A photo shows Lecanemab, sold under the brand name Leqembi, at a hospital in Itabashi Ward, Tokyo on December 25, 2023. Lecanemab is a monoclonal antibody medication used for the treatment of Alzheimer's disease. The drug was developed by Eisai and Biogen and subsequently approved in the United States and Japan.( The Yomiuri Shimbun via AP Images )