Researchers in Japan found that although the Alzheimer's drug lecanemab successfully removes amyloid plaques from the brain, it does not restore the brain's waste-clearing system within the first few months of treatment.
The study suggests that by the time symptoms appear, damage to nerve cells and the glymphatic system is already well established, making short-term recovery unlikely.
Lecanemab's Surprising Limits in Alzheimer's Treatment
Researchers at Osaka Metropolitan University in Japan, led by graduate student Tatsushi Oura and Dr. Hiroyuki Tatekawa, reported that lecanemab, a drug designed to clear amyloid plaques from the brain, does not improve the brain's waste removal system in the early stages after treatment.
Their results indicate that the nerves of Alzheimer's disease (AD) patients have already sustained considerable damage, and that this waste-clearing function does not rebound quickly. The findings point to the need for treatments that target several biological problems at the same time.
The Complex Web of Alzheimer's Disease Mechanisms
The researchers' results add another piece to the long and complicated effort to understand how AD develops. Although it is the most widespread neurodegenerative disorder, it remains difficult to treat because many different factors contribute to its progression.
A major driver of nerve cell damage in AD is the accumulation of amyloid-β (Aβ) in the brain. In people without the disease, a network known as the glymphatic system circulates cerebrospinal fluid along the spaces surrounding arteries and into brain tissue. There, this fluid mixes with interstitial fluid to help remove metabolic waste products, including Aβ. The name "glymphatic system" comes from the involvement of glial cells in this process.
In AD, however, Aβ builds up and causes arteries to stiffen. This reduces the movement of fluid between the brain and the cerebrospinal fluid, which disrupts waste removal and leads to a series of harmful changes that produce AD symptoms.
Testing Lecanemab's Effects on Brain Clearance
Lecanemab, which was recently approved as a therapeutic option, is intended to lower Aβ levels. To study its effects, the Osaka Metropolitan University team examined the glymphatic system in patients both before and after lecanemab treatment, using the DTI-ALPS index to measure changes.
They found no meaningful difference in this index when comparing pre-treatment results with measurements taken three months after therapy.
What This Means for Future Alzheimer's Treatments
Based on these observations, the researchers concluded that while anti-amyloid drugs can reduce plaque buildup and slow additional cognitive decline, they may not be able to restore functions already lost. By the time symptoms appear, many patients likely have long-standing neuronal damage and glymphatic impairment that are difficult to reverse. The results emphasize how many interconnected factors drive AD and how few of them can be quickly repaired.
"Even when Aβ is reduced by lecanemab, impairment of the glymphatic system may not recover within the short-term," Oura said. "In the future, we want to look at factors like age, the stage of the disease, and degree of lesions in the white matter to further understand the relationship between changes in the glymphatic system due to lecanemab treatment and the outcome of treatment. This will help understand the best way to administer treatment to patients."
Reference: "Unchanged Early Diffusion Tensor Imaging Along Perivascular Space Index After Amyloid-Targeting Disease-Modifying Therapy in Alzheimer's Disease: A Preliminary Study" by Tatsushi Oura, Hiroyuki Tatekawa, Akitoshi Takeda, Ayako Omori, Natsuko Atsukawa, Shu Matsushita, Daisuke Horiuchi, Hirotaka Takita, Taro Shimono, Daiju Ueda, Yoshiaki Itoh and Yukio Miki, 8 September 2025, Journal of Magnetic Resonance Imaging.
DOI: 10.1002/jmri.70118
The study was published in Journal of Magnetic Resonance Imaging.
News
New study suggests a way to rejuvenate the immune system
Stimulating the liver to produce some of the signals of the thymus can reverse age-related declines in T-cell populations and enhance response to vaccination. As people age, their immune system function declines. T cell [...]
Nerve Damage Can Disrupt Immunity Across the Entire Body
A single nerve injury can quietly reshape the immune system across the entire body. Preclinical research from McGill University suggests that nerve injuries may lead to long-lasting changes in the immune system, and these [...]
Fake Science Is Growing Faster Than Legitimate Research, New Study Warns
New research reveals organized networks linking paper mills, intermediaries, and compromised academic journals Organized scientific fraud is becoming increasingly common, ranging from fabricated research to the buying and selling of authorship and citations, according [...]
Scientists Unlock a New Way to Hear the Brain’s Hidden Language
Scientists can finally hear the brain’s quietest messages—unlocking the hidden code behind how neurons think, decide, and remember. Scientists have created a new protein that can capture the incoming chemical signals received by brain [...]
Does being infected or vaccinated first influence COVID-19 immunity?
A new study analyzing the immune response to COVID-19 in a Catalan cohort of health workers sheds light on an important question: does it matter whether a person was first infected or first vaccinated? [...]
We May Never Know if AI Is Conscious, Says Cambridge Philosopher
As claims about conscious AI grow louder, a Cambridge philosopher argues that we lack the evidence to know whether machines can truly be conscious, let alone morally significant. A philosopher at the University of [...]
AI Helped Scientists Stop a Virus With One Tiny Change
Using AI, researchers identified one tiny molecular interaction that viruses need to infect cells. Disrupting it stopped the virus before infection could begin. Washington State University scientists have uncovered a method to interfere with a key [...]
Deadly Hospital Fungus May Finally Have a Weakness
A deadly, drug-resistant hospital fungus may finally have a weakness—and scientists think they’ve found it. Researchers have identified a genetic process that could open the door to new treatments for a dangerous fungal infection [...]
Fever-Proof Bird Flu Variant Could Fuel the Next Pandemic
Bird flu viruses present a significant risk to humans because they can continue replicating at temperatures higher than a typical fever. Fever is one of the body’s main tools for slowing or stopping viral [...]
What could the future of nanoscience look like?
Society has a lot to thank for nanoscience. From improved health monitoring to reducing the size of electronics, scientists’ ability to delve deeper and better understand chemistry at the nanoscale has opened up numerous [...]
Scientists Melt Cancer’s Hidden “Power Hubs” and Stop Tumor Growth
Researchers discovered that in a rare kidney cancer, RNA builds droplet-like hubs that act as growth control centers inside tumor cells. By engineering a molecular switch to dissolve these hubs, they were able to halt cancer [...]
Platelet-inspired nanoparticles could improve treatment of inflammatory diseases
Scientists have developed platelet-inspired nanoparticles that deliver anti-inflammatory drugs directly to brain-computer interface implants, doubling their effectiveness. Scientists have found a way to improve the performance of brain-computer interface (BCI) electrodes by delivering anti-inflammatory drugs directly [...]
After 150 years, a new chapter in cancer therapy is finally beginning
For decades, researchers have been looking for ways to destroy cancer cells in a targeted manner without further weakening the body. But for many patients whose immune system is severely impaired by chemotherapy or radiation, [...]
Older chemical libraries show promise for fighting resistant strains of COVID-19 virus
SARS‑CoV‑2, the virus that causes COVID-19, continues to mutate, with some newer strains becoming less responsive to current antiviral treatments like Paxlovid. Now, University of California San Diego scientists and an international team of [...]
Lower doses of immunotherapy for skin cancer give better results, study suggests
According to a new study, lower doses of approved immunotherapy for malignant melanoma can give better results against tumors, while reducing side effects. This is reported by researchers at Karolinska Institutet in the Journal of the National [...]
Researchers highlight five pathways through which microplastics can harm the brain
Microplastics could be fueling neurodegenerative diseases like Alzheimer's and Parkinson's, with a new study highlighting five ways microplastics can trigger inflammation and damage in the brain. More than 57 million people live with dementia, [...]
