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

Inclusion Criteria:

• Completed Study WN29922 or WN39658, either its double-blind part or OLE part, and didnot discontinue study drug early
• The participant should be capable of completing assessments either alone or with thehelp of the caregiver
• Availability of a person (referred to as the "caregiver")
• For women of childbearing potential: agreement to remain abstinent (refrain fromheterosexual intercourse) or use contraception methods with a failure rate of <1% peryear (bilateral tubal ligation, male sterilization, hormonal contraceptives thatinhibit ovulation, hormone-releasing intrauterine devices, and copper intrauterinedevices) during the treatment period and for at least 16 weeks after the final dose ofgantenerumab
• Agreement not to donate blood or blood products for transfusion for the duration ofthe study and for 1 year after final dose of study drug

Exclusion Criteria:

• Pregnant or breastfeeding, or intending to become pregnant during the study or withinat least 16 weeks after the final dose of study drug
• Prematurely discontinued from Study WN29922 or WN39658
• Any medical condition that may jeopardize the participant's safety if he or shecontinues to receive study treatment
• Received any investigational treatment other than gantenerumab during or sincecompletion of Study WN29922 or WN39658, either its double-blind or OLE part
• Evidence of disseminated leptomeningeal hemosiderosis
• Evidence of intracerebral macrohemorrhage
• Use of prohibited medication
• Evidence of ARIA-E on the last MRI scan report in Study WN29922 or WN39658, either itsdouble-blind or OLE part