Real-world implementation of lecanemab in Alzheimer's disease: A Japanese cohort

Introduction Real-world evidence for lecanemab remains limited, particularly among Asian populations. We evaluated the feasibility, safety, biomarker profiles, and short-term clinical outcomes of lecanemab in practice in Japan. Methods We screened 321 patients with early Alzheimer's disease (AD) and confirmed amyloid pathology using amyloid positron emission tomography (PET) or cerebrospinal fluid analysis. Plasma amyloid-β42/40 was assessed when available. Among these, 102 initiated lecanemab and underwent structured magnetic resonance imaging (MRI) surveillance with 6 months of follow-up. Results Most treated patients had a Clinical Dementia Rating-Global (CDR-Global) score of 0.5 (96.1%), and 6-month treatment persistence exceeded 85%. Amyloid-related imaging abnormalities (ARIA), predominantly mild and asymptomatic ARIA-H, occurred in 11.4%, whereas no cases of isolated ARIA with effusion or edema (ARIA-E) were observed. One macrohemorrhagic and two moderate-severe radiographic ARIA with hemorrhage or hemosiderin deposition (ARIA-H) developed, which led to discontinuation of the treatment. Cognitive and functional measures remained generally stable over 6 months, with changes comparable to those reported in the phase 3 CLARITY-AD trial. Plasma-PET discordance highlighted the complementary value of multimodal biomarker interpretation. Discussion Lecanemab was feasible and generally well tolerated under structured MRI monitoring in routine Japanese practice.