A Study of Gantenerumab in Participants With Mild Alzheimer Disease

Inclusion Criteria:

- Clinical diagnosis of probable mild Alzheimer disease (AD) based on National Institute
of Neurological and Communicative Disorders and Stroke/Alzheimer's Disease and Related
Disorders Association (NINCDS/ADRDA) criteria or major NCD based whether or not
receiving AD approved medication

- Cerebral spinal fluid (CSF) result consistent with the presence of amyloid pathology

- Availability of a person ('caregiver') who in the investigator's judgment has frequent
and sufficient contact with the participant, and is able to provide accurate
information regarding the participant's cognitive and functional abilities

- Fluency in the language of the tests used at the study site

- Willingness and ability to complete all aspects of the study

- Adequate visual and auditory acuity, in the investigator's judgment, sufficient to
perform the neuropsychological testing (eye glasses and hearing aids are permitted)

- If currently receiving approved medications for AD, the dosing regimen must have been
stable for 3 months prior to screening

- Agreement not to participate in other research studies for the duration of this trial
and its associated substudies

PART 2 - All participants who have been randomized and are actively participating in the
study are eligible for Part 2

Exclusion Criteria:

- Dementia or neurocognitive disorder (NCD) due to a condition other than AD, including,
but not limited to, frontotemporal dementia, Parkinson disease, dementia with Lewy
bodies, Huntington disease, or vascular dementia

- History or presence of clinically evident vascular disease potentially affecting the
brain that in the opinion of the investigator has the potential to affect cognitive
function

- History or presence of stroke within the past 2 years or documented history of
transient ischemic attack within the last 12 months

- History or presence of systemic autoimmune disorders potentially causing progressive
neurologic disease with associated cognitive deficits

- History of schizophrenia, schizoaffective disorder, or bipolar disorder

- Alcohol and/or substance use disorder (according to the DSM-5) within the past 2 years
(nicotine use is allowed)

- History or presence of atrial fibrillation

- Within the last 2 years, unstable or clinically significant cardiovascular disease
(e.g., myocardial infarction, angina pectoris, cardiac failure New York Heart
Association Class II or higher)

- Uncontrolled hypertension

- Chronic kidney disease

- Impaired hepatic function

PET imaging substudy, in addition to above:

- Prior participation in other research study or clinical care within the last year such
that the total radiation exposure would exceed the local or national annual limits

Part 2 Participants who have been discontinued from the study