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Eisai Details Continued Leqembi Development Plans, Including New Dosing, Delivery Methods

Digital tablet with brain x-ray on screen

NEW YORK – Eisai on Friday outlined plans for continued commercial development of its beta-amyloid-targeting Alzheimer's disease treatment Leqembi (lecanemab).

Leqembi, a monoclonal antibody developed by Eisai and Biogen, initially garnered accelerated approval from the US Food and Drug Administration in January 2023 based on its ability to clear beta-amyloid, proteins known to form plaques that are a hallmark of Alzheimer's disease. That was converted to a full approval in July after the companies submitted data demonstrating that Leqembi had slowed Alzheimer's progression, paving the way for reimbursement by Medicare. The drug has also been approved in Japan and China.

Leqembi, indicated for adult Alzheimer's patients with mild cognitive impairment or mild dementia and with confirmed presence of elevated beta-amyloid, is administered with an intravenous infusion every two weeks. However, there has been uncertainty around how long patients should be on treatment, and whether they can stop receiving infusions once they reach amyloid clearance.

Eisai, which leads development and regulatory submissions for Leqembi, is preparing to file an application seeking FDA approval for a version of Leqembi as a maintenance treatment for Alzheimer's disease "soon," Eisai CEO Haruo Naito said through an interpreter during a webcast investor's meeting at the company's Tokyo headquarters. For that indication, patients would receive a lower dose of about half the typical dosage after 18 or 24 months on treatment.

The company is aiming to launch that maintenance treatment in Q3 of the company's fiscal 2024, which begins in April.

Eisai and Biogen are also working on a subcutaneous formulation of Leqembi for which Eisai expects to submit an application to the FDA by the end of the month, and which they said will be more convenient and less burdensome to administer than the intravenous version. Naito said the company hopes to get approval from the FDA for the subcutaneous formulation as part of the maintenance treatment in the second half of its fiscal 2024, and approval for the subcutaneous formulation for the entire treatment period — from initial dosing into maintenance dosing — in fiscal 2025.

Those changes to dosage and administration are a key factor to "increasing the value of Leqembi," Naito said.

Eisai also is in the midst of a Phase III study, called AHEAD 3-45, to investigate whether Leqembi can be administered earlier to patients with elevated levels of beta-amyloid, but without Alzheimer's symptoms, to delay or prevent cognitive decline. Eisai hopes to receive approval for an asymptomatic Alzheimer's indication in fiscal 2028.

Naito suggested that Leqembi will likely see a boost from wider usage of blood-based biomarker tests, either to prescreen patients before they undergo more expensive or intensive established methods of detecting beta-amyloid, like PET scans and cerebrospinal fluid (CSF) analyses, or to eventually supplant those methods. The availability of blood-based biomarker tests and the subcutaneous formulation of the drug could increase access to Leqembi by enabling primary-care physicians to diagnose and treat patients down the line, potentially as soon as fiscal 2027, he said. Eisai earlier this week announced it is investing up to $15 million in C2N Diagnostics, a developer of blood-based biomarker tests for Alzheimer's. 

In 2023, Eisai recorded roughly $10 million in product revenue for Leqembi, Biogen said in its 2023 earnings results released last month. As of January 2024, about 2,000 patients are on Leqembi, according to an Eisai presentation for investment analysts in February.

Leqembi marks Eisai and Biogen's second anti-amyloid Alzheimer's drug, following the controversial approval of Aduhelm (aducanumab) in 2021, which the FDA greenlighted despite mixed evidence and concerns raised by an agency advisory committee. Biogen has since discontinued development and commercialization of Aduhelm, with rights returning to the drug's original developer, Neurimmune.

Eisai is also investigating other biomarker-targeted treatments for Alzheimer's, including an investigational therapy, E2814, targeting MTBR-tau, another pathology associated with Alzheimer's. E2814 is being studied in a Phase I/II study of patients with dominantly inherited Alzheimer's, and the company is aiming for approval in fiscal 2030, Naito said.

"We believe that it can be a flagship drug on par with Leqembi," he added.