Initial Real-world Experience in Using Lecanemab in Hong Kong: Safety and Preliminary PET-CT Data

Background:
Lecanemab, an anti-amyloid monoclonal antibody, is increasingly utilised as a disease-modifying therapy for early Alzheimer's disease (AD) in super-aging Asian societies. Real-world evidence iscritically needed to characterise its efficacy and safety profile in Asian populations.

Methods:
This report summarizes clinical experiences at Canossa Hospital’s outpatient department and aprivate clinic in Hong Kong. The study involved 45 patients—27 with mild cognitive impairment (MCI) and18 with early-stage Alzheimer’s disease (AD)—all of whom had diagnoses confirmed via Amyloid PETscans. Between May 11, 2024, and January 26, 2026, patients received their initial infusion of lecanemab (10mg/kg). Following standard protocols, brain MRIs were conducted at baseline and prior to the 3rd, 5th, 7th,and 14th infusions.

Results:
The cohort’s median age is 75 (range: 56-87), with a female predominance (64.4%, n=29). Twenty-five (55.6%) patients were APOE-ε4 carriers, including 18 (40.0%) heterozygotes and 7 (15.6%)homozygotes. As of 30 March 2026, treatment exposure reached at least 6 months for 32 patients (71.1%),12 months for 20 (44.4%), and 18 months for 5 (11.1%). No ARIA was detected among non-APOE- ε4carriers and heterozygotes. One asymptomatic ARIA-H with superficial siderosis was detected in an APOE-ε4 homozygote. Five patients (11.1%) discontinued treatment due to adverse events, including oneasymptomatic ARIA-H with superficial siderosis (APOE-ε4 homozygote patient), injection site extravasation,falls, skin petechiae and renal impairment. Six patients were on antiplatelet and 1 on direct oralanticoagulant treatments. Concurrent antithrombotic treatment was significantly associated with adverseevents (p=0.010), while age, sex, and APOE-ε4 status were not correlated with adverse events. Repeat PETAmyloid scans were performed in 4 patients, two of them showed complete clearance of amyloid. All fourof them did not progress in the clinical stage of AD.

Conclusion:
Our real-world experience demonstrates that lecanemab treatment in Hong Kong is generallysafe, characterized by a very low incidence of amyloid-related imaging abnormalities (ARIA). This safetyprofile is particularly evident among non-APOE-ε4 carriers and heterozygotes. These findings align with theCLARITY AD study, which also indicated that ARIA is relatively uncommon in Asian patients receivinglecanemab.