Two large studies of pre-exposure prophylaxis – use of
antiretroviral drugs by uninfected people to prevent HIV infection – have shown that taking
tenofovir or tenofovir plus emtricitabine (Truvada)
can cut the risk of HIV infection through sexual transmission by between 62% and 78% in male-female couples.
from both the Partners study and the TDF2 study were released today.
“This study demonstrates that
antiretrovirals are a highly potent and fundamental cornerstone for HIV
prevention and should become an integral part of global efforts for HIV
prevention,” said Dr Connie Celum, Professor of Global Health and Medicine at the
University of Washington,
The results, released this morning ahead of the
International AIDS Society (IAS) conference in Rome
next week, follow positive results from the IPrEX study of Truvada PrEP in men who have sex with men released in November 2010.
Fuller results from the studies will be presented next week.
The Partners study took place in Kenya
It recruited 4,758 male-female couples in which one partner was HIV-positive.
The uninfected partners were randomised to receive either tenofovir, tenofovir
plus emtricitabine (Truvada) or a
placebo. The medication was taken daily, and all participants received
counselling on safer sex, both individually and as a couple, and received free
condoms and monitoring and treatment for sexually transmitted infections.
The study was halted more than 18 months early after an
interim review of the data found a highly significant effect of PrEP.
The risk of infection was reduced by 62% in those who
received tenofovir alone (95% confidence interval 34% - 78%, p=0.0003), and by
73% in those who received Truvada (95%
CI 49% - 85%; p<0.0001). The difference in protection was not signficantly
different between the two PrEP regimens, nor was there any significant difference
in protection between men and women.
Seventy-eight infections were recorded: 18 in the tenofovir
group, 13 in the Truvada group, and
47 in the placebo group.
Adherence was very high; more than 97% of doses dispensed
were taken, and 95% of participants stayed in the study.
The investigators say that rates of serious adverse events
were similar across the three study arms.
“This is an extremely exciting
finding for the field of HIV prevention. Now, more than ever, the priority for
HIV prevention research must be on how to deliver successful prevention
strategies, like PrEP, to populations in greatest need,” said Dr. Jared Baeten,
co-chair of the study and a UW associate professor of global health and
The Partners study was funded by the
Bill and Melinda Gates Foundation.
the TDF2 study, conducted in Botswana,
1,200 men and women (55% men) were enrolled and randomised to receive either Truvada
or placebo. Overall, Truvada reduced the risk of infection by 63%.
this primary analysis there were nine HIV infections amongst the 601
participants who received Truvada and
24 among the 599 who received placebo. This translates into a statistically
significant 62.6% reduction in infections.
secondary analysis, however, excluded infections that occurred amongst people who
had run out of their Truvada/placebo
pills and who had not taken one for at least 30 days. This found 77.9% fewer
infections in people taking Truvada.
results analysing efficacy by gender and other characteristics will be
announced at the IAS Conference.
TDF2 study was run by the US Centers for Disease Control in partnership with
the Botswana Ministry of Health.
The results of the two studies stand in contrast to the
decision to halt the FEM PrEP
trial, after researchers concluded that the study would not be able to show
that Truvada PrEP was effective in
preventing HIV infection in women in South Africa, Kenya and Tanzania, even if
it went on to its planned conclusion.
In that study adherence was lower, although the precise
levels of adherence have still to be presented. The FEM PrEP study also found a
higher rate of pregnancies in the Truvada
recipients, a result that was not replicated in the Partners study.
IPrEX study showed that use of Truvada reduced the risk of HIV
infection by 44%, but reduced the risk of infection among men who took it more
than 90% of the time by 73%.