Donanemab – what we know about the latest Alzheimer’s drug

But what is the drug and how does it work? Here your questions on the latest development in Alzheimer’s research are answered.

– What kind of treatment is Donanemab?

Donanemab is a targeted antibody drug which slows down the early stages of Alzheimer’s.

The drug, and another new drug for Alzheimer’s called lecanemab, have been billed as a huge step forward in research because they target a known cause of the disease, rather than just treating the symptoms.

Both drugs bind to amyloid, a protein which builds up in the brains of people living with Alzheimer’s disease.

By binding to amyloid, the drugs are designed to help clear the build-up and slow down cognitive decline.

– How effective is it?

Manufacturer Eli Lilly found that the drug “significantly” slowed cognitive decline in Alzheimer’s patients in its clinical trials.

Donanemab, also known as Kisunla, was found to slow the rate at which memory and thinking get worse by more than 20%.

Results also suggest the drug leads to a 40% reduction in the decline of everyday activities such as driving, enjoying hobbies and managing money.

Evidence suggests that people get the most benefit if they are given the treatment earlier in the disease.

Treatment with donanemab reduced amyloid plaque on average by 84% at 18 months, Lilly found.

– How are the drugs given?

Donanemab is given to patients via an intravenous drip once every four weeks.

Lilly has said that some patients can complete their course of treatment in as little as six months once their amyloid plaque has cleared.

During the clinical trial patients were able to stop taking donanemab once they had cleared a certain amount of amyloid plaque. Around half of those involved in the trial met this threshold a year into treatment.

– Are there any side effects?

Side-effects of the donanemab, and other similar drugs, can be serious.

Donanemab has been linked to “amyloid-related imaging abnormalities (Aria)” which does not usually cause symptoms but can be picked up on brain scans.

These can include temporary brain swelling or micro brain bleeds – these can be serious and even fatal in some cases.

In one clinical trial published in the Journal of the American Medical Association in 2023, 24% of people receiving donanemab had Aria.

Lilly recommends that the risk should be managed “with careful observation, monitoring with MRIs, and appropriate actions if Aria is detected”.

Three deaths were reported among the people receiving donanemab during the trial which were considered “treatment related”, according to the 2023 paper. One treatment-related death was reported in the group who receive the placebo – also known as a dummy drug.

The majority of side effects (82.4%) were either mild or were detected in tests but did not cause any symptoms.

– How does a drug get approved for NHS use in the UK?

For a drug to be used in healthcare in the UK it needs to be given approval by the Medicines and Healthcare products Regulatory Agency (MHRA). The MHRA will assess the safety and efficacy of the drug before making a decision.

Before the new treatment is approved for widespread use in the health service it needs a green light from the National Institute for Health and Care Excellence (Nice) – the NHS’ spending watchdog.

The US Food and Drug Administration (FDA) approved Kisunla for the treatment of Alzheimer’s disease in July.

– What happened with lecanemab?

The MHRA approved lecanemab but it was swiftly rejected by Nice.

Nice said the benefits of lecanemab are “just too small to justify the significant cost to the NHS”.

Lecanemab is already licensed in the US, where it costs about £20,000 per patient per year.

The European Medicines Agency (EMA) rejected lecanemab in late July.

It said that the drug’s effect on delaying cognitive decline “does not counterbalance the risk of serious adverse events associated with the medicine”.

But in August the regulator said that it will re-examine its opinion before issuing a final recommendation.

– How much do the drugs cost?

Each vial of Kisunla is 695.65 dollars, according to Lilly documents.

The overall cost of donanemab for each person will depend on how long they are on it.

NHS England has published a briefing paper suggesting the cost of bringing new Alzheimer’s disease modifying treatments to the health service could be £500 million to £1 billion per year.

Around 50%-60% of the total estimated cost relates to the drug cost, with remaining cash spent on patient assessment, diagnosis and administering the treatment.

– How do I know if I am eligible?

NHS England estimates between 50,000 and 280,000 patients might be eligible for the new treatments if they are approved for the NHS.

If the drugs are approved, patients will need to have a baseline MRI scan and then either a PET-CT scan or lumbar puncture to confirm Alzheimer’s.

It is possible that blood tests will be available in the future to diagnose the disease, so NHS England has said there should be caution about driving a “massive expansion” in other diagnostics which could become redundant in the longer term.

– What have experts said?

When the stage 3 clinical trial results were reported in 2023, some experts said that the findings were “incredibly encouraging”.

Others have been cautious – with particular concerns raised about the potential side effects of the treatment.