Eisai and BioArctic have received approval for the Alzheimer’s disease drug Leqembi (lecanemab-irmb) in Japan, making it the second country to gain access to the treatment.

Leqembi is a monoclonal antibody that targets and reduces insoluble amyloid-beta (Aβ) forms in the brain. It is the first and only approved treatment that has demonstrated a reduction in the rate of disease progression in patients with Alzheimer’s.

The Japanese approval unlocked a milestone-based payment of EUR 17m ($18m) to BioArctic.

The approval is based on Phase III data from the Clarity AD trial (NCT03887455) led by Eisai that showed that treatment with Leqembi reduced clinical decline in patients by 27% at 18 months compared to the placebo.

The prescribing information for Leqembi includes a warning for amyloid-related imaging abnormalities (ARIAs), a concern for Alzheimer’s patients taking certain medication. Last week, BrainScope announced an investment from the Alzheimer’s Drug Discovery Foundation (ADDF) to pursue the development of a biomarker that could detect ARIAs in to reduce the number of magnetic resonance imaging (MRI) scans required for patients who suffered a concussion.

Leqembi was awarded a full traditional approval in the US in July 2023.

Co-founder of BioArctic and inventor of Leqembi Professor Lars Lannfelt said, in a statement to Pharmaceutical Technology, “The approval of Leqembi, first in the USA and now in Japan, is a paradigm-shifting step in the fight against Alzheimer’s disease.”

According to GlobalData, the AD market in Japan will be worth $957.7M in 2030, with Leqembi being the highest selling drug, generating $204.3 million in sales.

GlobalData is the parent company of Pharmaceutical Technology.