Inclusion Criteria: 

• Able to comprehend and willing to sign an Informed Consent Form (ICF). If verbal consent is given, a Legal Designee of the patient must sign the ICF form 
• Completed participation on study drug and the Follow-Up Visit in the CY 4031 study 
• Male patients, who have not had a vasectomy AND confirmed zero sperm count, must agree for the duration of their participation in the study to either:
  • Use a condom during sexual intercourse with female partners who are of childbearing potential AND to have female partners use a highly effective means of contraception OR
  • Abstain from sexual intercourse during participation in the study 
• Female patients who are not post-menopausal (≥ 1 year) or sterilized, must: 
  • Not be breastfeeding
  • Have a negative pregnancy test
  • Have no intention to become pregnant during participation in the study AND 
  • Practice sexual abstinence, defined as refraining from intercourse during the duration of the study OR if male partners are not vasectomized with a confirmed zero sperm count, require use of a condom AND use of a highly effective contraceptive measure

Exclusion Criteria:

• Has a diaphragm pacing system (DPS) at study entry or anticipate DPS placement during the course of the study 
• Has taken an investigational study drug (other than tirasemtiv) prior to dosing, within 30 days or five half-lives of the prior agent, whichever is greater 
• Use of tizanidine and theophylline-containing medications during study participation
• Participation or planning to participate in any form of stem cell therapy for the treatment of ALS or another investigational drug