The present invention provides methods of monitoring Aβ-directed immunotherapy. The methods involve administering a PET ligand that binds to amyloid deposits and detecting the PET ligand in the brain to provide an indication of the level and/or distribution of amyloid deposits. Surprisingly, the data in the present application show that a statistically significant reduction in amyloid deposits occurs early and consistently among patients following initiation of treatment before statistically significant effects of most if not all other markers are detectable. In consequence, the present methods allow early detection of whether a patient is responding to the Aβ-directed immunotherapy and if necessary adjustment of the immunotherapy regime.
