Brain shrinkage observed in patients undergoing treatment with Alzheimer’s drugs like lecanemab and donanemab may not be a cause for concern, according to a new study led by UCL experts. The research suggests that this brain volume loss could be a sign that the drugs are effectively removing toxic amyloid plaques, rather than indicating a harmful side effect. This finding offers a new perspective on the observed brain shrinkage, which had previously raised concerns among some scientists.
The study, which analyzed data from a dozen different trials, found that brain volume loss was only evident in patients treated with drugs that successfully removed amyloid plaques. The degree of brain shrinkage correlated with the drug's effectiveness in removing amyloid, and there was no apparent link between the volume loss and worsened memory or cognitive abilities. Professor Nick Fox, director of the UCL Dementia Research Centre, suggests that this phenomenon should be termed “amyloid-removal-related pseudo-atrophy,” indicating it as an expected outcome of amyloid plaque removal.
Understanding Amyloid Plaques and Brain Volume
The UCL team posits that amyloid plaques occupy a volume greater than the amyloid beta protein itself, as they contain other components. Therefore, the removal of these plaques could lead to a noticeable decrease in brain volume. While a previous analysis in Neurology had warned that these drugs might compromise long-term brain health by accelerating brain atrophy, the new findings suggest a more nuanced interpretation.
Expert Perspectives and Future Research
David Thomas, head of policy and public affairs at Alzheimer’s Research UK, emphasized the need for further investigation to fully understand how these treatments affect the brain. He stated that longer-term studies are needed to track brain volume changes during and after treatment, alongside monitoring cognitive function and side effects.
Clinical Significance and Treatment Landscape
Lecanemab, one of the drugs in question, has been shown in trials to slow cognitive decline by approximately five months. It received a license for use in the UK after regulatory review of safety data. These drugs represent a significant advancement in Alzheimer’s treatment, offering the potential to slow the progression of the disease. As these therapies become more accessible, continued data collection and analysis will be crucial to refining our understanding of their effects and optimizing their use in clinical practice.
