Prothena disclosed Phase 1 data for its amyloid-targeting antibody PRX012, revealing higher incidences of amyloid-related imaging abnormalities with edema (ARIA-E) relative to approved Alzheimer’s disease therapies. This safety signal complicates the therapeutic’s competitive positioning in early symptomatic patients, dampening prospects for approval and potential market share. The findings underscore ongoing challenges in developing safe, efficacious disease-modifying agents targeting amyloid pathology for neurodegenerative disorders.