Tamar Kahn
29 January 2008
Johannesburg — RESEARCHERS around the country are anxiously awaiting the results of the Carraguard microbicide trial, a large-scale study involving more than 6000 South African women.
It is intended to demonstrate that a seaweed-based vaginal gel offers some protection against the human immunodeficiency virus (HIV).
It is the only microbicide study so far to have reached the end of a phase 3 trial, the last stage of research before companies can register a product with regulatory authorities and begin marketing it.
Although resources have been poured into microbicide research worldwide in recent years, none of the candidate products worked. Interest in the Carraguard study, the results of which are expected next month, is therefore especially keen.
In 2000, advanced research into a microbicide containing the spermicide nonoxynol-9 was stopped after it was found to do more harm than good. Last year's studies of the efficacy of a product based on cellulose sulphate were stopped on similar grounds.
Even a microbicide that turns out to be only partially effective against HIV would be a valuable addition to the scant arsenal against the virus. At present, only condoms offer reliable protection against sexual transmission of HIV, says Smruti Patel, one of the study's principal investigators.
A microbicide could also prove to be a life-saving alternative to condoms in situations where people refuse to use them, says her co-investigator Alana de Kock. In SA alone, more than 5,5-million people were infected with HIV, and young women were at particularly high risk.
"Regardless of how much information these women have, at the end of the day they depend on their men putting on a condom," says De Kock.
Carraguard contains carrageenan, a seaweed derivative that has been classed as generally safe for human consumption by the US Food and Drug Administration. Carrageenan has a long history in the food and cosmetics industry. It is used to thicken ice cream and baby food, and gives skin creams an slippery texture, says Dr Sumen Govender of the Population Council, one of the study's sponsors. Other funders include the Bill and Melinda Gates Foundation and USAID.
Laboratory and animal tests have already demonstrated that Carraguard acts as a mechanical barrier against HIV, and stops the virus entering the mucosal cells lining the vagina.
Studies on human volunteers in six countries, including the US, SA and Thailand, showed the product was safe and well tolerated by both women and men before scientists began enrolling volunteers for the final stage of the research , conducted in SA .
SA was chosen because the research had to be done among HIV-negative women who were at high risk of getting the disease, which meant working in a community with a high background incidence of the disease, says De Kock. Sites were selected in Gugulethu, Soshanguve and Isipingo, all communities with high HIV prevalence.
In Gugulethu for example, 28,8% of women attending ante-natal clinics in 2006 were HIV positive.
The women were divided into two groups, with half getting the microbicide gel and half getting a dummy version that appeared identical. Neither the researchers nor the volunteers knew which arm of the trial the women belonged to.
The volunteers were given regular counselling, and advised to use condoms and the gel every time they had sex, since no one knew whether they were getting the candidate product or the placebo, or indeed whether the candidate product would work, says De Kock. The women used a small plastic applicator to insert about a teaspoon of the clear, odourless gel into their vagina up to an hour before they had sex.
If it turns out that Carraguard is indeed effective against HIV, much must still be done before it finds a spot on pharmacy shelves. If an effective product is to have a significant effect on the HIV epidemic, it will have to be swiftly registered by the authorities and manufactured at an affordable price, says Govender.
Whether or not the trial results are what they hope to hear, De Kock and her colleagues believe the work they have done to teach women about their reproductive health has been a worthy undertaking in its own right.
The volunteers were screened for cervical cancer, HIV and other sexually transmitted infections, and treated.
They were also counselled.
"The women came in quite ignorant about their own bodies, and are now much more educated. Women have also improved their communication about HIV and have got their partners to start using condoms," she says .
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It is incorrect to suggest that the cellulose sulphate trials were stopped on similar grounds to the previously halted Nonoxynol-9 trial - that was found to do more harm than good. By saying this, you imply that cellulose sulphate is known to do more harm than good which is incorrect. There is no evidence at all to suggest that cellulose sulphate is at all harmful and in fact, in over a decade of human studies cellulose sulphate consistently demonstrated a very strong safety profile. Yes, there were HIV sero-conversions within the cellulose sulphate trials that were unexpected, and with the safety of the women participants being the paramount concern, the trials were stopped immediately with the notion that it was better to err on the side of caution and safety until more was known about the HIV conversions within the trial. Further analysis showed that these conversions "were not statistically significant" and no evidence was presented to explain why one site had more HIV conversions than other sites within the trial. No further evidence has yet become available, and in varying African press there were reports that some participants were selling their compound and not strictly adhering to the trial protocol. This also has not been proven, but in the absence of evidence for either case, neither can be said or implied as the reason the trials were halted.