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Enhanced Efficacy of Lecanemab: Results from AAIC 2025

Key Findings Presented

At the Alzheimer's Association International Conference (AAIC) in 2025, BioArctic's partner Eisai unveiled compelling four-year data on the drug Lecanemab (Leqembi®), emphasizing its clinical potential and robust safety profile. The findings included an extensive examination of both a phase 3 open-label extension study and various real-world evidence studies, further solidifying lecanemab's importance in combating Alzheimer's disease.

Long-Term Treatment Benefits

One of the standout conclusions from the four-year data was the ability of lecanemab to significantly extend the time patients remain in the early stages of Alzheimer's compared to the typical progression of the disease. The core phase 3 Clarity AD study indicated a meaningful reduction in cognitive decline; patients treated with lecanemab experienced a 27% slower cognitive decline according to the Clinical Dementia Rating-Sum of Boxes (CDR-SB) compared to those on a placebo. Such findings could equate to a delay of roughly a year in disease progression, which is particularly notable in patients with mild cognitive impairment (MCI).

Moreover, after three years of treatment, patients exhibited a decline measured as 1.01 points lower on the CDR-SB than expected in untreated cohorts, with the benefit growing even more pronounced after four years. Notably, among those with low tau levels, indicative of early-stage Alzheimer's, improvements were recorded in more than half of the participants.

Safety Profile Consistency

Importantly, lecanemab's safety profile remained consistent throughout the open-label extension, with no new safety concerns emerging. Over the four-year period, cases of amyloid-related imaging abnormalities (ARIA) were observed to decrease following the first year of treatment, further reinforcing the drug's safety over extended use.

Real-World Data Supports Efficacy

In addition to the clinical data, interim results from a retrospective real-world study across various centers in the U.S. revealed that a substantial 84% of patients remained stable or improved during treatment with lecanemab. The study encompassed 178 patient cases, highlighting that a majority of those receiving extensive treatment (40 or more doses) transitioned from mild Alzheimer's to MCI, demonstrating a notable impact from prolonged treatment duration.

Subcutaneous Dosing: A New Frontier

Eisai is also exploring subcutaneous (SC) dosing options for lecanemab, which shows potential to streamline the treatment process. Preliminary findings indicate that transitioning to a weekly SC autoinjector dose of 360 mg after an initial 18 months of intravenous treatment maintains comparable clinical benefits. This SC administration could enhance patient convenience and compliance by allowing treatment at home without the need for infusion center visits.

Collaborative Efforts and Future Directions

Eisai leads the global development and commercialization efforts for lecanemab, while BioArctic retains rights for its commercialization in the Nordic regions. Both companies are preparing for a joint market introduction geared towards maximizing the drug's potential in Alzheimer's therapy.

As the final results from ongoing studies are anticipated by the end of 2025, lecanemab continues to position itself as a groundbreaking treatment option in the fight against Alzheimer's disease. The collaboration between BioArctic and Eisai showcases a commitment to innovative research in neurodegenerative disorders, promising hope for patients and families affected by this challenging condition.

With a strong foundation in clinical research and ongoing studies aimed at better understanding the drug’s long-term impact and optimal administration methods, Lecanemab stands out as a beacon of progress in Alzheimer’s treatment, providing renewed optimism for those facing early-stage disease.