TOKYO and CAMBRIDGE, Mass. – Eisai Co., Ltd. and Biogen Inc. announced the results of a significant two-year real-world study of lecanemab (LEQEMBI®), an antibody aimed at combating Alzheimer’s disease (AD), during the Alzheimer’s Association International Conference (AAIC) 2025 in Toronto.
This study revealed that lecanemab has a dual action in treating Alzheimer’s, addressing both amyloid plaque and protofibrils.
The study involved a retrospective examination of clinical treatments with lecanemab across 15 medical centers in the U.S. with findings to be published in the third quarter of Eisai’s fiscal year ending March 31, 2026.
Current results serve as an interim report as of July 1, 2025.
At the baseline, this interim study assessed 178 individuals diagnosed with early Alzheimer’s disease from nine medical centers.
The demographics showed that 57.6% of the patients suffered from mild cognitive impairment (MCI) due to Alzheimer’s, while the remaining 42.4% were categorized as having mild Alzheimer’s.
The average age of the patients was 74.2 years, with a relatively balanced gender ratio of 44.6% men to 55.4% women.
Patients had been treated with lecanemab for an average of 375.4 days, reflecting an average time of 224.2 days from diagnosis to first treatment.
On average, patients received approximately 24.8 doses. At the time of the reporting, an impressive 87.4% of patients were still undergoing treatment.
Adverse events that led to treatment discontinuation were minimal, with only 1.1% of patients experiencing ARIA-E (ARIA-edema/exudation), another 1.1% facing ARIA-H (ARIA-cerebral microbleeds), and 0.6% encountering both conditions.
Additionally, 6.3% interrupted their treatment due to personal reasons or at the discretion of their healthcare provider.
The data indicated that a substantial 83.6% of the patients maintained their clinical stage, or showed improvement, with 76.9% remaining stable and 6.7% improving from mild dementia to MCI.
Moreover, an impressive 86.7% of patients who received 40 or more doses remained stable or improved, with 66.7% stable and 20.0% clinically improved at the time of the interim data cut.
Among the 178 participants, 23 individuals (12.9%) exhibited ARIA, with 14 cases identified as ARIA-E; notably, 12 were asymptomatic.
ARIA-H was detected in 11 (6.2%), with all cases remaining asymptomatic, and infusion reactions occurred in four patients (2.2%).
Importantly, no serious bleeding events or deaths were reported during this study.
The analysis further looked into the impact of APOE4 status among the 178 studied patients, where 12 were excluded due to unknown status.
Of the remaining 166 individuals, 30 (18.1%) were found to be APOE ε4 homozygotes, while 84 (49.4%) were heterozygotes, and 54 (32.5%) were non-carriers.
The incidence of ARIA was noted at 20.0% in homozygous carriers, 9.8% in heterozygous carriers, and 14.8% in non-carriers, which showcased variability in response rates.
The incidence rates for ARIA-E and ARIA-H were 13.3% and 10.0%, respectively, remaining within the FDA-approved label range for the treatment.
The majority of ARIA cases were asymptomatic at a low occurrence rate (0.13%), raising the debate about the safety profile of lecanemab.
The data also highlighted that the incidence of adverse events leading to discontinuation varied, showing 16.7% in homozygous carriers against lower incidences in heterozygous (2.4%) and non-carriers (5.6%).
Over three-quarters of patients with homozygous status (73.3%) maintained stable or improved clinical stages, supported by 88.0% of heterozygous patients and 85.2% of non-carriers.
In terms of diagnostic methodology, the study involved the utilization of blood-based biomarkers (BBMs), with 27.5% of patients diagnosed using BBMs.
In some cases, 6.1% of patients also used BBMs for confirmatory diagnosis, reflecting the growing importance of these biomarkers in clinical practices.
Clinical support data indicated that the volume of BBM tests doubled every four to eight months, accelerating particularly for p-tau217 tests.
Patient and physician satisfaction concerning lecanemab treatment was assessed through a comprehensive survey as part of the study.
Nine U.S. physicians provided insights, revealing a high average satisfaction level concerning treatment efficacy and safety, scoring 8.7 out of 10.
Specific areas rated included cognitive function (8.1), daily activity function (8.1), neuropsychiatric symptoms (7.9), and overall quality of life (8.0).
Physicians rated patient satisfaction at 8.8 on average, whereas care partners scored their satisfaction at 8.2, underscoring overall positive perceptions of lecanemab’s efficacy and safety.
While the interim findings paint a promising picture for lecanemab, Eisai cautioned that retrospective real-world studies can present challenges, such as potential biases and data consistency issues.
Results may be limited as there was no control group involved in the study, and confounding variables could have influenced outcomes.
To mitigate data inconsistencies, standardized electronic case-report forms were utilized to streamline reporting across diverse sites.
Overall, these results emphasize lecanemab’s potential as a game-changing treatment in the fight against Alzheimer’s disease, further building on the findings from prior clinical trials.
Lecanemab was initially approved in the U.S. in July 2023 for early-stage Alzheimer’s treatment and is now under regulatory review in multiple countries.
Eisai retains primary responsibility for lecanemab’s development and regulatory submissions, sharing commercial responsibilities with Biogen.
As the understanding of Alzheimer’s disease evolves, the collaboration between Eisai and Biogen, initiated in 2014, suggests a continued commitment to advancing treatment options for patients facing this challenging condition.
With ongoing clinical trials, including AHEAD 3-45 and the Tau NexGen studies, the hope is that lecanemab will serve a critical role in future Alzheimer’s therapies.
For more information on Eisai and Biogen, interested parties can access their respective websites and social media channels.
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