TOKYO and CAMBRIDGE, Mass., July 31, 2025 - (JCN Newswire) - Eisai Co., Ltd. (Headquarters: Tokyo, CEO: Haruo Naito,“Eisai”) and Biogen Inc. (Nasdaq: BIIB, Corporate headquarters: Cambridge, Massachusetts, CEO: Christopher A.Viehbacher, “Biogen”) announced today that the two-year real-world study in the U.S of lecanemab (generic name, product name: LEQEBMI®), an anti-AB protofibril* antibody, was presented at the Alzheimer's Association International Conference (AAIC) 2025, held in Toronto, Canada and virtually. Only lecanemab fights AD in two ways– targeting both amyloid plaque and protofibrils*, which can impact tau downstream.

Lecanemab received traditional approval in the U.S. in July 2023 for the treatment of early Alzheimer's disease (AD). This retrospective study was conducted to investigate the actual state of real-world clinical treatment with lecanemabat 15 medical centers in the U.S., with a final report scheduled for late in the third quarter of Eisai’s fiscal year ending March 31, 2026. This presentation serves as an interim report as of July 1, 2025.

Patient Baseline and Actual Treatment Situation The interim study collected information on 178 people living with early AD from nine US medical centers using a standardized case report format. The disease stage of the patients at baseline was mild cognitive impairment (MCI) due to AD in 57.6% and mild AD in 42.4%. The average age of the patients was 74.2 (±6.6) years, and the ratio of men to women was 44.6 to 55.4.

The mean duration of lecanemab treatment was 375.4 days (± 182.8 days). The mean time from diagnosis to first treatment was 224.2 days (± 295.4 days) and the mean number of lecanemab treatments was 24.8 (± 11.5). At the time of case reporting, 87.4% of patients (152 patients) were continuing treatment with lecanemab. Adverse events leading to discontinuation of treatment included ARIA-E (ARIA-edema/exudation) in two patients (1.1%), ARIA-H(ARIA-cerebral microbleeds, cerebral hemorrhage and superficial hemosiderin deposition) in two patients (1.1%),and concomitant ARIA-E and ARIA-H in one patient (0.6%). Three patients (1.7%) discontinued due to adverse events other than ARIA. In addition, 11 patients (6.3%) reported discontinuing the treatment for personal reasons or at the discretion of their doctor or the individual.

In this study, 83.6% of patients either remained at the same clinical stage or improved from mild dementia to MCI (stable: 76.9%, improvement: 6.7%). Additionally, at time of interim data cut, 86.7% of patients who had received 40 or more doses over 18 months remained stable or showed clinical improvement (stable: 66.7%,improvement: 20.0%:).

Of the 178 patients, ARIA was observed in 23 (12.9%). 14 (7.9%) were observed to have ARIA-E, of which 12(6.7%) were asymptomatic. ARIA-H was present in 11 patients (6.2%), all of whom were asymptomatic. Infusion reactions were observed in four patients (2.2%). Additionally, no serious bleeding events or deaths were reported. 

Impact of APOE4 Status Of the 178 patients in this study, 12 were excluded with unknown status. Among the remaining 166 patients,30 (18.1%) were APOE 4 homozygotes, 84 (49.4%) were heterozygotes, 54 (32.5%) were non-carriers. Generally, the proportion of homozygotes among people with AD is thought to be 15% or more.

The incidence of ARIA was 20.0%, 9.8% and 14.8% in homozygous carriers, heterozygous carriers and noncarriers, respectively (45.0%, 19.0% and 13.0% respectively in the Phase 3 Clarity AD 18-month core study). The incidence rate of ARIA-E and ARIA-H were 13.3% and 10.0%, respectively (32.6% and 39.0% in the Clarity AD core study), which is within the FDA-approved label range. The majority of ARIA cases (0.13%) were asymptomatic. The incidence of adverse events leading to discontinuation was 16.7% in homozygous carriers,2.4% in heterozygous carriers and 5.6% in non-carriers.

73.3% of homozygote patients’ clinical stage remained stable or improved (stable: 66.6%, improved: 6.7%),88.0% of heterozygotes patients’ clinical stage remained stable or improved (stable: 83.0%, improved: 4.9%)and 85.2% of non-carrier patients’ clinical stage remained stable or improved (stable: 75.9%, improved: 9.3%).

Utilization of Blood-Based Biomarkers (BBMs)BBMs are being developed in AD to identify brain AB pathology and are intended for use in prescreening (triage)and confirmatory diagnosis. Of the 178 patients in this study, 49 patients (27.5%) were diagnosed using BBMs. In some of these cases (11 patients, 6.1%), it was also used for confirmatory diagnosis. Data collected from clinical practices showed the volume of tests doubling every 4 to 8 months, with BBMs using p-tau217 growing most rapidly.

Satisfaction with Lecanemab Treatment The results of a physician, patient and care partner lecanemab satisfaction survey was presented. The survey was based on questionnaires and interviews with nine U.S. physicians and evaluated treatment from multiple perspectives, including efficacy, safety and quality of life (QOL).

In the physicians’ evaluation, the average satisfaction level for the treatment efficacy and safety (out of 10) was8.7. The scoring criteria included: cognition 8.1, daily function 8.1, behavioral/neuropsychiatric symptoms 7.9and QOL 8.0. The satisfaction level of the patients as assessed by physicians was 8.8, and that of the care partners was 8.2. These results highlight the favorable evaluation of lecanemab’s efficacy and safety in real world clinical practice and reinforce its therapeutic value.

Note: Retrospective real-world studies can be very valuable in providing additional information to complement clinical trial data. However, there may have several limitations to keep in mind:

Potential for Biases

Data Completeness and Consistency
Data may be collected inconsistently since data collection is completed by different people at independent3 sites.
* Mitigation: Data inconsistency is pursued by providing site access to standardized electronic case-report forms.

Lack of Control Group
Interpretation of data may be limited since real-world studies do not utilize placebo-controlled arms

Confounding Variables
Confounding variables are not controllable, which may impact the relationship between the exposure and outcome.

Eisai serves as the lead for lecanemab’s development and regulatory submissions globally with both companies co-commercializing and co-promoting the product and Eisai having final decision-making authority.

* Protofibrils are thought to be the most toxic AB species that contribute to brain damage in AD and play a major role in the cognitive decline of this progressive and devastating disease. Protofibrils can cause neuronal and synaptic damage in the brain, which can subsequently adversely affect cognitive function through multiple mechanisms.1 The mechanism by which this occurs has been reported not only by increasing the formation of insoluble AB plaques, but also by directly damaging signaling between neurons and other cells. It is believed that reducing protofibrils may reduce neuronal damage and cognitive impairment, potentially preventing the progression of AD.2

For more details, please visit: https://www.eisai.com/news/2025/pdf/enews202552pdf.pdf

MEDIA CONTACTS

Eisai Co., Ltd.
Public Relations Department
TEL: +81 (0)3-3817-5120

Eisai Europe, Ltd.
EMEA Communications Department
+44 (0) 797 487 9419
Emea-comms@eisai.net

Eisai Inc. (U.S.)
Libby Holman
+1-201-753-1945
Libby_Holman@Eisai.com

Biogen Inc.
Madeleine Shin
+1-781-464-3260
public.affairs@biogen.com

INVESTOR CONTACTS

Eisai Co., Ltd.
Investor Relations Department
TEL: +81 (0) 3-3817-5122

Biogen Inc.
Tim Power
+ 1-781-464-2442
IR@biogen.com

Copyright © 2025 ACN Newswire. All rights reserved. A division of Asia Corporate News Network.