A trial to evaluate an anti-HIV microbicide cream for women has found the product is safe, but it was not able to prove it could prevent male to female transmission of the virus during sex. However, researchers said it was a milestone in the fight to prevent the spread of HIV.

The cream is called Carraguard and is made from carrageenan seaweed. The US Food and Drug Administration (FDA) have given it a “Generally Recognized As Safe” go ahead for oral and topical use.

Carraguard is the first product designed to be a microbicide that has completed the final phase of clinical testing. The trial found it to be safe for vaginal use, but it did not show it was effective at stopping the virus passing from a man to a woman during vaginal intercourse.

The randomized, double blind, phase 3 trial involved 6,202 women and was carried out at three South African sites where the HIV epidemic is acute. It started in March 2004 and finished in March 2007.

The women were equally split into a Carraguard group and a placebo group. Both groups received a topical gel and condoms, and neither participants nor their doctors knew who got the Carraguard and who got the placebo (double blind). All participants also received education about HIV, counselling about safe sex and how to reduce risk of sexually transmitted infections, as well as being medically examined, and tested and treated for curable sexually transmitted infections.

The results showed 134 new infections in the group that used Carraguard and 151 in the placebo group. This translates to an incidence rate of 3.3 infections per 100 woman-years compared to 3.7, respectively, a difference that was not found to be statistically significant.

The researchers found no safety related differences between the placebo and the active ingredient group, and adverse events due to gel application were minor and infrequent.

The researchers said this result was important because of what it means to the development of the next generation of microbicides, of which Carraguard is an important ingredient.

President of the Population Council, Peter Donaldson, said:

“We are disappointed that this trial did not show Carraguard to be effective.”

But, he added that the completion of the trial marked a “milestone in HIV prevention research”. It has made a big contribution to knowledge about product development, trial design, and the willingness of women and their partners to use a vaginal gel consistently, said Donaldson. The data will be very useful to other researchers working on microbicides.

Director of the Population Council’s HIV and AIDS program, Naomi Rutenberg, said:

“The Population Council will use these trial results to accelerate the development of effective means for women to protect themselves against HIV.”

In the laboratory, Carraguard was found to be effective at stopping cells from invasion by HIV, and it also stopped mice getting some sexually transmitted infections. Carraguard and similar products based on carrageenan seaweed have been tested widely in trials in the US, Australia, Chile, the Dominican Republic, Finland, South Africa and Thailand, in over 850 men and women.

The US Agency for International Development (USAID) and the Bill & Melinda Gates Foundation funded the trial. Speaking for USAID, their senior science advisor, Jeff Spieler said they always knew it would take a long time to produce a successful microbicide:

“The Population Council has done groundbreaking work in completing this trial, even though we are terribly disappointed that the product was not shown to be effective,” said Spieler.

“Now we all have to redouble our efforts to develop a microbicide that women can use to protect themselves,” he urged.

Developing effective vaginal microbicides is important because it gives women more options for controlling the spread of HIV and other sexually transmitted infections, especially since current strategies are not always possible.

Click here for more information about the Population Council.

Click here to learn more about microbicides from the Alliance for Microbicide Development.

Source: Population Council press release.

Written by: Catharine Paddock, PhD