Study summary

Lecanemab slowed decline in early Alzheimer's by about a quarter

Clarity AD · 1,906 people · 18-month results; approved in the US in 2023

What was tested

Lecanemab, an antibody that removes amyloid from the brain, given by infusion every two weeks, against placebo in people with early Alzheimer's.

What they found

• Decline on the main memory-and-function scale was 27% slower with lecanemab, a difference of 0.45 points on an 18-point scale.
• Small brain bleeds seen on scans occurred in 17.0% with lecanemab and 8.7% with placebo; 0.7% had symptoms from them.
• Reviewers note the difference is smaller than the 1 point often considered noticeable.
• Four-year follow-up has been reported as delaying progression by close to 10 months.

What it means

The first clear proof that removing amyloid slows the disease. The effect is modest and comes with scan monitoring.