Multiple Doses of AT-1501-A201 in Adults With ALS

Inclusion Criteria: 1. ALS diagnosed as possible, laboratory supported probable, probable, or definite as defined by revised El Escorial criteria 2. ALS Functional Rating Scale - Revised (ALSFRS-R) Aggregate score of 37 or greater 3. No more than 24 months from diagnosis Exclusion Criteria: 1. Any other central or peripheral nervous system disease that may interfere with the evaluation of ALS or its progression 2. Presence of a tracheostomy, or use of permanent assistive ventilation (ventilatory support for 23 hours per day or more) 3. History of malignancy within the previous 5 years, except for localized non-melanoma skin cancers 4. Abnormal function of the immune system resulting from: * Clinical conditions affecting the immune system (e.g. HIV infection, agammaglobulinemia), * Systemic administration of corticosteroids (PO/IV/IM) at a dose equivalent to 20 mg/day of prednisone for more than 14 consecutive days within 90 days prior to screening, * Administration of anti-neoplastic and/or immunomodulating agents (e.g. Tumor necrosis factor alpha (TNF α) antagonists or anti-B cell antibodies) or radiotherapy within 1 year prior to screening. 5. Recipient of Stem Cell or Gene Therapy 6. Positive test for Hepatitis B surface antigen, Hepatitis C antibody, or HIV. 7. History of deep venous thrombosis or pulmonary embolism 8. History of active substance abuse within the past 2 years 9. History of stroke, poorly controlled or significant cardiovascular disease, diabetes