VIENNA, Austria | In a big step forward for the field of HIV prevention, a new study shows for the first time a microbicide gel provided significant protection for women from HIV infection.
Use of a vaginal gel containing the drug tenofovir before and after sex reduced acquisition of HIV by 39 percent among the women participating in the South-African-based study, and by 54 percent among those women who used the gel with high adherence.
The researchers also found the gel provided a 51 percent reduction in herpes infection.
The results of the study are in the journal Science this week and were presented Tuesday to a packed audience and a standing ovation at the 2010 International AIDS Conference in Vienna.
An effective microbicide has long been sought in the fight against HIV because it could be used discreetly by women, without the knowledge or consent of their partners, unlike condoms.
“It’s the first time in the history of the disease that a study has been conducted that would give control [of HIV prevention] to young women,” South Africa’s Health Minister Aaron Motsoaledi said.
The study took place in KwaZulu-Natal, South Africa and included 889 women, half of whom were given a placebo gel.
While the tenofovir results do not provide complete protection, one of the study authors, Quarraisha Karim, said the efficacy level that was found is still a milestone in prevention.
“With microbicides, we have to look at the 39 percent in relation to what do we have to offer women who are at risk of getting infected,” Karim said. “We are comparing 39 percent to nothing.”
It’s also the first time a microbicide has provided an “unequivocally significant” level of protection for women from HIV, said Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases at the U.S. National Institutes of Health.
He expressed confidence that the level of protection provided by the gel could be improved in future studies, either through changes in dosing, application or by combining it with other drugs.
“We should look at this as a celebration but also as a beginning … of something we know we can do better on,” Fauci said.
Prior to the tenofovir results, the field of HIV microbicides had seen trial after trial in the past 15 years end in frustration, including several previous candidates co-author Salim Karim (pictured here) investigated.
“I did several of the other studies so I’ve had to deal with the disappointment at every turn,” Karim said. He attributes the new study’s success to the fact that tenofovir does not work on the surface of the skin like past candidate microbicides.
“[Tenofovir] goes into cells, into the target cells where HIV will be targeting to enter and replicate so it acts at a different point in the pathogenesis process,” Karim said.
It is also the first antiretroviral-based microbicide to go into trials, said Yasmin Halima, director of the Global Campaign for Microbicides.
“It’s a really good result- it’s the first result really,” she said. “You have to — as robust as the data is — have another trial. We have to replicate and improve it; we need to see if we can up the 39 percent.”
Karim agreed and said he still has questions about how exactly the drug is working in the body.
“I think the challenge for us lies in better understanding the biological basis of why some women became infected despite tenofovir,” Karim said. “The second, and probably bigger challenge, is to try to improve the adherence.”
The study cost $17.6 million — $16.5 million of which came from USAID and the remaining funds from South Africa’s Technology Innovation Agency.
The microbicide will not be available for use in the near future because it still needs to be licensed and approved by regulatory authorities. Karim said the World Health Organization and UNAIDS will be consulting with regulators in the coming weeks to find out what specific information still needs to be acquired for the product to progress.
Individual countries will decide on approval based on the strength of the study, the country’s disease burden and other factors. Fauci called it “doubtful” that the U.S. FDA would approve the product at this point because of the size of the initial tenofovir study and the level of protection found, but said additional data from future studies could strengthen the evidence.
“That doesn’t take away from the fact that this is unquestionably a conceptual major advance,” he said.