Japanese Study Reveals Shortcomings of Alzheimer’s Drug Lecanemab

Research from Osaka Metropolitan University in Japan indicates that while the amyloid-clearing drug lecanemab can reduce amyloid plaques associated with Alzheimer’s disease, it does not enhance the brain’s waste clearance system in the short term. This finding, released on November 11, 2025, suggests that clearing amyloid alone may not be sufficient to reverse the neural damage that characterizes Alzheimer’s.

The study, conducted by graduate student Tatsushi Oura and Dr. Hiroyuki Tatekawa, focused on the glymphatic system, which plays a crucial role in clearing metabolic waste from the brain. Their research highlights the complexity of Alzheimer’s disease, emphasizing the need for treatments that address multiple biological pathways.

Understanding the Glymphatic System and Alzheimer’s

Alzheimer’s disease is primarily marked by the accumulation of the protein amyloid-β (Aβ), which disrupts the brain’s natural waste management processes. In healthy individuals, the glymphatic system circulates cerebrospinal fluid, facilitating the removal of waste products, including Aβ. However, in patients with Alzheimer’s, the buildup of Aβ leads to stiffening of arteries, which hinders fluid flow and impairs waste clearance.

The research team employed a specialized imaging technology known as the DTI-ALPS index to assess the glymphatic system in patients both prior to and three months after receiving lecanemab treatment. Contrary to expectations, they found no significant improvement in the glymphatic system post-treatment.

Implications of the Findings

The absence of short-term improvement in the glymphatic function raises significant questions about the efficacy of treatments solely aimed at amyloid reduction. The researchers concluded that while lecanemab can lower plaque levels and potentially slow cognitive decline, it does not suffice to restore lost brain function. By the time Alzheimer’s symptoms manifest, both neuronal damage and impairments in waste clearance are likely well established and resistant to reversal.

Oura remarked, “Even when Aβ is reduced by lecanemab, impairment of the glymphatic system may not recover within the short-term.” He emphasized the necessity of exploring various factors, including patient age, disease stage, and extent of white matter lesions, to better understand the relationship between glymphatic system changes and treatment outcomes.

These findings point to a pressing need for a multifaceted approach to Alzheimer’s treatment. Addressing only amyloid plaques may overlook other critical aspects of the disease’s progression and impact on brain function.

The study has been published in the Journal of Magnetic Resonance Imaging, contributing to the growing body of evidence that Alzheimer’s is a multifactorial disorder that requires comprehensive treatment strategies. As researchers continue to investigate, the urgency of developing therapies that can simultaneously target multiple biological pathways becomes increasingly clear.