Summary: Researchers report that lecanemab—the anti-amyloid drug designed to clear amyloid-β plaques—did not restore the brain’s glymphatic waste-clearance function within three months. Using MRI-based DTI-ALPS imaging to evaluate perivascular fluid movement, the study detected no measurable recovery in glymphatic activity shortly after treatment.
The findings suggest that by the time symptoms appear and treatment begins, the neuronal damage and impairment of clearance pathways may already be advanced and not quickly reversible. The results underscore the need for multi-targeted strategies that address more than amyloid reduction alone when treating Alzheimer’s disease.
Key Facts
- Study finding: Lecanemab reduces amyloid-β plaques but did not improve glymphatic waste clearance as measured by the DTI-ALPS index after three months.
- Clinical implication: Short-term amyloid removal may slow progression but may not restore lost clearance and neuronal function once damage is established.
- Research direction: Further investigation will examine longer follow-up, age effects, disease stage, and white matter lesion burden to understand treatment impact over time.
Source: Osaka Metropolitan University
Summary of the study
A research team at Osaka Metropolitan University, led by graduate student Tatsushi Oura and Dr. Hiroyuki Tatekawa, evaluated whether amyloid-targeting therapy with lecanemab would improve glymphatic function in people with Alzheimer’s disease (AD). The glymphatic system normally moves cerebrospinal fluid along perivascular spaces into the brain parenchyma, mixes it with interstitial fluid, and clears metabolic waste including amyloid-β (Aβ). In AD, Aβ accumulation and associated vascular stiffening can impede that flow and impair waste clearance, contributing to neurodegeneration.
The investigators measured the diffusion tensor imaging along perivascular space (DTI-ALPS) index, an MRI-derived surrogate marker proposed to reflect glymphatic activity, before treatment and three months after initiating lecanemab. Although the drug effectively reduced amyloid burden as expected, the DTI-ALPS index showed no significant change over that short interval.
From these observations the authors concluded that while anti-amyloid therapy can lower plaque levels and may slow cognitive decline, it does not necessarily restore impaired clearance mechanisms quickly. This implies that damage to neurons and perivascular clearance pathways may be established well before clinical presentation, limiting short-term reversibility with amyloid removal alone.
“Even when Aβ is reduced by lecanemab, impairment of the glymphatic system may not recover within the short term,” said Tatsushi Oura. The team emphasized the importance of assessing additional factors—such as patient age, disease stage, and the extent of white matter lesions—to better understand how glymphatic changes relate to treatment outcomes and to identify optimal strategies for administering therapies.
Funding and data sources
The study was supported by the Takeda Science Foundation (ROR ID: 02y123g31) and the Japan Society for the Promotion of Science (JSPS) KAKENHI (grant number: 25K19115). Imaging and cohort data were obtained from OASIS-3 (Longitudinal Multimodal Neuroimaging), whose principal investigators include T. Benzinger, D. Marcus, and J. Morris, and which is supported by multiple NIH grants listed in the original report.
Key questions answered
A: Not in the short term. The three-month follow-up in this preliminary study found no measurable recovery in the glymphatic system despite plaque reduction.
A: Clearing amyloid alone may not be sufficient to reverse established neuronal or clearance-pathway damage. Effective treatment may require combined approaches that target multiple disease mechanisms.
A: Future studies will explore longer treatment durations, effects of patient age and disease severity, and the role of white matter lesions to evaluate whether glymphatic function can recover over time or with combination therapies.
About this neuropharmacology and Alzheimer’s disease research news
Author: Matthew Coslett
Source: Osaka Metropolitan University
Contact: Matthew Coslett – Osaka Metropolitan University
Image credit: Neuroscience News
Original research: Open access. Title: “Unchanged Early Diffusion Tensor Imaging Along Perivascular Space Index After Amyloid-Targeting Disease-Modifying Therapy in Alzheimer’s Disease: A Preliminary Study” by Hiroyuki Tatekawa et al., Journal of Magnetic Resonance Imaging.
Abstract (summary)
Alzheimer’s disease (AD) features progressive accumulation of amyloid-β peptides and impaired interstitial waste clearance via the glymphatic system. Newly approved disease-modifying monoclonal antibodies, such as lecanemab, aim to clear Aβ and slow cognitive decline. The diffusion tensor imaging along the perivascular space (DTI-ALPS) index has been proposed as a noninvasive marker associated with glymphatic activity; it typically declines with aging and is lower in AD patients than in cognitively normal individuals. This preliminary study quantified the DTI-ALPS index in AD patients before and three months after initiating amyloid-targeting therapy to provide early reference values for longitudinal assessment of future cohorts treated with disease-modifying agents.