According two studies in Africa, taking a daily pill containing either one or two anti-HIV drugs can reduce transmission of the virus by as much as three-quarters among heterosexual couples. This is an encouraging finding that could help focus on AIDS prevention. The results were so compelling that the larger study was halted early and the drugs given to all the participants, researchers said Wednesday.
Termed as “Partners pre-exposure prophylaxis” it could be the best thing since a vaccine is not yet available say experts. Mitchell Warren, executive director of the New York-based AIDS Vaccine Advocacy Coalition said the findings “are two more nails in the coffin of HIV.” “We are seeing similar results in different populations, and that gives us more certainty that these results are real,” he added.
A study of gay men reported in November showed that one of the drugs in the new trial could reduce the spread of HIV by as much as 70% when taken regularly by uninfected individuals. But a study released this year found that the drugs did not show a similar benefit among uninfected heterosexual women. The strength of the new findings suggests that the study involving women may have been flawed. “Our results provide clear evidence that this works in heterosexuals,” said Dr. Jared Baeten of the University of Washington, co-chair of the new study.
Kevin Frost, chief executive of amfAR, the Foundation for AIDS Research said a study released last July found that microbicides could sharply reduce HIV transmission in women and a study in HIV-positive people showed that treating the infected person intensively could reduce transmission by as much as 96%. Given those and other developments, “we find ourselves in a place where we have an extraordinary opportunity to radically alter the trajectory of the epidemic,” Frost said. “The science is in place. We could do it with the tools we have available. It's no longer a question of, can we do this? The question is, will we do it?”
One trial called “Partners PrEP” enrolled 4,758 couples in Kenya and Uganda in which one partner was HIV-positive and the other was not. A third of the uninfected participants received a daily pill containing tenofovir, a third received a daily pill containing tenofovir in combination with emtricitabine, and a third received a placebo or dummy. All couples also received condoms and counseling about how to prevent infection.
Tenofovir is marketed as Viread and the two-drug combination as Truvada by Gilead Sciences Inc. of Foster City, Calif. They are available generically in many countries for as little as 25 cents per pill, according to the World Health Organization.
By the end of May, researchers had identified 18 new infections among the group receiving Viread, 13 among those receiving Truvada and 47 among those receiving the placebo. That corresponds to a 62% reduction in transmission among those receiving Viread and a 73% reduction among those receiving Truvada.
The second trial called TDF2, sponsored by the U.S. Centers for Disease Control and Prevention, studied 1,200 healthy, sexually active males and females in Botswana. About half received Truvada and half a placebo. Among the 601 participants who took Truvada, there were nine new infections, compared with 24 among the 599 who received placebo. That amounts to a 62.6% reduction in new infections. Among those participants who took the drugs regularly, researchers observed an even greater reduction — 77.9% — in new infections.
No significant side effects were observed in either trial. “The perception is that these drugs are really toxic,” said Dr. Thomas J. Coates, an infectious diseases specialist at UCLA's Geffen School of Medicine. “They are not. The current generation is really quite safe.”
The new results are scheduled to be presented next week at the 6th International AIDS Society Conference on HIV Pathogenesis, Treatment and Prevention in Rome, but were released early.
Dr. Robert M. Grant of UC San Francisco's Gladstone Institute of Virology and Immunology speculated that the drugs might work even better in the United States than they did in Africa. People in this country “are more accustomed to using pills for prevention,” he noted, and thus more likely to take the drugs regularly.