SAN FRANCISCO—An experimental Alzheimer’s drug from Eisai and Biogen slowed cognitive decline in a closely watched trial but may carry a risk of serious side effects for certain patients, according to detailed data presented on Tuesday.
The drug, lecanemab, was associated with a dangerous type of brain swelling in nearly 13 percent of patients in the trial that spanned 18 months and enrolled nearly 1,800 participants with early-stage Alzheimer’s.
Some patients also experienced bleeding in the brain, with five suffering macrohemorrhages and 14 percent suffering microhemorrhages— a symptom linked to two deaths of people receiving the drug in a follow-on study.
The companies said in September that lecanemab—an antibody designed to remove sticky deposits of a protein called amyloid beta— reduced the rate of cognitive decline on a clinical dementia scale (CDR-SB) by 27 percent compared to a placebo….