Multiple Dose Study of Aducanumab (BIIB037) (Recombinant, Fully Human Anti-Aβ IgG1 mAb) in Participants With Prodromal or Mild Alzheimer's Disease

The study consists of a placebo-controlled period to study week 54, followed by a long-term extension to study week 518. The placebo-controlled period is conducted with a staggered, parallel group design, with the first 3 treatment arms conducted in parallel, 2 further treatment arms subsequently beginning in parallel, 2 additional treatment arms beginning in parallel, and the last 2 treatment arms subsequently beginning in parallel. Qualifying participants can enter the long-term extension period for up to 42 additional doses of active drug for the first 3 years of LTE. Furthermore, up until the last participant in Arms 8 and 9 has had his or her last dose in the fifth year of the LTE, eligible participants will be able to continue treatment beyond the third year of the LTE.