Antibody fragment prevents hemorrhages associated with new Alzheimer's treatments

Article excerpt

Two newly approved Alzheimer's drugs, lecanemab and donanemab, work by targeting amyloid-beta protein in the brain, but they carry a serious side effect: brain hemorrhages. Researchers have now identified an antibody fragment that prevents these bleeds in mice while preserving the drugs' therapeutic benefits. The finding could make these immunotherapies safer for patients, addressing a critical barrier to their wider use. Both medications were approved by European regulators in 2025 and represent a significant shift in Alzheimer's treatment, though their hemorrhage risk has limited adoption.