Is Alzheimer’s drug donanemab really a ‘turning point’ for treatment?
The experimental drug donanemab slows the progression of Alzheimer’s disease compared with a placebo, but the effect may not be large enough to be noticed by people with the condition or their families
By Clare Wilson
18 July 2023
PET scans are required to detect amyloid levels in the brain before donanemab can be administered to treat Alzheimer’s disease
Eli Lilly
The full clinical trial results for an Alzheimer’s therapy called donanemab were released on Monday. While the experimental drug has been hailed as a turning point in treating the condition, questions remain about its effectiveness, safety and practicality.
What is donanemab and how does it work?
Donanemab is an antibody that binds to a protein in the brain called amyloid, which is thought to play a role in Alzheimer’s disease.
Results from a large trial of more than 1700 people found that after 18 months, those who received the treatment had less progression of their dementia symptoms, such as memory loss and confusion, than those who got a placebo. The symptom scores for those who got the treatment were about 30 per cent lower than the people in the placebo group, overall.
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What does this mean for people with Alzheimer’s?
The result might sound like good news, but some doctors are urging caution, including in an opinion piece in the journal JAMA that accompanied the results. Concerns mainly centre on the relatively small benefit from the drugs, potentially fatal side effects and practical difficulties in health systems’ capacity to give brain scans – which are necessary before the treatment can begin – to everyone who might benefit.
Is any improvement welcome when it comes to Alzheimer’s?
People who got the drug didn’t improve, they deteriorated at a slightly slower rate than those who had a placebo. Doctors have also questioned whether the degree of slowed deterioration would be noticed by people with Alzheimer’s or their families.
An analysis published in 2019 in collaboration with donanemab’s manufacturer, Eli Lilly, concluded that, for a noticeable effect, a treatment would need to produce at least a 1-point difference on a symptom rating scale. In the latest trial, the 30 per cent figure came from a 0.7-point difference between the donanemab and placebo groups. Eli Lilly, however, has previously said that the 2019 analysis concerned differences between individuals, not the averaged effects on groups of people.
