[Viva] Fwd: CATIE News - PrEP reduces HIV transmission for heterosexual men and women

[Denise Becker]

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From: <mailing at mercury.catie.ca>
Date: Thu, Aug 4, 2011 at 6:47 AM
Subject: CATIE News - PrEP reduces HIV transmission for heterosexual men and
women
To: dbecker106 at gmail.com


*CATIE News - PrEP reduces HIV transmission for heterosexual men and women*

Pre-exposure prophylaxis, or PrEP, is currently being studied as a potential
method for a person who is at risk of HIV infection to reduce their risk of
becoming infected. It involves taking anti-HIV medications on a regular
basis.

Earlier this year, a study called iPrEx, found that an anti-HIV pill
(tenofovir + FTC, called Truvada) taken daily reduced the risk of HIV
infection when used by men who have sex with men. Surprisingly, a few months
later, a study called FEM-PrEP was closed early because daily tenofovir +
FTC *did not* seem to reduce the risk of HIV infection among heterosexual
women. Based on the preliminary data, it is not clear why PrEP did not work
for women in the FEM-PrEP study.

Preliminary results from two new PrEP studies, known as TDF2 and Partners
PrEP, were announced early in July 2011 and additional data were presented
at the IAS conference in Rome. Both of these studies suggest that PrEP *does
* work for HIV-negative heterosexual women and men.
TDF2 Study

The TDF2 study enrolled 1,219 HIV-negative heterosexual men and women from
Botswana. Nearly half (46%) of the participants were women.

Half of the participants were asked to take a daily pill (Truvada,
containing two anti-HIV drugs: tenofovir + FTC). The other half were asked
to take a daily placebo. Participants returned to the study site every month
to receive their pills.
Results—effectiveness

During the study, 33 of the participants became infected with HIV. The HIV
infections were distributed as follows:

   - Daily tenofovir + FTC – 9 infections (7 in women, 2 in men)
   - Daily placebo – 24 infections (14 in women, 10 in men)

Based on these numbers, participants using tenofovir + FTC were 63% less
likely to become infected with HIV than participants using a placebo. This
finding was statistically significant.

A separate analysis looked at whether tenofovir + FTC provided similar
levels of protection for both men and women. The analysis found that
tenofovir + FTC reduced the risk of HIV infection by 80% for men and by 49%
for women. Although it appears that PrEP was less protective for women, the
study was not large enough to draw firm conclusions about the effectiveness
of Truvada by gender.
Results—adherence and safety

Adherence to taking a pill every day was relatively high. By counting the
number of leftover pills, researchers estimated that the overall adherence
rate was approximately 84%.

Daily Truvada was well tolerated. Participants taking Truvada experienced
slightly higher rates of nausea, dizziness and vomiting than those taking a
placebo. All the reported symptoms were mild.

Only one participant developed drug resistance during the study. This person
had acute HIV infection when they enrolled in the study and was therefore
HIV-positive when starting PrEP. Of the participants who were HIV-negative
when starting PrEP and later became infected, none developed drug
resistance.
Partners PrEP

The Partners PrEP study enrolled 4,758 heterosexual serodiscordant couples
(one partner in each couple was HIV-negative and the other positive) in
Uganda and Kenya. Nearly 40% of the HIV-negative partners were female. None
of the HIV-positive partners were eligible for ART according to their
country’s treatment guidelines at the time of enrolment.

The HIV-negative partners were assigned to one of three groups: One group
was asked to take a tenofovir (Viread) pill daily; one group took a pill
containing tenofovir + FTC (Truvada) daily; and one group took a placebo
pill daily.
Results—effectiveness

The couples were followed for an average of 1.7 years. A total of 78 of the
HIV-negative partners became infected with HIV during this time. The number
of HIV infections in each group was as follows:

   - tenofovir – 18 infections (8 in women, 10 in men)
   - tenofovir + FTC – 13 infections (9 in women, 4 in men)
   - placebo – 47 infections (25 in women, 22 in men)

Overall, tenofovir taken alone reduced the relative risk of HIV infection by
62% and tenofovir + FTC reduced the relative risk of infection by 73%. Both
of these findings were statistically significant. Although it seemed that
tenofovir + FTC provided more protection than tenofovir alone, this
difference in rates of protection was not statistically significant.

