Swedish research-based biopharma company BioArctic AB (STO:BIOA-B) and its Japanese partner Eisai Co Ltd (TYO:4523) on Thursday reported new data on lecanemab (Leqembi) showing potential to delay progression from mild cognitive impairment to moderate Alzheimer's disease by up to 8.3 years in patients with low amyloid who begin treatment early.

The findings were presented at the 18th Clinical Trials in Alzheimer's Disease (CTAD) conference, held in San Diego on 1-4 December.

Additional presentations highlighted the subcutaneous autoinjector formulation, approved in the United States for maintenance treatment in August 2025, with a supplemental application for initiation dosing completed in November and a Japanese submission made the same month.

Real-world data from multiple countries continued to demonstrate clinical benefit and a safety profile consistent with the phase 3 Clarity AD study.

A 10-year modelling analysis using Clarity AD extension data suggests that long-term Leqembi therapy may slow cognitive decline compared to natural disease progression, with early initiation offering the greatest time savings. In untreated patients, progression from mild cognitive impairment to mild Alzheimer's occurred in 7.2 years, versus 9.7 years with continued treatment, while low-amyloid patients saw progression extend to 13.2 years.

Time to moderate Alzheimer's was 10.1 years in untreated patients and 13.6 years with treatment, rising to 18.4 years in the low-amyloid group.

Separate findings showed that weekly 500 mg subcutaneous dosing achieved bioequivalent drug exposure to biweekly intravenous administration, with similar efficacy, safety, and predicted ARIA-E incidence.

Systemic infusion reactions were markedly lower with the subcutaneous regimen, supporting its potential as a more convenient treatment option within BioArctic and Eisai's ongoing commercialisation collaboration.