How effective is Leqembi in delaying Alzheimer's disease?

Leqembi (lecanemab-irmb) is a monoclonal antibody that may be used to treat Alzheimer’s disease. It targets and removes amyloid beta in the brain, which is thought to contribute to Alzheimer’s disease. Studies of people taking the medication for up to 18 months have shown it delays cognitive decline by 5.3 months compared to placebo.

Leqembi is FDA approved to be started in people with mild cognitive impairment or mild dementia. It is given as an intravenous infusion once every 2 weeks. It is not a cure for Alzheimer’s disease, but it may slow down the progression of symptoms when taken in the early stages. It currently is not approved for people who are farther along in the stages of Alzheimer’s disease.

In January 2023, Leqembi was approved under the FDA’s Accelerated Approval pathway. In July 2023, the FDA converted it to traditional approval based on additional data from a clinical trial. Data from studies as long as 18 months have been published. How well Leqembi works beyond this time is not known.

How effective is Leqembi?

Clinical trials have shown that Leqembi is more effective than placebo (no active medication) at reducing brain amyloid plaque. Amyloid plaques are a hallmark sign of Alzheimer’s disease, and are thought to play a role in problems with brain function. People taking Leqembi also had slower cognitive decline compared to people taking placebo.

Study 1: 856 participants received Leqembi or a placebo every 2 weeks. At week 53, participants taking Leqembi had a 64% likelihood of 25% or more slowing of cognitive decline. This was based on scores from different tests, including the Clinical Dementia Rating scale Sum of Boxes (CDR-SB), MMSE, and Alzheimer Disease Assessment Scale – Cognitive Subscale 14 (ADAS-Cog 14). Leqembi reduced more amyloid plaques in the brain compared to placebo.

Study 2 (Clarity AD): In an effort to verify the initial positive results found during Study 1, 1,795 participants with Alzheimer’s disease were randomly assigned to take Leqembi or a placebo once every 2 weeks. Compared to placebo, participants taking Leqembi had 27% slower cognitive decline at 18 months. This means that people taking Leqembi took 5.3 months longer to reach the same decline in cognition and function as placebo.

Changes from baseline in cognition and function were assessed using CDR-SB, ADAS-Cog14, and Alzheimer's Disease Cooperative Study-Activities of Daily Living Scale for Mild Cognitive Impairment (ADCS MCI-ADL). Leqembi also reduced brain amyloid plaques more than placebo.

• CDR-SB: The CDR-SB is a score that helps stage the severity of cognitive impairment. There was a 27% difference between Leqembi and placebo on the increase in score. Those taking Leqembi had an initial score of 3.17, and after 18 months saw a 1.21 increase. Participants taking placebo had an initial score of 3.22 and saw an increase of 1.66.
• ADAS-Cog14: The ADAS-Cog 14 is a tool used to measure cognition and assess the decline in language and memory in people with dementia. There was a 26% difference between Leqembi and placebo on the increase in score. Participants taking Leqembi had an initial score of 24.45 and saw an increase of 4.140 at 18 months. Those taking a placebo had an initial score of 24.37 and saw an increase of 5.581.
• ADCS MCI-ADL: The ADCS MCI-ADL is a tool that measures the ability to perform activities of daily living. There was a 37% difference between Leqembi and placebo on the decrease in score. Participants taking Leqembi had an initial score of 41.2 and saw a decrease of 3.5. Those taking a placebo had an initial score of 4.9 and saw a decrease of 5.5.

This is not all the information you need to know about Leqembi (lecanemab) for safe and effective use and does not take the place of your doctor’s directions. Review the full product information and discuss this information and any questions you have with your doctor or other health care provider.

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