On 25 September 2023, the Japanese health ministry approved the use of Leqembi (lecanemab) in the Japanese market.

The approval of Leqembi in Japan comes nearly ten months after the drug was filed for the priority review in January 2023, making it the first approved anti-amyloid Alzheimer’s disease (AD) treatment entering the Japanese market. The agent is already in use in the US, where the FDA granted accelerated approval in January 2023 and full approval in July 2023.

The Phase III Clarity AD study (NCT03887455) demonstrated positive efficacy and clinically significant improvements for Leqembi in patients aged between 50 and 90 years old diagnosed with early Alzheimer’s disease, as the treatment reduced the disease progression rate and slowed cognitive impairment in early and mild dementia stages. Specifically, Leqembi led to the reduction of Clinical Dementia Rating Sum of Boxes by overall 27% in comparison to placebo over the course of 18 months, fulfilling its primary endpoint.

As a secondary endpoint, Leqembi improved the AD Cooperative Study-Activities of Daily Living Scale for Mild Cognitive Impairment by 37% in comparison to placebo. The most common side effects during the clinical trial were infusion-related reactions (26.4% Leqembi vs. 7.4% placebo) and amyloid-related imaging abnormalities (ARIA) with edema or effusion (12.6% Leqembi vs. 1.7% placebo).

While this approval is important for a country like Japan, with a large aging population, the reduction in clinical decline shown by Leqembi is still quite modest, leaving uncertainty among some physicians if it is large enough for patients to notice a real difference, particularly enough to outweigh potential health risks such as ARIA.

Eisai is still awaiting a response from the EMA about the use of Leqembi in Europe after submitting the application in January 2023. Currently, the decision from the EMA is expected in Q4 2023 or in early Q1 2024.

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By GlobalData

Leqembi could generate significant sales

Despite these uncertainties, Leqembi is the first disease-modifying therapy in the Japanese market and thus is expected to garner significant sales. According to GlobalData’s report, Alzheimer’s Disease: Eight-Market Drug Forecast and Market Analysis, Leqembi is expected to perform well in the Japanese market, generating sales of around $204 million in 2030, making it the most profitable treatment in the country.

These sales mean that Eisai will retain a dominant position within the Japanese market, especially as the company is already a large key player in the AD market with its drug Aricept, widely considered the gold-standard symptomatic therapy for AD.