Long-term LEQEMBI® treatment slows Alzheimer’s disease progression – a hope for longevity!

The latest clinical data presented at the Clinical Trials of Alzheimer’s Disease (CTAD) conference has given a beacon of hope in curbing the progression of Alzheimer’s disease when treatment is started at an early stage.

LEQEMBI® (Lecanemab-irmb) is a result of a strategic research alliance between Eisai and BioArctic - a humanized IgG1 monoclonal antibody designed to selectively target soluble, aggregated amyloid-β (Aβ) species, including amyloid plaques and particularly Aβ protofibrils, which are believed to be among the most neurotoxic forms of Aβ in Alzheimer’s disease (AD).

Latest Clinical Data (Summary) –

1.       Benefits of Lecanemab Treatment in Slowing Disease Progression

The impact of lecanemab treatment on slowing the progression of Alzheimer's disease (AD) was evaluated using data from the Clarity AD Open Label Extension (OLE) and 16 clinical trials involving monoclonal antibodies for AD. This analysis specifically focused on the long-term progression of the disease.

The comparative analysis was conducted in two groups:

A) Mild Cognitive Impairment (MCI) due to AD that progresses to Mild AD

B) Mild Cognitive Impairment (MCI) due to AD that progresses to Moderate AD

The study examined the progression of the disease—referred to as "time savings"—in comparison to the natural decline observed in an untreated group, utilizing data from the Alzheimer's Disease Neuroimaging Initiative (ADNI). The Clinical Dementia Rating - Sum of Boxes (CDR-SB) was used as the measurement tool.

In Group A, the difference in the time taken to progress from MCI to Mild AD between the lecanemab treatment group and the untreated group was approximately 2.5 years. In Group B, the difference for progression to Moderate AD was around 3.5 years, indicating a significant reduction in disease progression.

Notably, in patients with low amyloid levels (amyloid PET < 60 centiloids), the results were even more significant, showing savings of about 6 years in progression from MCI to Mild AD and 8.3 years from MCI to Moderate AD.

2.      Lecanemab Subcutaneous Formulation for Treatment Initiation in Early Alzheimer’s Disease (in comparison to intravenous dosing)

In 2024, a study by Honig et al. reported safety results for Lecanemab treatment, given through an intravenous (IV) infusion of 10 mg/kg every two weeks. The study involved 1,795 main participants (from the initial 18-month clinical trial) and 1,612 participants who continued treatment after that period.

In the continuation group, the most common side effects from Lecanemab included reactions from the infusion, ARIA with hemosiderin deposits (ARIA-H), small bleeding in the brain (microhemorrhages), ARIA with edema (ARIA-E), and headaches.

Recent findings from the lecanemab subcutaneous (SC) clinical program showed results from an open-label extension of the Clarity AD trial, focusing on a subset of 273 patients. The study found that administering 500 mg subcutaneously every week (using two 250 mg injections) is similar to the IV dosing of 10 mg/kg every two weeks. Both methods have the same effectiveness and safety profile.

The effect on removing amyloid and the occurrence of ARIA-E were similar for both administration routes, with ARIA-E occurring in 12.4% of patients overall and 30.9% in ApoE4 homozygotes. In patients who previously received lecanemab, 0% in the 500 mg SC group had systemic infusion reactions, compared to 26.4% in the IV group. The rate of anti-drug antibodies (ADA) was low at 1.4%.

Overall, subcutaneous forms of lecanemab have the same effectiveness with fewer systemic infusion reactions and are as effective as traditional IV administration, making it more convenient for patients.

In Brief – what we know about Lecanemab subcutaneous autoinjector?

In July 2025, new data presented at the AAIC demonstrated the efficacy of the investigational LEQEMBI® (lecanemab-irmb) 360 mg subcutaneous autoinjector. The data also indicate that the 500 mg subcutaneous autoinjector provides equivalent exposure to the initial treatment regimen of 10 mg/kg intravenous administration every two weeks for up to 18 months, specifically in terms of amyloid removal, efficacy, and ARIA-E. For further details, please check my News and Opinion section here.

Conclusion –

·       Recent findings indicate that long-term treatment with LEQEMBI may have the ability to delay the progression of mild cognitive impairment (MCI) to moderate Alzheimer’s disease by as much as 8.3 years in patients with low amyloid levels who begin treatment at an early stage.

·       New safety and efficacy data regarding a subcutaneous formulation for initiating LEQEMBI treatment were presented at a recent scientific symposium. This formulation is currently undergoing regulatory review in the United States.

·       In light of the recent setbacks in clinical trials for other groundbreaking Alzheimer’s treatments, the collaboration between Eisai and Biogen stands out as a success story.