The primary objective of this study is to evaluate the effect of multiple doses of the UGT inhibitor valproic acid on the single-dose pharmacokinetics of BIIB074. The secondary objectives of this study are to evaluate the safety and tolerability of BIIB074 when administered alone and when coadministered with the UGT inhibitor valproic acid and to evaluate the effect of the UGT inhibitor valproic acid on the PK of the M13, M14, and M16 metabolites of BIIB074.

Key Inclusion Criteria:

• Must have a body mass index between 18 and 32 kg/m^2, inclusive.
• Must be male, postmenopausal female, or surgically sterile female
• Must be in good health as determined by the Investigator, based on medical history and screening evaluations.

Key Exclusion Criteria:

• History of any clinically significant cardiac, endocrine, gastrointestinal (GI), hematologic, hepatic, immunologic, metabolic, urologic, pulmonary, neurologic, dermatologic, psychiatric, or renal disease, or other major disease, as determined by the Investigator
• Clinically significant abnormal laboratory test values, as determined by the Investigator, at Screening or Day -1
• History of, or positive test result at Screening for, human immunodeficiency virus (HIV)
• Treatment with any prescription or over-the-counter oral medication (excluding acetaminophen) within 14 days prior to Day -1 and an unwillingness or inability to refrain from this treatment during study participation, unless specifically permitted elsewhere within this protocol.
• Other unspecified reasons that, in the opinion of the Investigator or Sponsor, make the subject unsuitable for enrollment.

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply