A Study to Verify the Clinical Benefit of Aducanumab in Participants With Early Alzheimer's Disease

Change From Baseline in Clinical Dementia Rating Scale - Sum of Boxes (CDR-SB) Score at Week 78

Timeframe: Baseline, Week 78

The Clinical Dementia Rate Scale integrates assessments from 3 domains of cognition (memory, orientation, judgment/problem-solving) and 3 domains of function (community affairs, home/hobbies, personal care). Following the caregiver interview and systematic participant examination, the rater assigns a score describing the participant's current performance level in each of these domains of life functioning. The "Sum of boxes" scoring methodology sums the score for each of the 6 domains and provides a value ranging from 0 to 18. Higher scores indicate greater impairment. A positive change from baseline indicates greater impairment.

Change From Baseline in Integrated Alzheimer's Disease Rating Scale (iADRS) Score at Weeks 78 and 106

Timeframe: Baseline, Weeks 78 and 106

The iADRS composite captures a decline in both cognition and daily function. It is a simple linear combination of the Alzheimer's disease assessment scale, cognitive subscale (ADAS-Cog13), and the Alzheimer's disease cooperative study scale for activities of daily living in mild cognitive impairment (ADCS-ADL-MCI). The ADAS-Cog13 scale ranges from 0 to 85 (higher scores indicate worse performance) and the ADCS-ADL-MCI scale ranges from 0 to 53 (higher scores indicate greater independent, healthy functioning). The total score for iADRS scale ranges from 0 to 138, where higher scores indicate better performance.

Change From Baseline in Alzheimer's Disease Cooperative Study for Activities of Daily Living in Mild Cognitive Impairment (ADCS-ADL-MCI) Scale Score at Weeks 78 and 106

Timeframe: Baseline, Weeks 78 and 106

The ADCS-ADL-MCI scale consists of 17 instrumental items (e.g., shopping, preparing meals, using household appliances, etc) and 1 basic item (getting dressed). Ratings reflect caregiver observations about the participant's actual functioning over the previous month and provide an assessment of change in the functional state of the participant over time. The total score ranges from 0 to 53. Higher scores indicate greater independent, healthy functioning. A positive change from baseline indicates healthy functioning while a negative change from baseline indicates a decline in independent functioning.

Change From Baseline in Alzheimer's Disease Assessment Scale, Cognitive Subscale (ADAS-Cog13) at Weeks 78 and 106

Timeframe: Baseline, Weeks 78 and 106

ADAS-Cog13 comprises both cognitive tasks and clinical ratings of cognitive performance. The cognitive subscale items capture word recall, ability to follow commands, the ability to correctly copy or draw an image, naming, the ability to interact with everyday objects, orientation, word recognition, memory, comprehension of spoken language, word-finding, and language ability, with a measure for delayed word recall and concentration/distractibility. The total score ranges from 0 to 85. Higher scores indicate worse performance. A positive change from baseline indicates decline in cognitive performance.

Change From Baseline in Mini-Mental State Examination (MMSE) Scale Score at Weeks 78 and 106

Timeframe: Baseline, Weeks 78 and 106

The MMSE scale is a performance-based test of global cognitive status. It consists of 11 tasks that assess orientation, word recall, attention and calculation, language abilities, and visuospatial functions. The scores from the 11 tests are combined to obtain the total score, which ranges from 0 to 30. Higher scores indicate better performance. A negative change from baseline indicates decline in cognitive performance.

Change From Baseline in Neuropsychiatric Inventory-10 (NPI-10) Score at Weeks 78 and 106

Timeframe: Baseline, Weeks 78 and 106

The NPI-10 is a questionnaire administered to the informant, designed to obtain information on the presence of neuropsychiatric symptoms and behaviors in a participant with Alzheimer's disease. Ten areas are assessed: delusions, hallucinations, agitation/aggression, depression, anxiety, elation/euphoria, apathy/indifference, disinhibition, irritability and aberrant motor behavior. The NPI total score ranges from 0 to 120. Higher scores indicate greater impairment. A negative change from baseline indicates improvement (symptom reduction).

Change From Baseline in Amyloid Positron Emission Tomography (PET) Signal at Weeks 78 and 104

Timeframe: Baseline, Weeks 78 and 104

Amyloid PET scan assesses cerebral amyloid load using radiotracers which is standardized into centiloids. Centiloid values on centiloid scale is based on mean composite standardized uptake value ratio (SUVR).

Change From Baseline in Tau PET Signal at Weeks 78 and 104

Timeframe: Baseline, Weeks 78 and 104

The cerebral tau level was measured by tau PET imaging. Tau PET imaging was conducted using radiotracer. SUVR is a ratio of PET uptake measured in brain region of interest and a disease-free reference region. A higher SUVR is an indication of increased PET radiotracer uptake and worsening disease.

Change From Baseline in CDR-SB Score at Week 106

Timeframe: Baseline, Week 106

The CDR integrates assessments from 3 domains of cognition (memory, orientation, judgment/problem-solving) and 3 domains of function (community affairs, home/hobbies, personal care). Following caregiver interview and systematic participant examination, the rater assigns a score describing the participant's current performance level in each of these domains of life functioning. The CDR-SB sums the score for each of the 6 domains and provides a value ranging from 0 to 18. Higher scores indicate greater impairment. Positive change from baseline indicates greater impairment.

Change From Baseline in Global Statistical Test (GST) Composite Z-Score at Weeks 78 and 106

Timeframe: Baseline, Weeks 78 and 106

GST z-score is an average of z-scores of CDR-SB, ADASCog13 and ADCS-ADL-MCI. CDR-SB assesses 3 cognitive (memory,orientation, judgment/problem-solving)and 3 functional(community affairs,home/hobbies,personal care) domains. Sum of Boxes method combines scores across 6 domains, ranging from 0-18(higher scores=greater impairment). ADAS-Cog13 evaluates cognitive tasks like word recall, naming, orientation and memory, with scores from 0-85 (higher scores=worse performance). ADCS-ADL-MCI rates 17 tasks (e.g.,shopping, preparing meal) and 1 basic task(dressing) with scores from 0-53 (higher scores=greater independence/healthy functioning). z-score\>0 indicates greater impairment/worse performance for CDR-SB and ADASCog13 scales and improved functioning for ADCS-ADL-MCI. For ADCS-ADL-MCI, z-score were reversed (new reversed value=original value-1) to make interpretation consistent. The GST z-score of 0 indicates population mean and score\>0 indicate greater impairment/worse performance.