This is a multi-center, open-label study of MN-166 (ibudilast) in subjects with ALS. To be eligible subjects must meet the El Escorial criteria of possible, laboratory-supported probable, probable, or definite criteria for a diagnosis of ALS. Safety, tolerability, blood, neuro-imaging biomarkers, and clinical outcomes will be collected on all subjects. Subjects will receive study drug for 36 weeks.