A Phase II, Multicenter, Randomized, Double-Blind, Placebo-Controlled, Parallel-Group, Efficacy, and Safety Study of MTAU9937A in Patients With Prodromal to Mild Alzheimer's Disease

Change From Baseline on the CDR-SB

Time Frame: Baseline and 73 Weeks

The Clinical Dementia Rating-Sum of Boxes (CDR-SB) rates impairment in 6 categories (memory, orientation, judgement and problem solving, community affairs, home and hobbies and personal care) on a 5-point scale in which no impairment = 0, questionable impairment = 0.5 and mild, moderate and severe impairment = 1, 2 and 3 respectively. The score range is from 0 to 18 with a high score indicating a high disease severity. The difference in mean change from Baseline to Week 73 between Semorinemab doses and Placebo treated participants was estimated. The difference in mean change from Baseline to Week 73 between Semorinemab doses and Placebo treated participants was estimated.

Other Abnormal MRI Findings

Time Frame: Baseline, Week 9, Week 49, Week 73, Study Treatment Discontinuation, and Week 89

Other abnormal MRI findings by visit. For the Double Blind Period, baseline is defined as last results prior to initiation of study drug. For the Open Label Extension Period, baseline is defined as last results prior to entering the open label period.

Percentage of Participants With Adverse Events

Time Frame: Up to the data cutoff date 15 January 2021 (up to approximately 39 months)

Percentage of participants with at least one adverse event

Change From Baseline on the C-SSRS

Time Frame: Baseline to data cutoff date 15 January 2021 (up to approximately 39 months)

Categories are as defined in the Classification Algorithm for Suicide Assessment (CASA) based on the Columbia Suicide Severity Rating Scale (C-SSRS) questionnaire. SI1: Passive category is "Wish to be dead", SI2: Active-Nonspecific (no method, intent or plan), SI3: Active-Method, but no intent or Plan, SI4: Active-Method and intent, but no plan in C-SSRS. The worst post-baseline suicidal ideation is the highest across post-baseline visits, with highest as SI5 and lowest as SI1. Percentages are based on the total number of subjects in a treatment group. Baseline is the last observation prior to initiation of study drug.