a huge threat around the world: 35 million people live with the disease, while around 1,5 million people die from it every year. And that is in spite of new HIV infections falling by 33 percent since 2001 due to the availability of anti-retroviral drugs.
An Aids vaccine appears to be a long shot at the moment. So in the meantime, scientists are keenly looking at other options that could prevent HIV.
Among these are a class of compounds called microbicides. These can be applied at the site of infection in the form of gels or rings. Most of these products are currently targeting women. Given the speed with which developments are taking place in this field, a microbicide could be in the market as early as 2018, opening a new chapter in the fight against the disease.
Why microbicides?
When it comes to options for HIV prevention, women don’t get a level playing field. First off, there aren’t too many prevention options available to them. Condoms and male circumcision are only of use to men. The anti-retroviral pill, Truvada (tenofovir/emtricitabine, is approved for use in prevention in the US, but other countries haven’t allowed it for use in HIV-negative individuals.
Moreover, in sub-Saharan Africa, which has one of the worst HIV epidemics, women are often not able to get their partners to use condoms.
“Women need discrete methods that are under their control, ideally from a choice of HIV prevention products that match their needs,” says Connie Celum, professor of allergy and infectious disease and reproductive sciences at the University of Washington in the US. Celum and colleagues are trying to turn the tables for women through microbicides.
Apart from empowering women from a socio-economic perspective, microbicides hold certain medical advantages, too.
“With microbicides, we put a lot of drug at the site of infection, but there are low levels in the blood, which means there’s less toxicity to the bones, to kidneys and it doesn’t have systemic side effects,” says Sharon Hillier, professor of obstetrics-gynecology at the University of Pittsburgh, US.
Hillier is co-chair of the Microbicide Trials Network (MTN), an HIV/Aids clinical trials network established in 2006 by the US National Institutes of Health.
“It doesn’t give you an upset stomach, for example, as sometimes anti-retroviral tablets can do,” she adds.
This property could also make microbicides potentially safe for pregnant women and women who are breastfeeding. If microbicides become available one day, they are, however, not expected to replace the condom.
“Microbicides are one tool in one large toolkit,” says Zeda Rosenberg, head of the International Partnership for Microbicides, a non-profit initiative dedicated to microbicide research.
“It’s like how we have multiple contraceptive options for women.”
Early candidates fail
When Aids was first reported in the US in 1981, it was thought that it only affected gay men. However, when the scientists realised later that women were getting it too through vaginal sex, they focused their attention on developing a prevention strategy solely targeting women. Today, half of the people living with HIV/Aids in the world are women. The number goes up to around 60 percent in sub-Saharan Africa.
The first product that was put on trial was an over-the-counter contraceptive called nonoxynol-9, or N-9, the main ingredient of many spermicidal products. It kills sperm by attacking their cell membranes.
The compound shows anti-HIV properties in the lab, but it didn’t quite succeed in clinical studies as a vaginal gel. In fact, some researchers found that N-9 actually harmed the vaginal mucosa, increasing the risk of infection. In 2001, the WHO concluded that research on N-9 should be discontinued.
Another approach was investigated based on the observation that low pH could inactivate HIV. So acid-buffering gels were used to lower vaginal pH and inactivate HIV. Though this was a relatively safe approach, it wasn’t potent enough to prevent infection.
The scientists also tried long-chain, polyanionic compounds. In the lab, these compounds restricted entry of HIV into target cells. But they didn’t fare any better in clinical trials.
“These were non-specific strategies, and they weren’t specifically targeting the HIV virus,” says Hillier.
“Simply put, they were kind of impotent.”
New phase, but new challenges
After the first nondescript phase in the hunt for a microbicide ended, scientists decided to shift their focus to anti-retroviral drugs. These drugs had a successful track record in treating the HIV/Aids epidemic. They targeted the HIV virus specifically so they seemed to stand a better chance. But commercial success still seems to be elusive. – Online.
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