The PReP roller-coaster: no good for women?

Just as we were getting all excited about giving people antiretorvirals to protect them against HIV infection, a large trial of pre-exposure prophylaxis (PReP) in women is being shut down because the pills are unlikely to prevent HIV.

It’s a huge disappointment to those who were hoping that the pill-a-day-to-avoid-a-pill-a-day solution might drag us out of the despond that we’ve been in as we contemplate 2.7 million new HIV infections this year. That’s the same number as were newly infected when I started in this business 15 years ago. The only real change is in the cost of our failure: that’s increase over 70-fold.

The study, well conducted by my former employers Family Health International in four countries, is at odds with a study released last November, that showed that a daily dose of Truvada, a combination of two antiretorvirals in pill form, cut the risk of infection among gay men by over 40%. The earlier study did show that — surprise surprise — taking pills to prevent HIV doesn’t work unless you actually take your pills. Though virtually everyone said they took their pills, a later analysis of blood samples showed that wasn’t true. We don’t yet have that same analysis for the new trial in women (dubbed FemPrep), so although 95% reported taking their pills, it’s possible that real adherence was much lower. More than possible: likely. All women in the study were taking contraception, but there was a 9% pregnancy rate, apparently much higher in women on the pill than women on injectibles (we don’t yet have the actual numbers). That suggests that some women aren’t all that good at taking one pill a day (I’m one of them; thank God for implants), let alone two.

There’s a real possibility that antiretrovirals taken through the mouth and processed through the digestive tract aren’t as effective at preventing HIV from finding an entry point in the vagina as they are in the rectum, hence the difference between the trials in straight women and gay men. If that’s the case, it ups the ante for putting ARVs directly into your fanny (using fanny in the English sense!). We know from the Caprissa trials that antiretroviral microbicide works vaginally (though not necessarily rectally). But we only know that it works if you “shoot up” both before and after sex; in theory, at least, that is what was being tried. In practice, we know (well, strongly suspect) how unlikely it is that women will actually do that on a long-term basis. We now desperately need trials of a one-shot vaginal microbicide. Because for all the talk of “bio-medical solutions” the confusing results of recent HIV prevention trials remind us that most bio-medical solutions have a very strong behavioural component. Pills that “work” if you take them are no good if they make you feel so sick, so choked, or so fed up that you don’t take them.

One of the things that pleased me greatly about the FemPrep trials was that researchers made sure that the women who volunteered for the research knew about the disappointing results before the press or the scientific community did. There are more details from the study teams about how they interacted with participants on this interesting conference call, arranged by the ever-helpful AVAC network.

This post must end the way these posts seem always to end, with an underlining of the shockingly high rate of new infections in the study overall: five percent of women became infected, despite the fact that they were given female and male condoms, were regularly screened for other sexually transmitted infections and treated as necessary, and counseled up the wazoo. It’s a reminder of how badly suited the tools in our current toolbox are to the job of HIV prevention, and a caution about expecting much more from other behavioural interventions such as the use of pills or gels.

This post was published on 22/04/11 in Science.

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  1. Comment by Milly Katana, 05/05/11, 06:45:

    Always well put, Elizabeth!

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