The purpose of this study is to determine if oral treatment with ONO-2506PO in patients diagnosed with ALS, who have had onset of muscle weakness within 14 months of randomization, could lead to the slowing of decline in respiratory function, functional status, muscle strength, quality of life and survival compared with placebo group.

Inclusion Criteria:

1. Diagnosis of clinically possible, clinically probable laboratory-supported, clinically probable or clinically definite ALS (according to WNF EL Escorial diagnostic criteria, revised according to the Airlie House Conference 1998)
2. Onset of muscle weakness within 14 months randomization
3. Concomitant standard Riluzole therapy (50mg twice daily)

Exclusion Criteria:

1. Presence of a tracheotomy, mechanical ventilation or non-invasive ventilation
2. Requirement for prescription drugs used for potential neuroprotective benefit -