What is donanemab? The drug that has raised hopes

How does it work?

Donanemab is made by the US pharmaceutical firm Eli Lilly and Company and is a monoclonal antibody that targets amyloid in the brain.

Amyloid is a protein made by brain cells. People with Alzheimer’s develop plaques as the amyloid clumps together. The protein is thought to be toxic to the brain and can cause cells to die as it stops them communicating, leading to cognitive decline, dementia and Alzheimer’s.

The new drug inserts antibodies into the person’s system that attack the amyloid plaques and break them down. This helps slow down progression. The drug specifically targets one amyloid protein called N3PG. This is found extensively in the brain plaques of Alzheimer’s patients but scarcely elsewhere in the body, allowing for more accurate treatment.

How effective is it?

Early trials show dononemab slows cognitive decline by about 35 per cent.

Almost half (47 per cent) of people in the study who took the new drug had no decline from their initial condition and experienced a 39 per cent lower risk of progressing to the next stage of the disease compared with placebo. How soon can NHS patients get it? The drug has been in trials for a decade already. Pre-clinical trial data of dononemab (then called just LY3002813) tested on mice was presented at AAIC 2014 in Copenhagen. Clinical trials will continue on the Eli Lilly Alzheimer’s drug while global regulatory approval is sought.

The UK’S Medicines and Healthcare products Regulatory Agency (MHRA) will now determine whether to give dononemab approval if the data show it to be safe and effective.

The National Institute for Health and Care Excellence (Nice) must also recommend whether it is made available based on cost-effectiveness, benefit to life, and expert opinion. A timeline on these processes is far from concrete, and MHRA approval alone can take several months, even if expedited, as in this instance.

Lecanemab received Federal Drug Aministration (FDA) approval in the US in January. Eli Lilly said it “will proceed with global regulatory submissions as quickly as possible”. Are there any side-effects?

Yes, the study found an increased prevalence in some brain swelling and bleeding conditions among people taking the drug.

Amyloid-related imaging abnormalities (Aria) were detected by MRI and brain swelling was seen in a quarter of participants. Brain microhemorrhages or superficial siderosis, known as Aria-h, occurred in almost one in three patients.

Eli Lilly claims most Aria cases were mild or moderate and it is usually an asymptomatic condition. But two people in the study died of Aria and a third died after an incident of serious Aria.