The media do love to run reports about wonder drugs. The latest is aducanumab, which is being widely reported as a breakthrough in the treatment of Alzheimer’s disease. The Telegraph hails a ‘new drug that halts mental decline’. The Mail headline asks: Could this be the end of Alzheimer’s? Revolutionary drug ‘may stop the disease from ever developing.’ For those with access, the actual report of the trial is in Nature.
There are several reasons why this is over-hyped, and it’s not just that this is based on a small sample from first stage trials.
- Dementia is not a disease, but a syndrome; the symptoms of dementia are known to be the result of a variety of different pathologies.
- It’s far from clear that Alzheimer’s is a single disease with a common cause. It’s widely used as a residual category for dementias that have not been explained in other ways.
- It’s not clear how far the amyloid-β proteins that the drug is removing are actually responsible for dementia. It’s a plausible hypothesis; but, as point 2 implies we should expect, there are some apparent cases of Alzheimer’s without amyloid-β plaques, and because the proteins (Aβ and tau) can build up for 15-20 years without symptoms emerging, the presence of the proteins does not mean that the person with a build up will suffer dementia.
- It’s not clear that whether, if the hypothesis is correct, the plaques impair cognition which might be relieved, or cause permanent damage. This study claims, with few direct details, that cognitive decline is slowed – but the comparison they make is not between drug receipt and placebo, but between those cases who had both received the drug and recovered better from plaques from those who received the drug without that effect.
Lastly, it ought to be noted that many people dropped out of the trial, at least 20 because of side effects. The way that drug trials work – or should work – is that the tests should be able to refine the identification of those for whom the drug is appropriate, and those for whom it isn’t. That takes time and good science, and hype and the search for miracle cures tends to get in the way of that.
Additional note, 5th November 2019: The i newspaper carries the page 1 headline:
The woman who defied Alzheimer’s: Patient with rare genetic mutation raises fresh hope that a cure for dementia can be found.
I started to cover this on the blog, but this earlier post already says what needed to be said. All together, now: there is no cure for dementia. The much-maligned NHS website says it plainly:
There is currently no “cure” for dementia. In fact, because dementia is caused by different diseases it is unlikely that there will be a single cure for dementia.
Further additional note, 6th November 2021:
New Scientist has finally caught up with the argument.
“Alzheimer’s, as currently understood, is really not a single disease. … This new approach comes not a moment too soon … Tunnel vision has held us back for too long. With this new approach, a single blockbuster drug might well be out of the picture, but instead, there is a real possibility that we could dismantle Alzheimer’s by a thousand cuts.”