The primary objective of this study is to evaluate the safety and tolerability of single doses of BIIB061 administered to healthy adult volunteers. Secondary objectives in this study population are to determine the single-dose pharmacokinetic (PK) profile and the absolute bioavailability (Fabs) of BIIB061 and to determine the effects of food intake (high-fat, high-calorie meal) on BIIB061 PK and safety.

Key Inclusion Criteria:

• Males and postmenopausal (defined as no menses for 12 months and confirmed by follicle-stimulating hormone (FSH) levels determined at screening to be in the postmenopausal range) or surgically sterile females.
• All males must practice effective contraception during the study and be willing and able to continue male contraception for 3 months after the dose of study treatment. All male participants must also be willing to refrain from sperm donation for at least 3 months after their last dose of study treatment. Note: Females of childbearing potential, are not allowed to enter the study.
• Must be in good health and have normal vital signs as determined by the Investigator.
• Participants agree to abstain from alcohol ingestion for the duration of time that they are in the study.
• Must be a nonsmoker and must not use chewing tobacco or nicotine products, for at least 3 months prior to Day -1.
• Must have a body mass index (BMI) of 18 to 30 kg/m2, inclusive.

Key Exclusion Criteria:

• History of or positive test result at screening for human immunodeficiency virus (HIV).
• History of any clinically significant cardiac, endocrinologic, hematologic, hepatic, immunologic, metabolic, urologic, pulmonary, neurologic, dermatologic, psychiatric, renal, oncologic, or other major disease, as determined by the Investigator.
• Clinically significant (as determined by the Investigator) 12-lead electrocardiogram (ECG) abnormalities, including corrected QT interval using Fridericia's correction method of >450 ms for males and >470 ms for females.
• History of severe allergic or anaphylactic reactions.
• Serious infection (e.g., pneumonia, septicemia) as determined by the Investigator, within 3 months prior to Day -1.
• Consumption of grapefruit or grapefruit-containing products within 3 days of dosing.
• Treatment with any over-the-counter products, including herbal and/or alternative health preparations and procedures within the 14 days prior to Day -1.
• Current enrollment in any other drug, biologic, device, or clinical study, or treatment with an investigational drug or approved therapy for investigational use within 30 days (or 5 half-lives, whichever is longer) prior to Day -1.
• Blood donation (1 unit or more) within 30 days prior to Day -1
• History of drug or alcohol abuse (as determined by the Investigator), a positive urine drug/alcohol test, or a positive cotinine test at Screening or Day -1, or alcohol use within 48 hours (as reported by the subject) prior to Day -1.
• Vigorous exercise (as determined by the Investigator) within 48 hours prior to Day -1.
• History of malignant disease, including solid tumors and hematologic malignancies.
• Surgery within 3 months prior to Day-1.
• History of seizures other than childhood febrile seizure.
• Inability or unwillingness to comply with study requirements.

NOTE: Other protocol-defined inclusion/exclusion criteria may apply