Single Ascending Dose Study of the Safety, Tolerability, and Pharmacokinetics of BIIB061 in Healthy Adult Volunteers Including Absolute Bioavailability and Food Effect

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