A separate analysis was performed to determine if PrEP benefited both
genders. The analysis found that PrEP was beneficial for *both* men and
women. Tenofovir alone reduced the risk of infection by 55% among men and
68% among women while the combination of tenofovir + FTC reduced the risk of
infection by 83% among men and 62% among women. Unlike the TDF2 study, the
Partners PrEP study was large enough for researchers to make definite
conclusions about the effectiveness in different genders. All these findings
were statistically significant.
Results—adherence and safety

In this study, the adherence rate was extremely high: approximately 97%. The
adherence rate was assessed by counting the leftover pills that participants
returned to the study team. This was higher than the adherence rate observed
in other PrEP studies, such as iPrEx and TDF2.

Unlike these other studies, Partners PrEP only enrolled serodiscordant
couples who were in stable relationships. It’s possible that being in a
relationship helped the HIV-negative partner adhere to their pill-taking
schedule.

Both PrEP regimens were well-tolerated and did not cause any major side
effects. The participants who took anti-HIV drugs reported slightly higher
rates of mild nausea and diarrhea than those taking a placebo. These side
effects were more commonly reported during the first month after starting
PrEP and decreased afterwards. Information on drug resistance has not been
released.
Summary

Both the TDF2 and Partners PrEP studies strongly suggest that oral PrEP is
safe and effective when used by heterosexual men and women. In contrast to
the findings from the FEM-PrEP study, both of these studies suggest that
PrEP *does* work for women. Further analysis is needed to explain the
FEM-PrEP results.

An ongoing PrEP study, called VOICE, will provide more information about the
effectiveness of PrEP among women. This study is enrolling heterosexual
women and investigating the use of three different PrEP regimens: (1) daily
tenofovir, (2) daily tenofovir + FTC, and (3) daily application of a vaginal
gel containing tenofovir.

It is important to note that all participants in these trials, whether they
were taking PrEP or a placebo, were provided with a comprehensive package of
prevention services. This included risk-reduction counselling, adherence
counselling, diagnosis and treatment of sexually transmitted infections, and
free male and female condoms. These studies demonstrate how many additional
infections are prevented when PrEP is added to a comprehensive approach to
HIV prevention. PrEP may be less effective if provided in the absence of
these services.

The TDF2 and Partners PrEP studies are ongoing although the provision of a
placebo pill has been discontinued. After the release of the preliminary
results, all participants were offered the option to remain in the study and
use PrEP to reduce their risk of infection. These types of studies are
commonly called “roll-over” or “open-label” studies. These studies will
provide important information on adherence and risk-taking behaviours among
men and women who know that the pills they are taking are effective.
PrEP resources:

CATIE *Prevention in Focus* article on
PrEP<http://www2.catie.ca/en/pif/february-2011/preparing-pre-exposure-prophylaxis>
CATIE fact sheet on
PrEP<http://www.catie.ca/facts.nsf/9a83231f2055bda9852566b90004b064/63fa080d951d80558525782d005e0a8d!OpenDocument>
CATIE News story on iPrEx
trial<http://www.catie.ca/catienews.nsf/00a48c8905294f0b8525717f00661eb8/ee5fd5a40d7375c3852577e6005cec31!OpenDocument>
CATIE News story on FEM-PrEP trial
<http://www.catie.ca/catienews.nsf/00a48c8905294f0b8525717f00661eb8/c91fd34dbc9f29b48525787f0057eea8!OpenDocument>

*References*

   1. Baeten J. *Antiretroviral pre-exposure prophylaxis for HIV-1
   prevention among heterosexual African men and women: the Partners PrEP
   Study. *Sixth International AIDS Society Conference on HIV Pathogenesis,
   Treatment and Prevention, Rome, abstract MOAX0106, 2011.
   2. Thigpen M, Kebaabetswe PM, Smith DK et al. *Daily oral antiretroviral
   use for the prevention of HIV infection in heterosexually active young
   adults in Botswana: results from the TDF2 Study.* Sixth International
   AIDS Society Conference on HIV Pathogenesis, Treatment and Prevention, Rome,
   abstract WELBC01.



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