Data presented at AAIC 2026 support further evaluation of a once-weekly 500 mg autoinjector regimen as an alternative to intravenous initiation in early Alzheimer’s disease.
Eisai has presented clinical-development data showing that an investigational once-weekly subcutaneous initiation regimen of lecanemab achieved drug exposure comparable to the drug’s approved intravenous initiation regimen in people with early Alzheimer’s disease.
The findings were presented at the Alzheimer’s Association International Conference 2026 in London as part of the development programme for the Leqembi subcutaneous autoinjector.
According to Eisai and its development partner BioArctic, a fixed 500 mg subcutaneous dose administered once a week produced an exposure ratio of 104% compared with intravenous lecanemab administered at 10 mg/kg every two weeks. The reported 90% confidence interval ranged from 99.1% to 109%.
The companies said exposure remained consistent across body-weight groups. Their analyses also indicated that amyloid removal, changes measured through the Clinical Dementia Rating-Sum of Boxes and the incidence of amyloid-related imaging abnormality with oedema were associated primarily with lecanemab exposure rather than its route of administration.
These findings support the companies’ expectation that the investigational subcutaneous initiation regimen could have an efficacy and safety profile broadly comparable to intravenous initiation. However, the data should not be interpreted as evidence from a completed head-to-head clinical outcomes trial establishing equivalent efficacy and safety.
The overall safety profile reported for the subcutaneous formulation was broadly consistent with previous experience with intravenous lecanemab. Injection-related reactions were primarily local, while systemic reactions occurred less frequently. Anti-drug antibodies were reported in 1.4% of participants receiving the 500 mg regimen, and no neutralising antibodies were detected.
Eisai also presented early observational findings from two US Alzheimer’s treatment centres. At one centre, 28 patients receiving subcutaneous treatment showed slower cognitive decline over 36 months than a matched natural-history cohort. A separate case series found that 10 of 11 evaluable patients remained stable or improved on the Mini-Mental State Examination after receiving subcutaneous maintenance treatment for at least six months.
The small, non-randomised cohorts do not establish comparative clinical effectiveness and require confirmation in larger controlled studies.
Leqembi Iqlik is already approved in the US as a 360 mg weekly subcutaneous autoinjector for maintenance treatment after an initial treatment period. The proposed 500 mg weekly regimen is intended for treatment initiation and remains under review by the US Food and Drug Administration.
If authorised, the initiation regimen could allow eligible patients to receive both the starting and maintenance phases through subcutaneous administration rather than beginning treatment through fortnightly intravenous infusions.
