Research

What is donanemab?

Recently we have heard that a drug called lecanemab that slows down memory and thinking decline has been approved to treat early Alzheimer’s disease by the Medicines and Healthcare products Regulatory Agency (MHRA). The UK is  amongst other countries that have approved lecanemab, including US, Japan and China. However draft guidance from the National Institute for Clinical Excellence does not recommend it for use on the NHS at this stage.

Donanemab works in a similar way to lecanemab and we are waiting to hear if the MHRA will approve it as the second drug available for people with early Alzheimer’s disease. 

What is donanemab?

Donanemab is a disease-modifying drug. This means that it was developed to tackle the causes of Alzheimer’s disease rather than only relieving the symptoms.

Donanemab was developed by a pharmaceutical company called Eli Lilly. It targets a protein called amyloid. The importance of this protein in the development of Alzheimer’s disease was discovered by Alzheimer’s Society funded research led by Professor Sir John Hardy over thirty years ago. It laid the foundations for billions of pounds of investment into many drugs like donanemab, with 127 other drugs currently being tested in clinical trials. 

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.

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. 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.

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).

From the start of 2024 the UK government changed the process for MHRA to approve of new drugs. The new system will allow ‘rapid, often near-automatic sign-off for medicines and technologies already approved by trusted regulators in other parts of the world such as the United States, Europe and Japan’. 

Donanemab has recently been approved for use by the US regulator. This may mean that we also hear a decision from the MHRA about donanemab later in 2024.

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.

A similar drug, lecanemab was approved for use in the UK by the MHRA. But was not recommended by NICE to be made available on the NHS.

We don’t know if the MHRA and NICE will make the same decisions about donanemab as they have done with lecanemab. Differences in how safe and effective the drug is, as well as its cost-effectiveness mean that the decision will be independent of the decision about lecanemab.

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.

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 build-up 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.

How can you get involved in dementia research?

Alzheimer’s Society is a partner in a service called Join Dementia Research (JDR). The service allows anyone over the age of 18 to register their interest in participating in dementia research; however, researchers are particularly keen to hear from those with a diagnosis of dementia/ or MCI and those that care/support them to register.

If you would like to hear more about this service then please contact our Join Dementia Research helpdesk by calling 0333 150 3456 and asking for the Join Dementia Research helpdesk or emailing us directly at: [email protected].

We will update this page as new information becomes available. Last updated: 22 August 2024.