Amlenetug (Lu AF82422) is a human monoclonal antibody targeting α-synuclein that is in development for multiple system atrophy, demonstrating robust inhibition of α-synuclein seeding induced by diverse fibrillar assemblies in mouse primary neurons and by aggregates derived from MSA brain homogenates, while in vivo studies show that both intracerebral co-injection and peripheral administration effectively suppress α-synuclein seeding and pathological propagation.