Extension Study Following the Studies MT-1186-A03 or A04 to Evaluate the Safety of Oral Edaravone in Subjects With ALS

Inclusion Criteria: * Subjects must provide a signed and dated informed consent form (ICF) to participate in the study. * Subjects must be able (in the judgment of the Investigator) to understand the nature of the study and all risks involved with participation in the study * Subjects must be willing to cooperate and comply with all protocol restrictions and requirements. * Subjects who successfully complete Week 96 of Study MT-1186-A03 or Week 48 of Study MT-1186-A04 and have been compliant with study drug (80-120%). Exclusion Criteria: * Subjects of childbearing potential unwilling to use a highly effective method of contraception from the Visit #1 until 3 months after the last dose of study medication. * Subjects who have a significant risk of suicide. Subjects with any suicidal behavior or suicidal ideation of type 4 (active suicidal ideation with some intent to act, without a specific plan) or type 5 (active suicidal ideation with specific plan and intent) based on the C-SSRS at Week 96 of the A03 study or at Week 48 of the A04 study. * Subjects who are not eligible to continue in the study, as judged by the Investigator.