There has been good news this month. The Pope changed 2000
years of Catholic doctrine by saying condom use might under certain circumstances be OK, because it preserves life
rather than prevents it. The director of UNAIDS said the world has “turned the
corner” and the number of people with HIV globally is falling.
But the news that excited the most debate came from the
iPrEx study, which showed it may be feasible to use anti-HIV drugs to prevent
HIV as well as to treat it.1
iPrEx stands for,
translated out of Spanish, the pre-exposure prophylaxis (PrEP) initiative. The study
took 2500 mainly young gay men, most of them South American, who were at high
risk of HIV infection, and gave half of them a two-drug HIV pill (Truvada) and half of them a placebo. The
HIV infection rate in the men on Truvada was
nearly halved: the drugs cut the chance of acquiring HIV by 44%.
But the results get complicated, and because of this reactions to the study
have ranged from ecstatic to sceptical.
studies had suggested that PrEP could be a lot more effective than this. In
fact it was, it appeared, in people who took all their pills. Based on what
participants said and the number of pills dispensed, the researchers calculated
Truvada stopped nearly three-quarters
of infections (73% efficacy) in people who took more than nine-in-ten doses.
So far, so
good: if we could improve adherence, PrEP might be very effective. That
shouldn’t be too hard, they thought, because it looked like only one-in-ten
doses was being forgotten.
the researchers had another, more objective measure of adherence. They looked
at the 34 people who became infected with HIV while supposedly taking Truvada. They found very few of them
showed evidence of really having taken it. Good news in a way: few who actually
took the drugs got HIV.
had a shock when they looked at drug levels in people who had not become infected. They could only
find evidence of the drugs in half of them. The tests used could detect drugs
up to a month after the last dose, so this was not due to the occasional missed
dose. Not only were half of the men not actually taking their pills, four out
of five of those were lying about it.
Why were they not taking the drugs? One reason may be the
side-effect of mild nausea some reported in the first month. Something you might
live with if the pills were saving your life, but perhaps enough to put you off
if you were gambling on not getting HIV anyway.
Another hint came from interviews exploring participants’ experience
of the trial. Some said they’d found the badgering to take the pills became
oppressive after a while. For a peaceful life, 40% said they were taking pills
when they weren’t.
ways, this is very exciting news. It means the ‘true’ efficacy of PrEP might be
double that observed, and indeed the researchers calculated that if people took
all their pills all the time, Truvada
could prevent 19 out of every 20 infections. Impressive: actually better than
the rate achieved by people trying to use condoms every time.
In other ways, it’s not so good. If we can’t improve
adherence, then PrEP becomes another frustrating, not-quite-good-enough new
prevention method, like the tenofovir microbicide gel (39% efficacy in the
PrEP will only become a real option if it’s very effective
indeed. A single dose of Truvada
costs $38 a day at the US
list price – and even at the discounted rates offered to developing countries, one
pill costs 20 to 30 times as much as a condom. It’s going to have to be pretty
effective to persuade healthcare funders to pay for it.
During a conference call about the trial, Peruvian trial
director Javier Lama revealed that while iPrEx was taking place, Truvada had been unavailable to people
who needed it for treatment in Peru (though its two constituent drugs had been).
The Global Network of People living with HIV (GNP+) pointed out that during
screening for the trial, 410 men were found to have HIV, not to mention the 110
who tested positive during it. Will they get the drugs they need?
Although welcoming the trial in general, some activists were
concerned that PrEP might divert funds away from HIV treatment, and raised other
issues too. What if it encouraged people to self-medicate with HIV drugs? What
if it created a black market for them? Two people during the trial who,
unbeknownst to anyone, were actually developing an HIV infection when they
started PrEP, appear to have developed drug-resistant HIV as a result. What if
PrEP sows the seeds of resistance in the population, as substandard treatment
did in the 1990s?
“We, as a community of advocates, must now confront
difficult questions about roll-out, cost, HIV prevention messaging and the
place PrEP takes,” was the message from the Global Forum on Men Who Have Sex
with Men and HIV (MSMGF). The Forum pointed out that there was no chance of
PrEP working in many parts of the world if it required that men self-identify
as gay where doing so risks violence or imprisonment.
Other advocates, however, welcomed PrEP as another piece of
evidence to support the contention that the only way to defeat HIV is to treat