All trials of oral PrEP so far (other than small safety trials
of experimental drugs) have involved taking either Truvada (tenofovir/emtricitabine) or tenofovir alone once a day.
The French researchers wanted to see if taking PrEP only around the time
participants were actually exposed to HIV would work too. The primary reasons
for doing this would be to see if adherence was better, and also to save money,
as PrEP’s per-unit cost is far higher than other prevention methods such as
condoms. Intermittent dosing could also lower the risk of side-effects. Animal
studies had shown that intermittent PrEP might work.
In Ipergay, gay men and other men and transgender women who have
sex with men, and were at high risk of HIV infection, were asked to take two Truvada pills (or a placebo) from
one day to two hours before they anticipated having sex. If they actually did
have sex, then they were to take another pill 24 hours after having sex and a
fourth pill 48 hours after it. The period of taking PrEP would thus cover two
to three days. If they continued having sex, they were told to continue taking
PrEP until 48 hours after their last experience.
As in PROUD, all participants also received risk-reduction
counselling, were provided with condoms, had three-monthly tests for HIV and
other sexually transmitted infections (STIs), and received hepatitis A and B
vaccines if needed.
Ipergay started enrolling participants in February 2012. Like
PROUD, it was intended to be a pilot study demonstrating the feasibility of its
approach and the investigators initially planned to recruit 350 participants.
By November 2014, it had in fact recruited exactly 400
participants who were actually given Truvada
or placebo. Altogether 445 people came forward, but 14 (3.1%) were found to
have acute HIV infection when they were screened or on randomisation and 31 others left the study for various reasons (e.g. not meeting eligibility criteria, or lost to follow up). Thus four hundred people are included in this analysis, though in fact
by de-randomisation in November, 47 participants had withdrawn or disappeared, and the number in the study at this point was 353.
The average age of participants was 35, 95% were of white
ethnicity, 90% had competed secondary education, only 21% had a primary relationship,
and 20% were circumcised. Forty-six per cent had used methamphetamine, amphetamine,
GHB/GBL, cocaine or ecstasy in the last year. At baseline, 25.5% had been
diagnosed with gonorrhoea, chlamydia or syphilis in the last year.
The average number of sexual partners participants had had in
the previous two months was eight. Seventy per cent had had condomless anal sex
in the previous two months. A proportion – 28% in the Truvada arm and 37% in the placebo arm – had used post-exposure
prophylaxis (PEP) before.