Donanemab was approved by the Medicines and Healthcare products Regulatory Agency (MHRA) for use in adults in the early stages of Alzheimer’s disease in Great Britain in October 23, 2024. Donanemab has been shown to slow the progression of Alzheimer’s disease in individuals with one or no copies of the apolipoprotein E4 gene.

Alzheimer’s disease is characterised by the abnormal accumulation of extracellular plaque deposits of amyloid beta, and tau neurofibrillary tangles, thought to contribute to the cognitive decline seen in the disease.

Similarly to Lecanemab, the first treatment licensed for Alzheimer’s disease in Great Britain in August 2024, Donanemab is a monoclonal antibody which is thought to slow the progression of Alzheimer’s disease through its ability to reduce the size of amyloid beta plaques in the brain.

Donanemab was evaluated in 1,736 patients with early Alzheimer’s disease who had evidence of amyloid pathology as well as mild cognitive impairment or mild dementia. Donanemab was administered intravenously every 4 weeks for up to 72 weeks. The treatment significantly reduced amyloid plaques compared to placebo. However, this effect was driven by individuals with no or one copy of the apolipoprotein gene. Individuals with two copies of this gene did not benefit from the treatment, and were more likely to experience side effects, including swelling and bleeding in the brain.

Since amyloid beta proteins accumulate in the walls of small blood vessels, both Lecanemab and Donanemab have been associated with side effects, including brain swelling and bleeding in the brain. Whilst these side effects can be closely monitored using magnetic resonance imaging (MRI) scans, this is very costly.

Given the high costs associated with purchasing both Donanemab and Lecanemab, and high costs associated with administering and monitoring the side effects of the drug, NICE did not recommend their use on the NHS since the small benefits to patients did not justify the high cost to the UK taxpayer.