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