Scientists have questioned a “breakthrough” Alzheimer’s drug after more details of its side effects have been released.
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Final clinical trial results for lecanemab show that the drug was able to slow the rate of decline in people’s memory and thinking as well as function over 18 months, and also helped people with day-to-day activities.
Dementia experts hailed a potential “historic moment” when some of the final results were published in September, but questions remained over lecanemab’s side effects.
The full results, published at the Clinical Trials on Alzheimer’s Disease conference in San Francisco confirm a “robust effect” of slowing of cognitive decline of 27 per cent compared to those people in the study who were not given the drug.
The trial, known as Clarity AD included 1,795 people with early-stage Alzheimer’s and mild cognitive impairment (MCI) due to Alzheimer’s, who received a bi-weekly infusion of either lecanemab or a placebo.
The paper, published in the New England Journal of Medicine, gave more details of a prominent side effect of lecanemab known as amyloid-related imaging abnormality (Aria), which involves a bleed or build up of fluid in the brain. It can vary from mild and negligible to quite severe.
Some 12.6 per cent (or 1 in 8) of those who received lecanemab developed Aria, while 1.7 per cent (less than 1 in 50) developed it in the placebo group. Although there were a similar number of deaths in both groups eight in the lecanemab group and seven in the placebo group scientists said further follow up is needed to understand whether Aria in certain patients is life threatening.
If so, it may be that patients receiving such treatments need to be excluded. Further studies will be able to identify the patients at risk and those patients who will maximally profit from the treatment.
The paper also suggests further studies to evaluate how effective and safe lecanemab is are ongoing, as a key question is whether clinical benefits are progressive in that they continue beyond the 18 months, and whether they are sustained.
Rob Howard, professor of old age psychiatry at UCL, asked whether the drug was safe. He said: “Recent reports of two deaths from strokes, attributed to a side-effect of the drug, are concerning. The data indicates that six lecanemab-treated patients suffered strokes during the trial compared with two in the placebo group. Treatment therefore does carry risks, and in some rare cases this can be severe or life-threatening.
“I suspect that the lack of demonstrable clinical effectiveness will mean that lecanemab will not be taken up widely within healthcare systems around the world, although there will always be those whose heart rules their head. We need to keep looking for better and safer dementia treatments and today’s results show that we are now on a believable path to doing so.” ■
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