Lecanemab is an FDA-approved antibody for the treatment of early stages of Alzheimer's disease that reduces the accumulation of amyloid-beta (Aβ) in the brain.[1] It specifically targets Aβ protofibrils, which are considered the most neurotoxic forms.[1][2][4] The researchers discovered that lecanemab works by activating the brain's immune cells through the Fc fragment of the antibody. This Fc fragment stimulates microglia to remove harmful amyloid plaques. Administered in bimonthly infusions, studies have shown that it slows cognitive and functional decline in patients with early Alzheimer's.[1] In addition, Lecanemab blocks the activation of the contact system by Aβ protofibrils, which reduces the formation of bradykinin and the risk of ARIA.[1] These findings may influence the design of future therapies.