The Partners Pre-Exposure Prophylaxis study involved heterosexual couples from Kenya and Uganda. One partner in each of the 4,758 couples enrolled was HIV positive.
The HIV negative partners were randomly assigned to once-daily tenofovir (Viread), a combination of emtricitabine/tenofovir (Truvada), or placebo, and followed monthly for up to 36 months. Tenofovir and emtricitabine slow the spread of HIV in the body by blocking an enzyme necessary for viral production. Both are usually prescribed in combination with other HIV medications.
Study co-author Kenneth H. Fife, M.D., Ph.D., professor of medicine, of microbiology and immunology, and of pathology and laboratory medicine at the Indiana University School of Medicine, said, “The two drugs are widely used for HIV treatment and are very well tolerated, but this is the first time they have been used for HIV negative patients. This study is significant because it provides physicians with a new tool for HIV prevention.”
The clinical study was stopped early because of the effectiveness of the medications.
After 23 months, 82 individuals who were HIV negative at the start of the study contracted the virus. Of those, 17 were assigned tenofovir alone; 13 were randomized to the emtricitabine/tenofovir combination, and 52 were assigned placebo. This translates into a risk reduction of 67 percent for tenofovir and 75 percent for the emtricitabine/ tenofovir combination.
“Previously, people could use condoms and reduce their number of sexual partners as a deterrence to HIV transmission; now this is another option,” Dr. Fife said. He cautioned that compliance with taking the medication was a key factor in the favorable results.
“It’s not clear how long these anti-retrovirals should be used by healthy individuals,” he said. “As with all medications, there are risks involved, including reduced kidney function, although that was not seen as a significant problem in our study.”
Other co-authors of the study who participated with the IU School of Medicine research include Edwin Were, M.D., and study coordinator Cosmas Apaka, both from Eldoret, Kenya. The IU-Eldoret team enrolled and followed 488 couples during the study.
An application has been submitted and approval has been recommended by the FDA advisory committee for use of the two anti-retroviral drugs for preventing HIV in people at risk. The FDA has not acted on the recommendation.