Although clinical trials have suggested a lower incidence of adverse events associated with Lecanemab in Asian populations compared to global cohorts, longitudinal real-world data across broader clinical indications are necessary to confirm these findings in routine practice. This study aimed to provide real-world evidence regarding the safety profile of Lecanemab in Japanese patients in a clinical setting. A real-world observational study with a follow-up period of up to 18 months. A single center in Japan. We included 120 Japanese patients who received Lecanemab between December 2023 and November 2025 and underwent at least one brain MRI before the fifth infusion. Safety outcomes included amyloid-related imaging abnormalities (ARIA), infusion-related reactions (IRRs), and treatment discontinuation. The mean age was 74.2 ± 7.9 years, and 89 (74%) were female. The majority of patients (88%) had a baseline CDR global score of 0.5. During follow-up, 81 patients completed the 12-month assessment. ARIA occurred in 24 patients (20%); ARIA-E with or without ARIA-H occurred in 5 patients (4%), and isolated ARIA-H occurred in 19 patients (16%). Crucially, no patients experienced symptomatic ARIA. All patients with ARIA-E who had available APOE data were ε4 carriers. Patients with ARIA had significantly lower baseline MMSE scores ( p = 0.04), alongside non-significant trends toward higher plasma GFAP levels ( p = 0.11) and higher deep white matter Fazekas scores ( p = 0.05). IRRs occurred in 34 patients (28%), all of which were mild. Treatment was discontinued in 19 patients (16%), mainly due to disease progression ( n = 8). In this Japanese AD cohort, Lecanemab demonstrated a manageable safety profile in a real-world setting. In exploratory analyses, potential trends toward a higher frequency of ARIA were observed in patients with lower MMSE scores, higher plasma GFAP levels, and higher Fazekas scores, underscoring the importance of individualized risk assessment prior to therapy.
Shimasaki et al. (Sat,) studied this question.