AMX0035 in Patients With Amyotrophic Lateral Sclerosis (ALS)

Key Inclusion Criteria: 1. Male or female, aged 18-80 years of age 2. Sporadic or familial ALS diagnosed as definite as defined by the World Federation of Neurology revised El Escorial criteria 3. Less than or equal to 18 months since ALS symptom onset 4. Capable of providing informed consent and following trial procedures 5. Slow Vital Capacity (SVC) \>60% of predicted value for gender, height, and age at the Screening Visit 6. Subjects must either not take riluzole or be on a stable dose of riluzole for at least 30 days prior to the Screening Visit. Riluzole-naïve subjects are permitted in the study. 7. Women of child bearing potential (e.g. not post-menopausal for at least one year or surgically sterile) must agree to use adequate birth control for the duration of the study and 3 months after last dose of study drug. Women must not be planning to become pregnant for the duration of the study and 3 months after last dose of study drug 8. Men must agree to practice contraception for the duration of the study and 3 months after last dose of study drug. Men must not plan to father a child or provide for sperm donation for the duration of the study and 3 months after last dose of study drug Key Exclusion Criteria: 1. Presence of tracheostomy 2. Exposure to PB, Taurursodiol or UDCA within 3 months prior to the Screening Visit or planning to use these medications during the course of the study 3. History of known allergy to PB or bile salts 4. Abnormal liver function defined as aspartate aminotransferase (AST) and/or alanine aminotransferase (ALT) \> 3 times the upper limit of the normal 5. Renal insufficiency as defined by a serum creatinine \> 1.5 times the upper limit of normal 6. Poorly controlled arterial hypertension (systolic blood pressure (SBP)\>160mmHg or diastolic blood pressure (DBP)\>100mmHg) at the Screening Visit 7. Pregnant women or women currently breastfeeding 8. History of cholecystectomy 9. Biliary disease which impedes biliary flow including active cholecystitis, primary biliary cirrhosis, sclerosing cholangitis, gallbladder cancer, gallbladder polyps, gangrene of the gallbladder, abscess of the gallbladder. 10. History of Class III/IV heart failure (per New York Heart Association - NYHA) 11. Severe pancreatic or intestinal disorders that may alter the enterohepatic circulation and absorption of TUDCA including biliary infections, pancreatitis and ileal resection 12. The presence of unstable psychiatric disease, cognitive impairment, dementia or substance abuse that would impair ability of the subject to provide informed consent, according to Site Investigator judgment 13. Clinically significant unstable medical condition (other than ALS) that would pose a risk to the subject if they were to participate in the study 14. Active participation in an ALS clinical trial evaluating a small molecule within 30 days of the Screening Visit 15. Exposure at any time to any biologic under investigation for the treatment of subjects with ALS (off-label use or investigational) including cell therapies, gene therapies, and monoclonal antibodies. 16. Implantation of Diaphragm Pacing System (DPS)