Inclusion Criteria
1. Subjects must be diagnosed as having possible, probable, probable-laboratory supported, or definite ALS, either sporadic or familial according to modified El Escorial criteria.
2. Age 18 or above, able to provide informed consent, and comply with study procedures.
3. Vital capacity (VC) of at least 50% predicted value for gender, height and age at screening visit, or in the opinion of the study physician, able to safely tolerate study procedures.
4. Subject must be able to swallow oral medication at the Baseline Visit and expected to be able to swallow the capsules throughout the course of the study.
5. Received 23-valent pneumococcal vaccine within 4 years prior to starting clinical trial.
6. Subject must not have taken riluzole for at least 30 days, or be on a stable dose of riluzole for at least 30 days, prior to screening (riluzole-naïve participants are permitted in the study).
7. Women must not be able to become pregnant (e.g. postmenopausal, surgically sterile, or using adequate birth control) for the duration of the study and 3 months after study completion.
8. Males should practice contraception for the duration of the study and 3 months after completion.
9. Ability to safely lie flat for 90 min for PET procedures in the opinion of the study physician.
10. High or mixed affinity to bind TSPO protein (Ala/Ala or Ala/Thr) (Details below).
11. Upper motor Neuron Burden (UMNB) Score ≥25 at screening visit.
Exclusion Criteria
Subjects who meet any of the following criteria will be excluded from this study:
1. Abnormal liver function defined as AST and/or ALT > 3 times the upper limit of the normal.
2. Renal insufficiency as defined by a serum creatinine > 1.5 times the upper limit of normal.
3. The presence of unstable psychiatric disease, cognitive impairment, or dementia that would impair ability of the participant to provide informed consent, according to PI judgment.
4. Clinically significant unstable medical condition (other than ALS) that would pose a risk to the participant if they were to participate in the study.
5. History of HIV, clinically significant chronic hepatitis, or other active infection.
6. Active inflammatory condition of autoimmune disorder
7. Females must not be lactating or pregnant.
8. Active participation in another ALS clinical trial or exposure to an off label ALS experimental treatment within 30 days of the Baseline Visit
9. Exposure to immunomodulatory medications within 30 days of the Baseline Visit.
10. Any contraindication to undergo MRI studies such as:
a. History of a cardiac pacemaker or pacemaker wires
b. Metallic particles in the body
c. Vascular clips in the head
d. Prosthetic heart valves
e. Claustrophobia
11. Radiation exposure that exceeds the site™s current guidelines
12. Current use of tobacco products including cigarettes, cigars, snuff and chewing tobacco, or nicotine replacement products such as gum or patch
13. EKG finding of QTc prolongation > 450 ms for males and > 470 ms for females at screening or baseline.
