Photo by Adek Berry/AFP/Getty Images.
A clinical trial testing a microbicide gel once hailed as a highly promising new approach to HIV prevention is being shut down early because of poor results.
The National Institutes of Health announced Friday that testing of the vaginal gel, which contains the HIV drug tenofovir, has been discontinued. The news was a blow to HIV prevention research and disappointing to the researchers hoping to offer women another way to protect themselves against the disease, aside from asking their partners to use condoms.
An early review of the data found no difference between the rate of new HIV infections among women using the gel, and women using a placebo– about 6 percent in both groups–resulting in the recommendation to shut down this part of the trial.
The results were in stark contrast with the outcome of an earlier, smaller trial released in 2010 that showed a 39 percent reduction in HIV infections among women in the study, and a 54 percent reduction among those women who used the gel with high adherence. These results were considered such a breakthrough by the attendees of the International Aids Conference in 2010, the researchers received a standing ovation.
The latest trial involved 5,000 women in Uganda, South Africa and Zimbabwe, and more frequent use of the gel on a daily basis. Researchers hoped to confirm that first promising protection data, and help clear the path for licensing through the U.S. Food and Drug Administration.
“Our thinking was that using the vaginal gel daily would provide even better coverage. We were hoping to replicate that finding and actually improve on the efficacy,” said Jeanne Marrazzo, a professor at the University of Washington and one of the principle investigators of the study. “[The results] were a huge surprise and a big disappointment.”
Instead, the data provided “clear evidence that the gel was not effective in the women in the study,” according to a statement from the Microbicide Trials Network overseeing the study.
The reason for the disparity in results is still unknown, but a full analysis of the data will be conducted after this portion of the trial is shut down. Some of the factors under consideration are whether women actually used the gel daily, if there was some connection to how close to intercourse the gel was applied, or if the HIV viral loads were just too high for the gel to combat. The high rates of STDs could also play a role, as they can contribute to new HIV infection.
The end of the three country study does not mean tenofovir microbicide is completely off the table as an HIV prevention method. Another phase three trial testing the gel is ongoing among 2,200 women in South Africa, and uses the same dosing as the original trial. Those results are expected in 2014.
“Our results make that study even more important,” said Marrazzo. “Whenever you get disparate results in two trials the best thing you can do is try to get a tie breaker.”
Women in both studies receive counseling on HIV prevention and access to condoms, as well as the gel.
Marrazzo and her team are also continuing another arm of their clinic trial, looking at daily use of an oral antiretroviral drug for prevention.
“We can’t afford to be discouraged. Even though we are devastated we can’t afford not to be creative, committed and move forward,” Marrazzo said. “These are women who are really hard hit by HIV and we have to continue.”