Inclusion Criteria:

1. Diagnosis of clinically definite ALS, clinically probable-laboratory supported ALS, or clinically probable ALS based on revised El Escorial criteria.
2. ALS symptom onset ≤ 2 years prior to the Screening Visit.
3. Subjects who have been on riluzole may enter the study if they have been on a stable dose of 50 mg BID for ≥ 4 weeks prior to the Screening Visit and, if possible, should remain on that dose throughout the study.
4. Forced vital capacity (FVC) ≥ 60% at the Screening Visit.
5. Systolic blood pressure ≤ 140 mm Hg and a mean diastolic blood pressure of ≤ 90 mm Hg at the Screening and Baseline Visits.

Exclusion Criteria:

1. History of use of adrenocorticotropic hormone (ACTH) preparations for treatment of ALS.
2. Any medical condition known to have an association with motor neuron dysfunction (other than ALS) which might confound or obscure the diagnosis of ALS.
3. Subject has tracheostomy, diaphragm pacing, or ongoing (used for greater than 7 consecutive days in the 4 weeks prior to the Screening Visit) need for assisted ventilation of any type.
4. History of chronic active hepatitis including active or chronic hepatitis B, or acute or chronic hepatitis C.
5. History of tuberculosis (TB) infection, any signs/symptoms of TB, or any close contact with an individual with an active TB infection.
6. Clinically significant infection requiring intravenous administration of antibiotics and hospitalization in the 4 weeks prior to the Screening Visit.
7. Subject has used edaravone in the 1 week prior to the Screening Visit or in the 2 weeks prior to the Randomization Visit.