Safety and Efficacy Study of Gantenerumab in Participants With Early Alzheimer's Disease (AD)

This randomized, double-blind, placebo-controlled, parallel group study will evaluate the efficacy and safety of gantenerumab versus placebo in participants with early (prodromal to mild) AD. All participants must show evidence of beta-amyloid pathology. Eligible participants will be randomized 1:1 to receive either subcutaneous (SC) injection of gantenerumab or placebo. The primary efficacy assessment will be performed at the end of the double blind period at week 116. Participants will then be offered to enter into an open-label extension (OLE). Participants not willing to go to the OLE will participate in a long term follow-up period for up to 50 weeks after the last gantenerumab dose.