BioArctic's AB partner Eisai presented new data at the 2026 International Conference on Alzheimer's and Parkinson's Diseases and related neurological disorders (AD/PDTM), held in Copenhagen, Denmark March 17-21. Eisai presented new real-world findings from an analysis of long-term treatment persistence among early Alzheimer's disease patients in the United States receiving intravenous (IV) lecanemab. Based on data from the PurpleLab CLEAR Claims database, the analysis showed that most patients continued lecanemab therapy after the initial 18 months of treatment (78.4% of individuals continued lecanemab treatment at 18 months, 71.7% at 20 months, and 67.3% at 24 months).
The results are similar to what was seen in the Phase 3 Clarity AD study where 94% of patients who completed 18 months of lecanemab treatment chose to continue maintenance treatment by enrolling in the subsequent open-label, long-term extension (OLE) study. In the OLE study, patients who stayed on treatment continued to benefit from four years of lecanemab treatment compared with the natural course of Alzheimer's disease (ADNI). Professor Lars Lannfelt, BioArctic's co-founder, delivered an oral presentation about the binding profile of lecanemab in Alzheimer's disease brain tissue, demonstrating its selective targeting of soluble amyloid-beta (Aß) protofibrils.
He described the mechanisms of action, showing how lecanemab engages immune pathways to promote clearance of Aß. Ebba Amandius from BioArctic also presented a poster that showed the successful use of a screening strategy in the ongoing exidavnemab trial in Parkinson's disease and multiple system atrophy (EXIST), applying alpha-synuclein seed amplification assay (SAA) for patient stratification between placebo and treatment arms. The approach enabled even distribution of participants with alpha-synuclein pathology between arms while still allowing timely randomization. It highlights the feasibility and importance of SAA testing during screening in clinical trials targeting alpha-synuclein.
Lecanemab is the result of a long-standing collaboration between BioArctic and Eisai, and the antibody was originally developed by BioArctic based on the work of Professor Lannfelt and his discovery of the Arctic mutation in Alzheimer's disease. This release discusses investigational uses of an agent in development and is not intended to convey conclusions about efficacy or safety. There is no guarantee that such investigational agents will successfully complete clinical development or gain health authority approval.
Leqembi is the result of a strategic research alliance between BioArctic and Eisai. It is a humanized immunoglobulin gamma 1 (IgG1) monoclonal antibody directed against aggregated soluble (protofibril) and insoluble forms of amyloid-beta (Aß). Leqembi is approved in 53 countries and is under regulatory review in 6 countries.
Following the initial phase with treatment every two weeks for 18 months, intravenous (IV) maintenance dosing with treatment every four weeks is approved in 7 countries, including the United Kingdom, China, the US and Japan, and applications have been filed in 10 countries and regions. In the US, Leqembi Iqlik is approved for subcutaneous dosing with an autoinjector for maintenance treatment of early Alzheimer's disease. In November 2025, a new drug application for subcutaneous formulation of Leqembi was submitted in Japan.
In December 2025, Leqembi was included in the Commercial Insurance Innovative Drug List, recently introduced by the National Healthcare Security Administration (NHSA) of China. In January 2026, Eisai's supplemental Biologics License Application regarding a subcutaneous starting dose with Leqembi Iqlik was granted Priority Review by the US FDA with a May 24, 2026, PDUFA date. In January 2026, the Biologics License Application for subcutaneous formulation of Leqembi was accepted in China and in February, the application was designated for priority review.
Since July 2020, Eisai's Phase 3 clinical study (AHEAD 3-45) with lecanemab in individuals with preclinical Alzheimer's disease meaning they are clinically normal and have intermediate or elevated levels of amyloid in their brains, is ongoing. The study was fully recruited in October 2024. AHEAD 3-45 is a four-year study conducted as a public-private partnership between Eisai, Biogen and the Alzheimer's Clinical Trial Consortium that provides the infrastructure for academic clinical trials in Alzheimer's disease and related dementias in the US, funded by the National Institute on Aging, part of the National Institutes of Health.
Since January 2022, the Tau NexGen clinical study for Dominantly Inherited Alzheimer's disease (DIAD), that is conducted by Dominantly Inherited Alzheimer Network Trials Unit (DIAN-TU), led by Washington University School of Medicine in St. Louis, is ongoing and includes lecanemab as the backbone anti-amyloid therapy.
