Q&A: Alzheimer’s trial results offer hope for sufferers and their families

The release of trial results into a new treatment for Alzheimer’s disease has created a worldwide buzz. Why are people excited?

Until now, approved drugs have only been able to treat the symptoms of Alzheimer’s disease, for example by delaying memory loss by a few months. They do not treat the root cause of the disease and so do not slow down the pace of deterioration. However, final trial results of a new type of drug, donanemab, presented to the Alzheimer’s Association International Conference in Amsterdam on Monday, concluded that after 76 weeks of treatment it had slowed clinical decline by 35 per cent in people with early Alzheimer’s.

How does the new treatment work?

Donanemab, and another drug lecanemab, are immunotherapy drugs. They work by teaching the body’s immune system to recognise and remove a protein called amyloid, which builds up in Alzheimer’s disease. Some researchers believe this build-up is the root cause of Alzheimer’s.

The brain is made up of billions of nerve cells that connect to each other. In Alzheimer’s disease, connections between these cells are lost. This is thought to be because the build-up of amyloid creates abnormal structures called “plaques” and “tangles”.

How is donanemab different from lecanemab, the other drug touted as an Alzheimer’s treatment?

Donanemab and lecanemab are both immunotherapies and are given intravenously. 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 make plaques or tangles.

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These drugs are unlikely to 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.

However for those with early Alzheimer’s, after one year taking donanemab, nearly half of the people taking it had no decline in memory and thinking skills. They also had a 40 per cent reduction in the decline of their ability to carry out daily activities, such as managing finance, driving and following hobbies.

Both drugs have similar side effects, including a small risk of brain swelling.

When could we expect to see these drugs approved for use?

An application for approval for lecanemab has already been submitted to the European Medicines Agency, while an application for donemebab is imminent. A decision on both drugs is expected in 2024.