This study will be conducted in subjects with early AD, including subjects with mild cognitive impairment (MCI) due to AD and a subset of mild AD.
The purpose of this study is to find out whether (study drug) has the potential to be a helpful treatment that slows down disease progression in subjects with early Alzheimer?s Disease (AD) by comparing it to placebo and to evaluate its safety (side effects), and to find out more about aducanumab.
The subject will have the option of participating in four sub-studies: DNA, positron emission tomography (PET), magnetic resonance imaging (MRI), cerebrospinal fluid (CSF) or the Long Term Extension study (LTE).
Study duration for each subject participating in the placebo-controlled period only will be approximately 102 weeks (up to an 8 week Screening Period, 76 weeks of placebo or aducanumab dosing, and 18 weeks of follow-up).
For subjects who enter the optional LTE, the total duration will be approximately 206 weeks or 47 months (up to an 8 week Screening Period, 76 weeks of placebo or aducanumab dosing, 4 weeks of follow-up, 100 weeks of dose-blind aducanumab dosing, and 18 weeks of follow-up).