A Study of TCD601 (Siplizumab) in Newly Diagnosed Adult Amyotrophic Lateral Sclerosis (ALS) Patients

Key Inclusion Criteria: * Male or female patients ≥ 18 to 80 years of age. * Diagnosis of ALS by revised El Escorial Criteria, at study entry within 24 months of first symptoms. * Patients on existing ALS treatment must have been on a stable dose for 28 days. Key Exclusion Criteria: * Patient with severe systemic infections, current or within the two weeks prior to randomization. * Subjects who, in the opinion of the investigator, are not capable of giving informed consent for the study or who are unable or unwilling to adhere to the study requirements outlined in the protocol. * Use of other investigational products or treatment in another investigational drug study within 30 days of screening * Pregnant or nursing (lactating) women.