Lecanemab (Leqembi) for early-stage Alzheimer's disease

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Lecanemab (Leqembi) for early-stage Alzheimer's disease

Lecanemab (Leqembi) for mild cognitive impairment

At the end of 2025, the German Institute for Quality and Efficiency in Health Care (IQWiG) assessed whether lecanemab has advantages or disadvantages compared with active surveillance (a "watch-and-wait" approach) in adults with mild cognitive impairment (MCI) who meet the other necessary criteria to be able to have treatment with lecanemab.

The manufacturer provided one study involving just under 1,800 participants. For the assessment, researchers at IQWiG analyzed the data of a relevant subgroup of almost 500 people in this study. The people in this subgroup met all of the necessary criteria to be able to have treatment with lecanemab:

  • They had a mild cognitive impairment (memory and thinking problems).
  • Certain protein deposits (amyloid plaques) typical of Alzheimer's disease had been found in their brain.
  • They had only one copy, or no copies, of a specific version of a gene (ApoE4).
  • They were not taking anticoagulants ("blood thinners") at the start of the study.

252 of the people in the subgroup received lecanemab, and 245 of them were given a placebo (a "fake" medication). All of them received the usual medical care. Study participants who had been given cholinesterase inhibitors (donezepil, galantamine, rivastigmine) or memantine were not included in IQWiG's analysis. These medications have not been approved for the treatment of mild cognitive impairment in Germany and are not part of the standard treatment there.

After 18 months of treatment, the study showed the following:

What are the advantages of lecanemab?

Lecanemab was found to have no advantages.

What are the disadvantages of lecanemab?

Reaction to the infusion: Early analyses suggest that lecanemab has a disadvantage here. About 27 out of 100 people who received lecanemab had a reaction to the infusion, compared to about 8 out of 100 people who did not receive lecanemab. Possible reactions to the infusion included fever and chills.

No difference

Life expectancy: Based on the study data, the researchers deduced that there was no difference in life expectancy between the groups during the 18-month study period.

Severe side effects and stopping treatment due to side effects: About 11 to 15 out of 100 people in each group had severe side effects. In total, around 3 to 4 out of 100 people in the study stopped their treatment because of side effects.

There was also no difference between the groups regarding the following aspects. IQWiG concluded this based on the responder analyses provided by the manufacturer. This kind of analysis makes it possible to see how many people's symptoms were noticeably worse after 18 months.

  • Dementia symptoms: The dementia symptoms were noticeably worse in around 10 to 12 out of 100 people, regardless of whether they had received lecanemab or a placebo. The symptoms were assessed using the CDR-SB score.
  • Memory and thinking skills: In each of the groups, the participants' memory and thinking skills became noticeably worse in around 5 out of 100 people.
  • General health: There was a noticeable decline in overall health in around 17 out of 100 people, regardless of which treatment they had received.
  • Health-related quality of life: In each of the groups, this became noticeably worse in about 10 out of 100 people.

What is still not clear?

Swelling and bleeding in the brain: The manufacturer did not provide suitable data on these side effects for the relevant subgroup of patients with mild cognitive impairment. But based on the overall evaluation of the study results, it cannot be ruled out that lecanemab causes swelling and bleeding in the brain.

The manufacturer did not provide any suitable data on the participants' independence in daily life or changes in behavior.

It is also not clear whether lecanemab has different effects in men and women or in people of different ages. The manufacturer did not provide suitable data for the relevant subgroup here.

Further information

This information summarizes the main results of a review produced by the Institute for Quality and Efficiency in Health Care (IQWiG, Germany). The review was commissioned by the German Federal Joint Committee (G-BA) as part of the “early benefit assessment of medications.” On the basis of this review and the hearings received, the G-BA will pass a resolution on the added benefit of lecanemab (Leqembi).

Institute for Quality and Efficiency in Health Care (IQWiG, Germany). Lecanemab (early Alzheimer’s disease) – Benefit assessment according to §35a Social Code Book V. Dossier assessment; Commission A25-111. 2025.

IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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Lecanemab (Leqembi) for mild cognitive impairment

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Created on December 4, 2025

Next planned update: 2028

Publisher:

Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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