Inclusion Criteria:

• Sporadic or familial ALS diagnosed as clinically possible, probable, lab-supported probable, or definite ALS defined by revised El Escorial criteria.
• Age 18 years or older.
• Capable of providing informed consent and complying with study procedures, in the SI’s opinion.
• Time since onset of weakness due to ALS ≤ 36 months at the time of the Master Protocol Screening Visit.
• SVC ≥ 50% of predicted capacity for age, height, and sex at the time of the Master Protocol Screening Visit.
• Participants must either not take riluzole or be on a stable dose of riluzole for ≥ 30 days prior to the Master Protocol Screening Visit. Riluzole-naïve participants are permitted in the study.
• Participants must either not take edaravone or have completed at least one cycle of edaravone prior to the Master Protocol Screening Visit. Edaravone-naïve participants are permitted in the study.
• Participants must have the ability to swallow pills and liquids at the time of the Master Protocol Screening Visit and, in the SI’s opinion, have the ability to swallow pills for the duration of the study.
• Geographically accessible to the site.

Exclusion Criteria:

• Clinically significant unstable medical condition (other than ALS) that would pose a risk to the participant, according to SI’s judgment (e.g., cardiovascular instability, systemic infection, untreated thyroid dysfunction, or clinically significant laboratory abnormality or EKG changes). Lab abnormalities include, but are not limited to:
  • Hemoglobin < 10 g/dL;
  • White Blood Cells < 3.0 x 103/mm^3;
  • Neutrophils, Absolute ≤ 1000/mm^3;
  • Eosinophilia (absolute eosinophil count of ≥ 500 eosinophils per microliter);
  • Low platelet counts (< 150 x 10^9 per liter);
  • Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) greater than 3  times the upper limit of normal (ULN);
  • eGFR < 30 mL/min/1.73m^2;
  • thyroid-stimulating hormone (TSH) levels >10 mIU/L or < 0.01 mIU/L. 
• Presence of unstable psychiatric disease, cognitive impairment, dementia or substance abuse that would impair ability of the participant to provide informed consent, in the SI’s opinion.
• Active cancer or history of cancer, except for the following: basal cell carcinoma or successfully treated squamous cell carcinoma of the skin, cervical carcinoma in situ, prostatic carcinoma in situ, or other malignancies curatively treated and with no evidence of disease recurrence for at least 3 years.
• Use of investigational treatments for ALS (off-label use or active participation in a clinical trial) within 5 half-lives (if known) or 30 days (whichever is longer) prior to the Master Protocol Screening Visit. (Please refer to the Manual of Procedures (MOP) for current list of experimental therapies).
• Exposure at any time to any gene therapies under investigation for the treatment of ALS (off-label use or investigational).
• If female, breastfeeding, known to be pregnant, planning to become pregnant during the study, or of child-bearing potential and unwilling to use effective contraception for the duration of the trial and for 3 months, or longer as specified in each RSA, after discontinuing study treatment.
• If male of reproductive capacity, unwilling to use effective contraception for the duration of the trial and for 3 months, or longer as specified in each RSA, after discontinuing study treatment.
• Anything that would place the participant at increased risk or preclude the participant’s full compliance with or completion of the study, in the SI’s opinion.
• If a participant is being re-screened, the disqualifying condition has not been resolved, or the mandatory wash-out duration has not occurred.
• For those participating in the optional CSF collection, contraindication to undergoing a lumbar puncture (LP) in the SI’s opinion. Participants undergoing the LP must not be currently taking anticoagulation medications such as warfarin that would be a contraindication to LP; aspirin and non-steroidal anti-inflammatories are allowed.