Safer Alzheimer’s Treatment: Antibody Fragments Reduce Brain Hemorrhage Risk
Researchers at the Universitat Autònoma de Barcelona (UAB) have demonstrated in mice that using an antibody fragment could safely prevent brain hemorrhages associated with new Alzheimer’s treatments. According to a university statement, this fragment maintains therapeutic effects while avoiding the recruitment of systemic immune cells into the brain.
The European Medicines Agency approved two immunotherapy-based antibodies for Alzheimer’s in 2025: lecanemab (‘Leqembi’ by Biogen) and donanemab (‘Kisunla’ by Eli Lilly and Company). These laboratory-obtained antibodies target the beta-amyloid peptide, a protein fragment that accumulates in the brains of Alzheimer’s patients. According to Europa Press, removing this peptide helps slow the cognitive decline typical of the disease.
Why are some Alzheimer’s treatments linked to brain hemorrhages?
The Protein Design and Immunotherapy group at UAB, led by Sandra Villegas, has operated on the hypothesis that full antibodies may be unsafe for treating neurodegenerative diseases. Villegas states that full antibodies can drag systemic immune cells into the brain.
This recruitment of immune cells is linked to the development of hemorrhages. To address this, the research team developed a single-chain antibody fragment known as scFv-h3D6. This fragment targets the beta-amyloid peptide but lacks the specific region responsible for recruiting those systemic immune cells.
How does the new antibody fragment work?
The UAB team tested the scFv-h3D6 fragment across molecular, cellular, and cognitive scales in mice. They used magnetic resonance imaging (MRI) to compare the effects of the fragment against a full antibody called bapineuzumab, from which the fragment was derived.
MRI results showed a notable difference. Hemorrhages appeared when the full bapineuzumab antibody was administered, but these hemorrhages did not appear when only the antibody fragment was used. According to the university, the therapeutic effects remained intact despite the absence of the full antibody structure.
What could happen next for Alzheimer’s research?
The success of the scFv-h3D6 fragment in mice suggests that antibody fragments could be a viable path for human treatment. A possible next step may involve further testing to determine if these results translate to human patients.
If the safety profile holds, this approach could lead to a new generation of immunotherapy that reduces the risk of brain bleeding. Researchers may continue to refine these fragments to optimize how they interact with beta-amyloid peptides in the brain.
Frequently Asked Questions
What is the target of these Alzheimer’s treatments?
They target the beta-amyloid peptide, a protein fragment that accumulates in the brains of patients and contributes to cognitive decline.
Who led the research at the Universitat Autònoma de Barcelona?
The Protein Design and Immunotherapy group was led by Sandra Villegas.
How did researchers verify that the fragment prevented hemorrhages?
The team used magnetic resonance imaging (MRI) to visualize the brain and compare the effects of the antibody fragment against the full bapineuzumab antibody.
Do you think the reduction of side effects is the most critical factor in the adoption of new Alzheimer’s therapies?