Inclusion Criteria:
- Patients with diagnosis of familial or sporadic ALS
- Onset of muscle weakness no more than 30 months before screening visit.
- Slow Vital Capacity (SVC) of at least 65% predicted for gender, age, ethnicity and height at Screening.
- If on riluzole, the dose must have been stable for at least 28 days prior to Baseline visit.
- Age 18 – 80 years inclusive.
- Female subjects may participate if they are of non-child-bearing potential or if they are of child-bearing potential they must agree to use the approved contraceptive methods
- Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) <=2x upper limit of normal (ULN); alkaline phosphatase and bilirubin <=1.5xULN.
- QTc (both QTcB and QTcF) <450 milliseconds (msec) or <480 msec for subjects with Bundle Branch Block at Screening and Baseline (average from triplicate ECGs).

Exclusion Criteria:
- Patients with other neuromuscular disorders (including a history of polio) which in the opinion of the investigator could have contributed to the muscular atrophy or weakness caused by ALS
- Patients with primary lateral sclerosis, monomelic ALS, ALS Parkinsonism dementia complex.
- Patients requiring non-invasive or mechanical ventilation (non-invasive ventilation for sleep apnoea is allowed subject to discussion with Medical Monitor)
- Patients on diaphragmatic pacing.
- Presence of any of the following clinical conditions: Drug abuse or alcoholism, uncontrolled hypertension, active major infectious disease, unstable psychiatric illness within 90 days of the Screening visit
- Subjects, who in the investigator's judgement, pose a significant suicide risk. - Current or chronic history of liver disease, known hepatic or biliary abnormalities (with the exception of Gilbert's syndrome or asymptomatic gallstones), positive Hepatitis B surface antigen or Hepatitis C antibody test.
- Subjects who have participated in a clinical trial involving receipt of a biopharmaceutical product within 6 months prior to the first dosing day.
- Exposure to non-biological experimental agents 1 month or 5 half-lives prior to Baseline visit (whichever is longer).
- History of sensitivity to ozanezumab, or components thereof, or a history of other allergies that, in the opinion of the investigator, contraindicates participation in the study.