Long-Term Safety and Efficacy Evaluation of EPI-743 in Children With Leigh Syndrome

Inclusion Criteria: 1. Diagnosis of Leigh syndrome with genetic confirmation 2. Completion of EPI743-12-002 protocol and initiation of treatment within 14 days of Month 12 visit in EPI743-12-002 study 3. Participant or participant's guardian able to consent and comply with protocol requirements 4. Continued abstention from supplements excluded in EPI743-12-002 study 5. Botox® is allowed if approved by the sponsor Exclusion Criteria: 1. