This is a trial designed to assess the ongoing safety of subjects with agitation associated with dementia of the Alzheimer's type after completing a 12-week double-blind trial of brexpiprazole or placebo; drug and placebo are discontinued prior to subjects enrolling in the safety follow-up trial. The trial consists of a continuous 2 month observation period. The trial population will include male and female subjects with a diagnosis of probable Alzheimer's disease.