This study aimed to determine the efficacy of amyloid clearance of lecanemab in patients with Parkinson's disease (PD) with amyloid co-pathology. Lecanemab, an anti-amyloid monoclonal antibody, was apporoved by the US FDA in July 2023 and in South Korea in May 2024, as a disease-modifying therapy based on its clinical efficacy and reduction of amyloid plaques in patients with early-stage Alzheimer's disease (AD). AD pathology is also common in PD, and approximately 35% of patients with PD dementia have co-existing AD pathology. Currently, no mediations have been developed to slow the progression of PD. Therefore, this study aimed to determine whether reducing the amyloid burden in patients with PD with co-exsistent AD pathology could potentially slow disease progression. To test it, patients with PD with mild cognitive impairment or early dementia, who were confirmed to have amyloid deposition through amyloid imaging, would be enrolled as a treatment arm, and the degree of reduction of amyloid plaque after 18 months of lecanemab administration would be investigated.

This study plans to consecutively enroll the patients with Parkinson's disease (PD) who have confirmed amyloid deposition on amyloid imaging and meet the indications for lecanemab administration. After a thorough explanation of lecanemab administration, patients who consent to the treatment would be enrolled. Patients assinged to the treatment arm would receive standard lecanemab treatment (10mg/kg intravenous infusion every two weeks for 18 months) and standard PD care. Patients who do not consent to the administration of lecanemab would receive stadnard care for PD and be monitored their progress without any further intervention.

Inclusion Criteria:

1. Patients diagnosed with Parkinson's disease
2. Amyloid deposition confirmed by FBB PET
3. Mild cognitive impairment or early dementia (CDR 0.5 or 1) on neuropsychological tests
4. Adults aged 50-90 years

Exclusion Criteria:

1. Cases in which lecanemab administration is contraindicated (based on recommendations from the Korean Dementia Association)
2. Cases in which neuropathologies other than Parkinson's disease or Alzheimer's disease are suspected as the underlying disease