Developments in dementia treatments

Dementia is not a single disease; it is a general term used to describe the progressive deterioration of cognitive functioning ("thinking, remembering and reasoning"). Alzheimer’s disease is the most common type of dementia, accounting for between 60% and 70% of all dementia cases. It is thought to be caused by the build-up of two types of proteins, tau and amyloid, in and around brain cells.

There is currently no cure for dementia. There are medicines and treatments that can help manage, or temporarily reduce, some of the symptoms. However, these do not treat the cause of the underlying disease and therefore do not stop its progression.

Disease-modifying treatments

There are some new ‘disease-modifying’ treatments in development that are aimed at people in the early stages of dementia, who have a mild cognitive impairment / mild dementia, due to Alzheimer’s disease. These are drugs that slow (but do not stop) the progression of dementia.

This briefing focuses on two disease-modifying dementia drugs that are currently being appraised by the National Institute for Health and Care Excellence (NICE): lecanemab and donanemab.

The drugs, known as immunotherapies, aim to slow the progression of the disease by helping the immune system to recognise, target and break down the amyloid plaques (clusters of proteins) in the brain. Lecanemab does this by "targeting 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".

Neither drug is a cure for Alzheimer’s disease. However, a clinical trial of lecanemab reported that it slowed the rate of cognitive decline by 27% in those with early Alzheimer’s disease, compared to the placebo group. A clinical trial of donanemab reported that it slowed the progression of Alzheimer’s disease by 36% when compared to the placebo group, again in those with early Alzheimer’s disease.

As with all drug treatments, both lecanemab and donanemab have side effects; in most instances the clinical trials found that these were ‘mild to moderate’ (such as fever or headaches). However, there is a potentially more serious adverse event, associated with both lecanemab and donanemab, known as ‘amyloid-related imaging abnormalities’ (ARIA). These present as either fluid or bleeding on the brain. While ARIA was typically asymptomatic, and resolved on its own within a few months, there were three fatal cases of ARIA in the donanemab trial. The researchers reported that their deaths were "considered treatment related". Both studies emphasised that further, longer-term trials are needed to understand, and evaluate, the risks of ARIA, as well as how best to manage them.

Preparing for new treatments

In the UK, lecanemab has been approved (licenced) by the Medicines and Healthcare products Regulatory Agency (MHRA – the UK’s medicines regulator) to treat adults in the early stages of Alzheimer’s disease. Draft guidance on lecanemab, issued by NICE in August 2024, did not, however, recommend lecanemab for use on the NHS. This was on the grounds that its benefits were "too small to justify the costs".

Donanemab was approved for use in the UK by the MHRA in October 2024. As with lecanemab, draft guidance issued by NICE has not recommended donanemab for use on the NHS in England: NICE said that its cost-effectiveness estimate "is 5 to 6 times above what [it] normally considers an acceptable use of NHS resources".

Final draft guidance on lecanemab and donanemab was published by NICE in June 2025. It confirmed that the benefits of both treatments “remain too small to justify the additional cost to the NHS”. Registered stakeholders, including the companies responsible for the drugs and patient groups, had until 3 July 2025 to appeal against the final draft recommendations.

NHS England has described implementing these new treatments, should they be approved by the MHRA and recommended by NICE, as "one of the biggest challenges the NHS has faced in its 75-year history". This is partly because the effectiveness of the treatments depends on both an early diagnosis of dementia, and a further diagnosis of the sub-type, to confirm the treatment is suitable. Diagnosing subtypes of dementia requires more advanced and invasive procedures which, stakeholders say, are not widely available in the NHS. Alongside diagnostic capacity issues in the NHS, psychiatrists have expressed concern about having sufficient staffing, skills and resources to deliver and monitor new treatments.

Dementia policy

A 10-year plan to tackle dementia had been expected in 2022. In January 2023, the Conservative government announced it would instead publish a Major Conditions Strategy (MCS) covering six conditions, including dementia. The Labour government has since paused work on the MCS, later adding that it would consider how best to meet the needs of people with dementia as part of its work to develop a 10-year plan to reform the NHS. The 10-year health plan for England was published in July 2025 and was informed by the conclusions of Lord Darzi’s Independent investigation of the NHS in England. The development of a ‘modern service framework’ for frailty and dementia is promised in the plan. This would set “clearer standards for how tests and treatments are provided” and encourage “local NHS services to improve and coordinate better”.