27/10/08

Sooner is better for HIV treatment (and Pharma)

A CD4 Molecule

A CD4 Molecule

A new study suggests that people with HIV have a 70% greater chance of staying alive if they start taking antiretrovirals when their CD4 count is as high as 500. That’s good news for people who know they are infected early on and who have easy access to drugs. It’s also potentially good news for the people who make the drugs, bumping up their market size quite substantially.

CD4 molecules are attached to T-cells that defend the body against infection. CD4-bearing T-cells get knocked out by HIV infection; so the number per microlitre of blood is used to track the progress of HIV as it cuts its destructive swathe through the body. The US currently recommends starting antiretroviral treatment when the CD4 count hits a low of 350. The new study, which pools data from a large number of north American patients, suggests that a significant number of people die before they hit 350. The study’s author Mari Kitahata was involved in developing the existing guidelines, but in view of the new data she suggests people should start taking drugs when their CD4 count hits 500. Kitahata, a highly respected researcher at the University of Washington who provides advice to several pharmaceutical firms, is now investigating whether there’s anything to be gained from taking drugs even earlier in the course of infection.

This news will cause consternation in a lot of developing countries, where current guidelines recommend starting people on meds at a CD4 of 200 — a level which more or less goes hand in hand with symptomatic AIDS. Raising the threshold to 350 would mean hundreds of thousands more people would need to be put on meds. A threshold of 500 would mean millions more people needing uninterrupted access to expensive drugs. This would cost a fortune; at the risk of sounding callous, I think we would be very well advised to make careful estimates of exactly how many additional lives would be saved. Obviously, doctors treating people with HIV want to keep their patients alive. To them, and of course to the patients, a 70% decrease in the chance of dying is pretty persuasive. But in real terms, not all that many people are dying in the US cohorts (3 per 100 person years among those who took drugs earlier, against 3.2 per 100 person years among those who took drugs later). Kitahata and her colleague Daniel Kuritzkes were abit vague about the costs and benefits of getting people started on drugs earlier; check out the transcript of a press conference discussing the study results over at The Body. (The transcript also contains newer data than the published abstract.)

One thing that wasn’t discussed at the presser was the potential downside of being on antiretrovirals for longer than is necessary. I’d be curious to know more about the long-term effects of taking antiretrovirals, how many extra years of drug-taking a higher threshold would imply, and whether, at a population level, the extra years of drug-taking would mean a lot more discomfort and sickness related more to the drugs than the virus. It’s a very difficult thing to look at, not least because drug regimes have improved so much over time. But I’d welcome information from anyone who has looked at these issues.

If we are going to try to provide drugs earlier, it’s one more reason to push for more routine HIV testing among the people most likely to have been exposed to the virus. Even in the highest risk groups — in the US and the UK that would be gay men — between a fifth and a quarter never learn of their HIV infection until an AIDS-related condition lands them in hospital or at the doctor’s clinic. That’s usually way after the CD4 count has crashed through 500 and even 350. Earlier treatment depends on earlier diagnosis. In countries which might just put people on treatment earlier, these data might just persuade more people to find out if they’re infected.

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This post was published on 27/10/08 in Science.

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