Lecanemab and Donanemab: the UK position

What Lecanemab and Donanemab are

Lecanemab (brand name Leqembi) and Donanemab (brand name Kisunla) are monoclonal antibodies that bind to amyloid-beta in the brain and trigger its removal. They are the first medicines that target the underlying biology of Alzheimer's Disease rather than only its symptoms. Both are licensed by the United States Food and Drug Administration; Lecanemab has received marketing authorisation in the European Union and Great Britain, and Donanemab's regulatory pathway in Great Britain is in progress.

Who the medicines are designed for

Both medicines are studied in early Alzheimer's Disease, defined as Mild Cognitive Impairment due to Alzheimer's Disease (positive amyloid biomarker) or Mild Alzheimer's Disease Dementia. They are not designed for moderate or severe disease, for Vascular Dementia, for Dementia with Lewy Bodies, or for Frontotemporal Dementia. People with significant Cerebrovascular Disease, certain genetic variants (APOE4 homozygotes have higher risk), recent strokes, or who are taking anticoagulants are at increased risk of side effects.

What the trial evidence shows

Lecanemab (CLARITY-AD)

The pivotal CLARITY-AD trial enrolled 1,795 people with early Alzheimer's Disease and randomised them to Lecanemab or placebo for 18 months. Lecanemab slowed cognitive and functional decline by approximately 27 per cent on the Clinical Dementia Rating Sum of Boxes scale and similarly on other measures. Brain amyloid was substantially reduced.

Donanemab (TRAILBLAZER-ALZ 2)

The pivotal TRAILBLAZER-ALZ 2 trial enrolled 1,736 people with early Alzheimer's Disease. Donanemab slowed cognitive and functional decline by 22 to 35 per cent, depending on the subgroup analysed (greater effect in lower-tau participants). Brain amyloid was cleared in many participants, allowing dose tapering or discontinuation.

The risks: Amyloid-Related Imaging Abnormalities (ARIA)

The main safety concern with both medicines is Amyloid-Related Imaging Abnormalities, or ARIA, seen on Magnetic Resonance Imaging. Two forms occur:

• ARIA-E (oedema, fluid-related signal change), which is usually asymptomatic but can occasionally cause headache, confusion, seizures, or focal neurological signs;
• ARIA-H (haemorrhage, small bleeds or microbleeds), again usually asymptomatic but rarely associated with larger bleeds.

ARIA occurs in around 20 to 30 per cent of people treated, more often in APOE4 homozygotes. Most events are mild and resolve without consequence; serious or fatal events have been reported in a small minority. Regular Magnetic Resonance Imaging monitoring is required throughout treatment.

The UK NICE position

In June 2025 NICE published draft guidance on both medicines:

• GID-TA11220 (Lecanemab): recommended against routine NHS use or managed access.
• GID-TA11221 (Donanemab): recommended against routine NHS use or managed access.

The reasons cited include the modest clinical benefit relative to the substantial cost of the medicine itself, the substantial infrastructure costs of delivering intravenous infusions and Magnetic Resonance Imaging monitoring, and uncertainty about the long-term balance of benefits and harms. The decision was a close one and may be revisited.

Could I access these medicines privately?

Private access in the United Kingdom is theoretically possible but has not been at scale. Costs are high (the medicine alone is typically £20,000 to £35,000 per year, plus infusion and monitoring costs). Some specialist centres and private memory clinics are exploring delivery models. Stability of supply, infrastructure for intravenous infusion, ARIA monitoring, and informed consent are all material considerations.

For most people in the UK at present, the focus remains the established treatments: Cholinesterase Inhibitors, Memantine, aggressive vascular risk reduction, and non-pharmacological supports.

How the position may change

Several developments could change the UK position in the next few years:

• Long-term follow-up data clarifying durability of benefit;
• Identification of subgroups (such as APOE non-carriers, lower-tau cases) who derive most benefit and least risk;
• Lower-cost biosimilar or next-generation antibodies;
• Subcutaneous formulations reducing infrastructure cost;
• Additional indications and combination strategies.

NICE has indicated that it will revisit the appraisals if such evidence emerges. We will update this page when the position changes.

Where to discuss the options

If you would value an independent clinical opinion on whether anti-amyloid antibody therapy is right for your situation, The Dementia Service can review the diagnosis, the current evidence, and pathways for clinical trial enrolment and private access where these are appropriate.