ROME — A pill a day prevents transmission of HIV among heterosexual men and women, a researcher said here.
In preliminary results from a randomized controlled trial in Botswana, men and women who got an anti-HIV medication saw their relative risk of HIV reduced by 62.6% compared with those who got placebo, according to Michael Thigpen, MD, of the CDC.
The medication — a single-pill combination of tenofovir and emtricitabine (Truvada) — was also safe and well-tolerated, Thigpen said at the 2011 conference of the International AIDS Society.
The finding comes after an earlier study of so-called pre-exposure prophylaxis, or PrEP — this one among men who have sex with men — showed the same medication reduced the risk of infection.
■Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
■Explain that in this study, a pill a day containing a combination of tenofovir and emtricitabine (Truvada) prevented transmission of HIV among heterosexual men and women.
■Note that those receiving the study drugs reported significantly more adverse events than those in the placebo group, a difference driven by increased rates of nausea and vomiting.
And it comes as another study, also presented here, showed a similar result among men and women in so-called discordant couples — those in which one partner has HIV and the other does not.
“This is a really exciting time in HIV prevention,” Thigpen told MedPage Today. There is now “little doubt about the power of anti-retroviral-based HIV prevention strategies,” he added.
The so-called TDF2 study analyzed rates of HIV infection among 1,200 uninfected men and women in Botswana, more than 93% of them single — in contrast to other studies in couples. As in all such trials, participants got a package of services intended to increase their awareness of HIV and reduce their risk of infection, including access to condoms and counselling about safe sex.
After more than two years of follow-up, there were nine HIV infections among those getting the study drug and 24 in the placebo group, yielding an overall protective efficacy of 62.6%, Thigpen said. The result was “strongly significant” at P=0.0133, he said.
The result was even more striking when the researchers restricted their analysis to participants who became infected while they were on the study drug or within 30 days of their last dose, Thigpen said.
In that group, he said, there were four infections in the active group and 19 among those getting placebo, for a protective efficacy rate of 77.9%, which was significant at P=0.0053.
One participant in the drug arm — who had an unrecognized HIV infection at baseline — developed high-level resistance to the study drugs, Thigpen said. One participant on the placebo arm developed low-level resistance, he said.
Those getting the study drugs reported significantly more adverse events (at P=0.019) than those in the placebo group, a difference driven by increased rates of nausea and vomiting — 18.8% versus 7.2% and 11.5% versus 6.8%, respectively.
On the other hand, there were no differences in the number of abnormal laboratory values by treatment group, Thigpen reported.
There were also no differences in treatment adherence, estimated by pill count, or in reported sexual behavior, the researchers found.
The study, along with others presented here, represents an “unprecedented opportunity to expand the toolkit for prevention,” said Gottfried Hirnschall, MD, head of the World Health Organization’s HIV department in Geneva.
Hirnschall said the United Nations agency had wanted to launch new guidelines here on care for discordant couples, but has pulled them back for more work after the two new studies presented here.
And he cautioned there remains “a treatment gap of nine million people” who need HIV therapy but are not getting it.
But Stefano Vella, MD, of Italy’s Istituto Superiore di Sanita and a conference co-chair, said getting treatment to those people is no longer a matter of “humanitarian aid.”
In the light of the recent research, Vella told reporters, “this is a real investment” in slowing and perhaps halting the HIV/AIDS pandemic.
Despite the positive PrEP results, several experts said there is still some concern over the halted FEM-PrEP study, which was testing tenofovir/emtricitabine as PrEP in women in three African countries.
The study was stopped earlier this year when an interim analysis revealed similar numbers of HIV infection in both the placebo and drug arms, with little likelihood that would change.
“It’s important not to forget about that and consider it a fluke,” said Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases. He called for further “serious studies” to see why the FEM-PrEP trial did not work as well as others.
The study was supported by the CDC and the National Institutes of Health.