The purpose of this study is to evaluate the safety of oral edaravone at a dose of 105 mg administered once daily for 10 days out of a 14-day period, followed by a 14-day drug-free period. This study will be continued until the earlier date when oral edaravone is commercially available at each site in Japan or August 2023.

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.

up to 8 months

This study was a single arm open-label study including the following one single set of dosing regimen specified in the study protocol: 28 days per cycle, study drugs were received for 10 days in the first 2 weeks and subsequently were not received for the rest 2 weeks. The dosing regimen was not divided into Treatment Period or Drug-Free Period since this was a single arm study. Therefore, AE were not collected respectively per specific intervention in this study.