Main Inclusion Criteria:  Age 18 - 80 years (both inclusive), male or female; Diagnosis of definite, probable, probable laboratory supported or possible ALS as based on the El Escorial and the revised Airlie House diagnostic criteria for ALS;  Onset of first symptoms* no longer than 24 months prior to randomization;  *Date of onset is the date the patient reported one or more of the following symptoms:  Muscle weakness in limbs Speech/swallowing difficulties Respiratory symptoms: dyspnea was noticed SVC equal to or more than 70% of the predicted normal value for gender, height and age at screening visit; Change in ALSFRS-R score between 0.35 points and 1.5 points per month (both inclusive) in the period from onset of first symptoms to the Screening visit; Capable of providing informed consent and complying with trial procedures.  Main Exclusion Criteria:  Diagnosis of Primary Lateral Sclerosis; Diagnosis of Frontotemporal Dementia; Diagnosis of other neurodegenerative diseases (e.g. Parkinson disease, Alzheimer disease); Diagnosis of polyneuropathy; Other causes of neuromuscular weakness; Have a significant pulmonary disorder not attributed to ALS and/or require treatment interfering with the evaluation of ALS on respiratory function; Use of intravenous (IV) edaravone within 6 months of the screening visit; Depend on mechanical ventilation (invasive or non-invasive) or require tracheostomy at Screening; Renal impairment as indicated by a creatinine clearance of less than 50 mL/min as calculated by the Cockcroft Gault equation; Subject has a history of clinically significant hepatic disease, hepatitis or biliary tract disease, or subject has a positive screening test for HIV, hepatitis B or C;