Neuropathological autopsy findings in an individual with Alzheimer’s disease who received long‐term treatment with lecanemab (BAN2401)

Abstract

AbstractBackgroundAnti‐amyloid antibodies administered to patients with Alzheimer’s disease can result in marked reduction of brain amyloid as measured by neuroimaging with amyloid PET ligands. However, there is a lack of pathological data. Here we present neuropathological findings in a patient who received ∼173 weeks of (interrupted) treatment with lecanemab (BAN2401), a humanized IgG1 monoclonal antibody that preferentially targets soluble aggregated β‐amyloid species (protofibrils) and insoluble fibrils, in a Phase 2 study (NCT01767311, Alz Res Therapy 2021;13:80).MethodBrain autopsy was performed on an ∼85 year old whose lecanemab treatment history over 6 years was: 79 weeks 10mg/kg monthly in the double‐blind (DB) phase, then 98 weeks without treatment, then 94 weeks at 10mg/kg biweekly in the open‐label extension (OLE) phase, followed by ∼12 weeks of treatment discontinuation prior to death.ResultClinically, memory symptoms started age ∼77. Study entry was at age ∼80, with mild dementia, CDR 0.5, CDR‐SB 3, and MMSE 24. Florbetapir PET scan was positive at baseline, and negative after 53 weeks DB treatment and at start of OLE. These findings and clinical measures are shown in Table 1. ARIA was not observed during the study. Autopsy showed low brain weight (1052g) with diffuse atrophy, including hippocampi, consistent with atrophy seen on clinical MRI scans. Microscopic findings showed tau pathology including tangles and threads (by AT8 antibody and Bielschowsky staining) throughout neocortex (Braak NF stage VI; B3). Beta‐amyloid immunohistochemical stain (6E10) showed only modest amyloid load (Thal phase 2; A1), with near‐absence of diffuse amyloid deposits and only scattered clusters of neuritic plaques (CERAD stage B; C2).ConclusionIn this autopsy of an individual with Alzheimer’s disease treated with lecanemab, neuropathological changes showed tau and β‐amyloid deposits. However, the pattern of significant tau pathology, accompanied by only a mild degree of β‐amyloid deposits, (A1B3C2), is uncommon in typical (untreated) Alzheimer’s disease. For example, in the NACC neuropathology dataset, only 2% of brains with Braak B2 or B3 show Thal stage A0 or A1. This pattern suggests that lecanemab treatment resulted in a reduction in brain amyloid, consistent with the amyloid PET scanning results in this patient.