Screening amyloid PET scan was considered baseline evaluation.Brain amyloid load was quantified in terms of Standardized Uptake Value Ratio (SUVR),defined as ratio of tracer uptake in cortical composite target region of interest(ROI)to tracer uptake in reference ROI.Composite region: frontal,parietal,temporal,posterior cingulate cortex,anterior cingulate cortex. Reference ROI (whole cerebellum) was represented by weighted average of Cerebellum Ventral,Cerebellum Dorsal (left/right), Cerebellar White Matter.SUVR linearly transformed to standardized Centiloid Scale (CL) using formula CL=175.6xSUVR-174.2.CL ranges from <0 to >100, anchor points are 0=high-certainty amyloid negative scan and 100=amount of global amyloid deposition found in typical AD scan.

ITT population set, included all enrolled participants (i.e., who gave informed consent, did not fail screening, and had at least one Amyloid PET scan with a valid quantitative measurement performed with either florbetaben or flutemetamol), whether or not the participant received the assigned treatment. Number analyzed is the number of participants with data available for analysis at the specified timepoint.

HAQ comprised 4 items completed by study partner capturing confidence (Q1), convenience (Q2), ease of use (Q3), and overall satisfaction (Q4) with administering medication. Response options Q1: Not at all confident, somewhat confident, confident, very confident; Q2: Not at all convenient, somewhat convenient, convenient, very convenient; Q3: Not at all easy, somewhat easy, easy, very easy; Q4:Not at all satisfied, somewhat satisfied, satisfied, very satisfied.

Opportunity for Home Dosing Safety-Evaluable Analysis Set (OH-SE) included all participants of the SE analysis set who did not discontinue the study drug before week 26. Number analyzed is the number of participants with data available for analysis at the specified timepoint.

AE: any untoward medical occurrence in participant administered pharmaceutical product, which does not necessarily have a causal relationship with treatment. Also, any unfavorable, unintended sign, symptom, or disease temporally associated with use of medicinal product, whether or not considered related to it. SAE: any AE that was fatal, life threatening, required prolonged inpatient hospitalization, resulted in significant disability or resulted in a congenital anomaly to mother exposed to study treatment. This was a single-arm study and all participants received gantenerumab according to predefined universal up-titration scheme as follows: 120 mg Q4W (Day 1, Week (W) 4, and W8), then 255 mg Q4W (W 12, 16, and 20), then 255 mg Q2W for 12 weeks (W 24, 26, 28, 30, 32, and 34), followed by target dose of 255 mg Q1W (W 36 to 104). Data was collected and reported in single arm for each participant who started treatment as specified and either completed or discontinued study.

Safety Evaluable population included all participants enrolled who received at least one dose of study treatment, whether prematurely withdrawn from the study or not.

C-SSRS=assessment tool used to assess lifetime suicidality of a participant (at baseline) as well as any new instances of suicidality (C-SSRS since last visit). Structured interview prompts recollection of suicidal ideation, including intensity of ideation, behavior, & attempts with actual/potential lethality. Categories have binary responses (yes/no) & include Wish to be Dead; Non-specific Active Suicidal Thoughts; Active Suicidal Ideation with Any Methods(Not Plan)without Intent to Act; Active Suicidal Ideation with Some Intent to Act, without Specific Plan; Active Suicidal Ideation with Specific Plan and Intent, Preparatory Acts and Behavior; Aborted Attempt; Interrupted Attempt; Actual Attempt (non-fatal);Completed Suicide. Suicidal ideation/behavior is indicated by a "yes" answer to any of the listed categories. Score of 0 is assigned if no suicide risk is present. Score of 1 or higher= suicidal ideation or behavior. Categories with non-zero values are only reported here.

Safety Evaluable population included all participants enrolled who received at least one dose of study treatment, whether prematurely withdrawn from the study or not. Overall number analyzed is the number of participants with data available for analysis.

ARIA are an identified risk with anti-amyloid antibodies, including gantenerumab. These changes can be identified on brain MRI. The occurrences of imaging abnormalities in vasogenic edema and sulcal effusions (ARIA-E) were evaluated.

MRI Safety-Evaluable Analysis Set included all participants of the SE analysis set who had at least one post-baseline MRI assessment.

ARIA are an identified risk with anti-amyloid antibodies, including gantenerumab. These changes can be identified on brain MRI. ARIA-H (H for hemosiderosis) are small foci of signal loss observed on MRI sequences sensitive for paramagnetic tissue properties and comprise cerebral microbleeds (small foci of bleeding in the brain parenchyma) and leptomeningeal hemosiderosis (small foci of bleeding on the surface of the brain). These changes also occur sporadically in AD.

MRI Safety-Evaluable Analysis Set included all participants of the SE analysis set who had at least one post-baseline MRI assessment.

An AE is any unfavorable and unintended sign, symptom, or disease temporally associated with the use of an investigational product or other protocol-imposed intervention, regardless of attribution. Injection reactions (local and systemic) were defined as AEs that occured during or within 24 hours after study drug administration that were judged to be related to the study drug injection.

Safety Evaluable population included all participants enrolled who received at least one dose of study treatment, whether prematurely withdrawn from the study or not.

A participant with an ADA assay result from at least one post-baseline sample was defined as a post-baseline evaluable participant. Treatment Emergent ADA was defined as a participant with a negative or missing baseline ADA result(s) and at least one positive post-baseline ADA result, or a participant with a positive ADA result at baseline who has at least one post-baseline titer results with at least a >2.5-fold increase in titer compared to baseline greater than the baseline titer result.

Safety Evaluable population included all participants enrolled who received at least one dose of study treatment, whether prematurely withdrawn from the study or not. Overall number analyzed is the number of participants with an ADA assay result from at least one post-baseline sample.

PK evaluable population included only participants that received the previous 6, 4, 6 or 6 planned doses at weeks 24, 36, 52 and 76, respectively. Overall number analyzed was the number of participants with data available for analysis. Number Analyzed was the number of participants with data available for analyses at the specified timepoint.

The change from baseline at Week 52 using the once-weekly dosing frequency was analysed using the centiloid scale. The centiloid scale anchor points are 0 and 100, where 0 represents a high-certainty amyloid negative scan and 100 represents the amount of global amyloid deposition found in a typical AD scan. The range of centiloid values can be below 0 (negative) and greater than 100.

ITT population set, included all enrolled participants (i.e., who gave informed consent, did not fail screening, and had at least one Amyloid PET scan with a valid quantitative measurement performed with either florbetaben or flutemetamol), whether or not the participant received the assigned treatment. Overall number analyzed is the number of participants with data available for analysis.