A Study to Evaluate the Safety and Tolerability of Long-term Administration of Gantenerumab in Participants With Alzheimer's Disease (AD)

Inclusion Criteria:

• Part 1: Participants who completed the open-label extensions (OLEs) of studies WN25203or WN28745 will be eligible to participate in Part 1 of the study
• Part 2: All participants who have completed Week 104 visit in Part 1 will be eligiblefor Part 2 of the study
• For Part 1 and Part 2:
• For women of childbearing potential: agreement to remain abstinent (refrain fromheterosexual intercourse) or use contraceptive methods that result in a failure rateof <1% per year during the treatment period and for at least 16 weeks after the lastdose of study drug
• Agreement to not donate blood or blood products for transfusion for the duration ofthe study and for 1 year after final dose of study drug
• Availability of a person ('caregiver') who in the investigator's judgement, hasfrequent and sufficient contact with the participant

Exclusion Criteria:

• Prematurely discontinued from the OLEs of studies WN25203 or WN28745 or from studydrug for any reason
• Any medical condition that may jeopardize the participant's safety if he or shecontinues to receive study treatment
• If the participant is unlikely to benefit from gantenerumab therapy, based on diseaseprogression or other factors, or if study participation is otherwise not in theparticipant's best interest
• Any investigational treatment other than gantenerumab during or since completion ofthe OLEs of studies WN25203 or WN28745
• Pregnancy
• Evidence of disseminated leptomeningeal hemosiderosis (i.e., more than three focalleptomeningeal hemosiderosis)
• Evidence of intracerebral macrohemorrhage
• Part 2: Participants who have been discontinued from Part 1 of the study