Study Evaluating the Safety, Tolerability, and Pharmacokinetics of Single Doses and Multiple Doses of BIIB059 in Healthy Volunteers and Participants With Systemic Lupus Erythematosus

Part 1 (single ascending dose in healthy volunteers) has closed to enrollment.

Part 1: Key Inclusion Criteria For Healthy Volunteers:

- Be in good health as determined by the Investigator, based on medical history,
physical examination, and 12-lead ECG.

- Body mass index (BMI) between 18 and 30 kg/m2 and body weight ≥45 kg.

Part 1: Key Exclusion Criteria For Healthy Volunteers:

- History of or positive test results at screening for the following: for human
immunodeficiency virus (HIV), hepatitis C virus antibody (HCV Ab), hepatitis B virus
(defined as positive for hepatitis B surface antigen [HBsAg] or hepatitis B core
antibody [HBcAb]).

- - History of chronic, recurrent, or recent serious infection (e.g., pneumonia,
septicemia) as determined by the Investigator within 3 months prior to screening and
randomization.

- History of severe allergic or anaphylactic reactions or history of allergic reactions
likely to be exacerbated by any component of the study drug.

- History of any clinically significant cardiovascular, endocrinologic, hematologic,
hepatic, immunologic, metabolic, urologic, pulmonary, neurologic, dermatologic,
psychiatric, renal, or other major disease, as determined by the Investigator.

- Any live or attenuated immunization/vaccination within 1 month prior to randomization
or planned to occur during the study period.

- Blood donation (1 unit or more) within 1 month prior to randomization.

- Vigorous exercise (e.g., jogging, swimming laps, heavy gardening, hiking uphill, etc.)
within 48 hours prior to Day -1

Part II: Key Inclusion Criteria for SLE Participants:

- Definite SLE for at least 6 months duration or anti-dsDNA antibody, prior to
screening.

- Presence of active lupus skin disease including acute, sub acute, and/or chronic
cutaneous lupus (e.g., discoid) at the time of screening and randomization.

- BMI between 18 and <40 kg/m2 and body weight ≥45 kg.

Part II: Key Exclusion Criteria for SLE Participants:

- Active neuropsychiatric SLE including but not limited to the following: seizure, new
or worsening impaired level of consciousness, psychosis, delirium or confusional
state, aseptic meningitis, ascending or transverse myelitis, chorea, cerebellar
ataxia, mononeuritis multiplex, or demyelinating syndromes.

- History of chronic, recurrent, or recent serious infection (e.g., pneumonia,
septicemia) as determined by the Investigator within 3 months prior to screening and
randomization.

- Symptoms of bacterial or viral infection (including upper respiratory tract infection)
within 28 days prior to randomization.

- History of severe allergic or anaphylactic reactions or history of allergic reactions
likely to be exacerbated by any component of the study drug.

- Evidence of skin conditions other than lupus skin disease (e.g., eczema) at screening
or at the time of randomization that would interfere with evaluations of the effect of
study treatment on lupus skin disease.

- Treatment with oral prednisone >15 mg daily (or equivalent). Any prednisone regimen
must be stable for at least 28 days before randomization and expected to remain stable
for the duration of the study.

- Treatment with any antibiotics within 14 days prior to randomization.

Part IIIa: Key Inclusion Criteria for Healthy Volunteers :

- Must be in good health as determined by the Investigator, based on medical history,
physical examination, and 12-lead ECG.

- Must have a body mass index (BMI) between 18 and 30 kg/m2 and body weight ≥45 kg.

Part IIIa: Key Exclusion Criteria for Healthy Volunteers:

- History of chronic, recurrent, or recent serious infection (e.g., pneumonia,
septicemia) as determined by the Investigator within 3 months prior to screening and
randomization

- History of severe allergic or anaphylactic reactions or history of allergic reactions
likely to be exacerbated by any component of the study treatment.

- Treatment with any antibiotics within 14 days prior to randomization.

Part IIIb: Key Inclusion Criteria for SLE Participants:

- Definite SLE for at least 6 months duration prior to screening

- Presence of active lupus skin disease including acute, subacute, and/or chronic
cutaneous lupus (e.g., discoid), and/or hypocomplementemia , and/or positive
anti-dsDNA antibody at the time of screening.

- Must have a BMI between 18 and <40 kg/m2 and body weight ≥45 kg.

Part IIIb: Key Exclusion Criteria for SLE Participants:

- Active neuropsychiatric SLE including but not limited to the following: seizure, new
or worsening impaired level of consciousness, psychosis, delirium or confusional
state, aseptic meningitis, ascending or transverse myelitis, chorea, cerebellar
ataxia, mononeuritis multiplex, or demyelinating syndromes.

- History of chronic, recurrent, or recent serious infection (e.g., pneumonia,
septicemia) as determined by the Investigator within 3 months prior to screening and
randomization.

- History of severe allergic or anaphylactic reactions or history of allergic reactions
likely to be exacerbated by any component of the study drug.

- Treatment with any antibiotics within 14 days prior to randomization.

NOTE: Other protocol-defined inclusion/exclusion Criteria May Apply