The primary objectives of this study are to evaluate the absolute bioavailability of a single, fixed sub-cutaneous (SC) dose of aducanumab compared with a single, weight-based intra-venous (IV) dose in healthy participants and to characterize the pharmacokinetics (PK) profile of aducanumab. The secondary objectives are to evaluate the safety and tolerability of aducanumab administered via SC and IV routes in healthy participants and to characterize additional PK parameters of a single, fixed SC dose of aducanumab and a weight-based IV dose in healthy participants.

Key Inclusion Criteria:

• A minimum weight of 45 kg, inclusive, at Day -1.
• All women of childbearing potential and all men must practice highly effective contraception during the study and be willing and able to continue contraception for 24 weeks after study treatment dosing (Day 1).
• Must be in good health (as determined by the Investigator) based on the medical history and screening evaluations.

Key Exclusion Criteria:

• Mini mental state examination (MMSE) score of <27 at Screening.
• History of any clinically significant cardiac, endocrinologic, hematologic, hepatic, gastrointestinal, immunologic, metabolic, urologic, pulmonary, neurologic, dermatologic, psychiatric, or renal disease, or other major disease, as determined by the Investigator.
• History of severe allergic or anaphylactic reactions that in the opinion of the Investigator is likely to be exacerbated by any component of the study treatment.
• History of malignant disease, including solid tumors and hematologic malignancies (with the exception of basal cell and squamous cell carcinomas of the skin that have been completely excised prior to study entry).
• History of, or positive test result at Screening for, human immunodeficiency virus (HIV).
• Positive test result at Screening for hepatitis C virus antibody (HCVAb).
• Positive test result at Screening for hepatitis B virus (defined as positive for both, hepatitis B surface antigen [HBsAg] AND hepatitis B core antibody [HBcAb]).
• Chronic, recurrent, or serious infection (e.g., pneumonia, septicemia) as determined by the Investigator, within 90 days prior to Day -1.

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply