• Patients diagnosed with laboratory supported probable, clinically probable or definite ALS according to the World Federation of Neurology Revised El Escorial criteria

• Patient with a familial or sporadic ALS

• ALS disease duration from diagnosis no longer than 24 months at the screening visit

• Patient treated with a stable dose of riluzole (100 mg/day) for at least 12 weeks days prior to the baseline visit

• Patient with an ALSFRS-R score progression between onset of the disease and screening of \> 0.3 per month, confirmed with an ALSFRS-R score progression of ≥ 1 point during a 12-week run-in period between screening and randomization.

• Patient with a score, at screening, of at least 26 overall, including a score of at least 3 on item #3 and at least 2 on each of the 12 ALSFRS-R individual component items and with a score, at randomization, of at least 2 on each of the 12 ALSFRS-R individual component items