Clinical Trial of Ultra-high Dose Methylcobalamin for ALS

Inclusion Criteria: Treatment and OLE Phase: * ALS patients within 12 months after clinical onset at the entry * Diagnosed based on updated Awaji criteria: definite, probably or laboratory supported probable * Decline of ALSFRSR being 1 or 2 during observation period of 12 weeks * Japanese Clinical Severity Scale 1 or 2 * Those who can visit the participating medical centers Tsunagi Phase: \- The subjects for the Tsunagi phase are patients with ALS who are continuing the administration of this drug at the time of approval, and have obtained consent for the transition to the Tsunagi phase. Exclusion Criteria: Treatment and OLE Phase: * Those who have tracheostomy * Those who had NIPPV * %FVC\<60% * Those who have Chronic Obstructive Pulmonary Disease (COPD) * Those who have symptoms and signs of B12 deficiency * Those who had edaravone less than 4 weeks prior to entry * Those who changed the schedule and dosing of riluzole * Those who have dementia * Those who have the possibility of pregnancy * Those who have serious respiratory or cardiac diseases * Those who have malignancies * Those who participated other clinical trials within 12 weeks * Those who have allergies to B12 and related compounds Tsunagi Phase: Not applicable.