Clinical Pharmacology Update: Leqembi Iqlik From Eisai

The FDA recently approved the biologics license application for once-weekly lecanemab-irmb subcutaneous injection (Leqembi Iqlik; Eisai Co, Ltd) for maintenance dosing to treat Alzheimer disease (AD) in patients with mild cognitive impairment or mild dementia stage of the disease.¹

Nearly 6.9 million individuals in the US who are 65 years and older are living with AD, with symptoms including memory loss, trouble remembering recent events or conversations, and changes in personality and behavior. The disease can also impact thinking, reasoning, and judgment and lead to difficulty with planning and performing familiar tasks.²

PHARMACOLOGY AND PHARMACOKINETICS

Lecanemab-irmb was initially approved as an intravenous (IV) infusion therapy administered via IV over 1 hour, targeting and removing amyloid-ß from the brain. The humanized IgG1 monoclonal antibody is directed against aggregated soluble and insoluble forms of amyloid-ß. With this latest FDA approval, subcutaneous lecanemab can be injected in approximately 15 seconds, addressing a crucial need for accessibility and reducing the time burden of IV infusions.¹

After 18 months of IV treatment at 10 mg/kg every 2 weeks, patients may continue IV infusions at 10 mg/kg once every 4 weeks or switch to the weekly 360-mg subcutaneous injection administered via an autoinjector.¹

CLINICAL TRIAL DATA

The initial biologics license application for subcutaneous maintenance dosing was based on findings from the open-label extension (OLE) phase of the Clarity AD trial (NCT03887455). This double-blind, placebo-controlled study confirmed the safety and effectiveness of subcutaneous lecanemab in patients with early AD. The OLE portion of the study evaluated whether the longterm safety and tolerability of the drug, as measured by the Clinical Dementia Rating Scale Sum of Boxes (CDR-SB), was maintained over the entire duration of the extension.^1,4

The primary end point of the OLE was to measure the frequency of treatment-emergent adverse events and the change in the CDR-SB score from the beginning of the study. A total of 1795 patients were included, and subcutaneous lecanemab was generally well tolerated. Of the 9 deaths that occurred during the OLE, 4 were potentially related to the drug.^3,4

CONTRAINDICATIONS, WARNINGS, AND PRECAUTIONS

Before starting lecanemab formulations, a health care provider must confirm the presence of amyloid-ß plaques, which can be done through such tools as an amyloid PET scan or a lumbar puncture. The FDA also recommends that patients undergo an MRI before starting treatment with lecanemab. Additionally, because individuals with certain APOE genotypes are at higher risk for amyloid-related imaging abnormalities (ARIA), the FDA encourages genetic testing for this status.¹

Lecanemab formulations have not been studied in individuals with more advanced stages of AD or those without clinical symptoms.^1,4

The most common adverse events in clinical trials among patients treated with subcutaneous lecanemab were infusion-related reactions, forms of ARIA, COVID-19, and headaches. ARIA events, including edema and/or effusion on MRI and microhemorrhages or superficial siderosis, were mild to moderate in severity and occurred more often in individuals who carried the APOE*E4 allele.^3,4

REFERENCES

1. US FDA approves Leqembi Iqlik (lecanemab-irmb) subcutaneous injection for maintenance dosing for the treatment of early Alzheimer’s disease. News release. Eisai Co, Ltd, and Biogen. August 29, 2025. Accessed September 17, 2025. https://investors.biogen.com/news-releases/news-release-details/fda-approves-leqembir-iqliktmlecanemab-irmb-subcutaneous

2. Alzheimer’s disease. Mayo Clinic. November 8, 2024. Accessed September 17, 2025. https://www.mayoclinic.org/diseases-conditions/alzheimers-disease/symptoms-causes/syc-20350447

3. A study to confirm safety and efficacy of lecanemab in participants with early Alzheimer’s disease (Clarity AD). ClinicalTrials.gov. Updated September 8, 2025. Accessed September 17, 2025. https://clinicaltrials.gov/study/NCT03887455

4. Lecanemab approved for treatment of early Alzheimer’s disease. Alzheimer’s Association. Accessed September 17, 2025. https://www.alz.org/alzheimers-dementia/treatments/lecanemab-leqembi