Donanemab is currently in the headlines as a drug that appears to slow down memory and thinking decline in people living with early-stage Alzheimer’s disease. Here's what we know so far about this Alzheimer's drug.
In the last year, we have heard of two new drugs, lecanemab and donanemab, which can slow down the decline in memory and thinking skills of people living with early Alzheimer’s disease.
Does donanemab work?
Donanemab is a disease-modifying treatment. This means that rather than only relieving the symptoms of Alzheimer’s disease, it tackles one of the root causes.
New results released in July 2023 showed that donanemab works better the earlier it is given.
Donanemab slowed how fast memory and thinking get worse by more than 20%. The evidence from the trial suggests that the earlier in the disease the treatment was given, the greater the benefit. This means that there was more slowing in memory and thinking decline in people with fewer changes in their brains associated with Alzheimer’s disease.
This means a delay in the progression of Alzheimer’s disease by 4.5-7.5 months over the 18 months of the trial.
Also after one year on donanemab, nearly half of the people taking it had no decline in memory and thinking skills.
People taking donanemab also had a 40% reduction in the decline of their ability to carry out daily activities, such as managing finance, driving and carrying out hobbies.
These are exciting results, but we don’t fully know what this will mean in the long term for people who have taken donanemab as the trial only lasted 18 months.
Also, 91.5% of the participants in the trial were from a white background, so we need more diversity in clinical trials to prove that these drug treatments will work for everyone with early Alzheimer’s disease.
Is donanemab safe?
As well as testing the effectiveness of donanemab, the clinical trial also tested the safety of the drug, with monitoring for bad side effects.
As with all drug treatments, there have been some side effects associated with donanemab.
These included headaches, reactions to the intravenous drip, and swelling or microbleeds in the brain known to be related to amyloid.
The vast majority of side effects (82.4%) were either mild or were detected in tests but didn’t cause any symptoms
Unfortunately, there were three deaths (0.4% of participants) in the trial related to brain swelling and 1.6% of participants had serious symptoms relating to brain swelling.
Safety will be carefully considered alongside the benefits of the drug by regulatory authorities.
They will decide whether the drug should be made available to people with early stage Alzheimer’s disease.
How does donanemab work?
Donanemab is given to patients intravenously, which means into a vein through a drip bag. It is an immunotherapy drug developed by a pharmaceutical company called Eli Lilly. Immunotherapy drugs are already used in medicine for treating different diseases, like cancers.
They tell the body’s immune system to attack foreign cells or proteins and get rid of them so they can’t cause any more problems. In the case of donanemab, it teaches the immune cells to recognise and remove a protein called amyloid, which builds up in Alzheimer’s disease.
The amyloid protein build-ups are thought to be toxic to brain cells, causing them to get sick and eventually die, leading to the symptoms of Alzheimer’s disease.
Three-quarters of the people taking donanemab had amyloid successfully cleared from their brains by the end of the trial.
How is donanemab different from lecanemab?
Donanemab and lecanemab are both immunotherapies. Although both drugs target amyloid protein, they target it at different stages in how it builds up in the brain.
Lecanemab targets amyloid as it begins to form fibres, whereas donanemab binds to amyloid once these fibres have clumped together to become a larger build-up or plaque in the brain.
This may be partly why we see a difference in how effective both drugs are at slowing down the disease.
Who would be eligible to take donanemab?
To be eligible for donanemab treatment a person would need to be in the early stages of Alzheimer’s disease and have amyloid protein buildup present in their brain. This is shown using amyloid PET scans or testing of spinal fluid.
Trials have tested donanemab in people with early stage Alzheimer’s disease.
Researchers believe these types of drugs may not be effective for people with moderate or severe Alzheimer’s disease, as the amyloid protein will have already caused too much damage to the brain for the drug to help.
If it is approved in the UK, donanemab is likely to only be available for people living with early stage Alzheimer’s disease.
When might donanemab be available in the UK?
To be available for use in the UK, a drug needs to be approved for use by the Medical and Healthcare Products Regulatory Agency (MHRA) But this only allows it to be legally used in the UK.
For it to be available on the NHS it will then also need to be reviewed by the National Institute of Health and Care Excellence (NICE).
They will consider the cost-effectiveness of donanemab, as well as the benefits and side effects.
This means that if decisions are positive, the very earliest donanemab might be available on the NHS is 2025.
This article was first published 3 May 2023 and most recently updated on 17 July 2023.
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