To evaluate the benefit of continued treatment with lecanemab using a more clinically meaningful metric than the continuous outcome measures often used as primary endpoints in clinical trials, especially in a group with low baseline amyloid.

Lecanemab is an Ab-targeting therapy that was evaluated in the CLARITY-AD study and has been shown to slow cognitive and functional decline in early AD. The primary endpoint for the CLARITY-AD trial was the change in CDR-SB.

Using data from CLARITY-AD OLE, the Time Component Test was used to convert clinical decline by CDR-SB into an estimate of time saved over 36–48 months of lecanemab treatment. Both the full population (48-months) and a low-amyloid sub-group (<60 Centiloids at baseline; 36-months) were analyzed. The full treated OLE population was compared to two separate historical, matched external control populations from ADNI and BioFinder1. A sub-group of participants from ADNI with <60 Centiloids at baseline was also used for comparison.

In the full treated population, lecanemab led to 7.3 or 7.8 months of time savings after 36 months and 11.0 or 13.1 months after 48 months compared to ADNI or BioFinder1, respectively. The low-amyloid sub-group treated with lecanemab showed a greater benefit, achieving 17.4 months of time savings at 36 months vs. the matched, low-amyloid ADNI group. When the treated low-amyloid group was compared to the ADNI and BioFinder1 groups that were matched to the full population, the estimated time savings with lecanemab at 36 months was 20.6 and 21.2 months, respectively.

The CLARITY-AD OLE study demonstrated that lecanemab's treatment benefit continues to meaningfully accumulate when continued past the expected time for plaque clearance. The substantially greater time savings in the low-amyloid group suggests that treating at an earlier stage leads to greater benefit, highlighting the importance of timely diagnosis and treatment initiation.