Scientists Crack How Alzheimer's Drug Clears Brain Plaques

For the first time, scientists know exactly how a breakthrough Alzheimer's drug removes the toxic plaques that steal people's memories.

Researchers at VIB and KU Leuven in Belgium discovered that lecanemab activates the brain's immune cells through a specific antibody fragment called Fc. This fragment works like a switch, telling microglia (the brain's cleanup crew) to start removing the harmful amyloid plaques that cause dementia.

The drug, sold as Leqembi, already has FDA approval and helps slow cognitive decline in Alzheimer's patients. But until now, doctors didn't fully understand why it worked, making it harder to improve the treatment or reduce side effects.

The team used a specially designed mouse model containing human brain immune cells to watch the drug in action. When they removed the Fc fragment, the antibody stopped working completely. The microglia just sat there, unable to clear the plaques.

Dr. Giulia Albertini, who co-led the study, explains that the Fc fragment acts as an anchor. Microglia latch onto it near plaques, which reprograms these cells to clean more efficiently. Without that anchor, nothing happens.

The researchers then looked inside the activated microglia to see what changed. They found specific genes turning on, including one called SPP1, that triggered the cleanup process. These cells started gobbling up plaques through phagocytosis, the same process your immune system uses to eat bacteria.

Why This Inspires

This discovery means future Alzheimer's treatments might skip antibodies entirely and activate microglia directly. That could mean fewer side effects and better results for patients.

More than 55 million people worldwide live with Alzheimer's disease. Current treatments help, but they're not perfect. Understanding exactly how lecanemab works gives scientists a roadmap for designing the next generation of therapies.

The research team used cutting-edge technology called spatial transcriptomics to map gene activity in individual brain cells. This level of detail was impossible just a few years ago. Now it's opening doors to treatments that seemed like science fiction.

Professor Bart De Strooper, who led the research published in Nature Neuroscience, says this knowledge changes everything about how we approach Alzheimer's drug design. Instead of guessing what might work, scientists can now target the exact cellular programs responsible for clearing plaques.

For families watching loved ones fade into dementia, this represents real hope: not just better drugs today, but a clear path to even more effective treatments tomorrow.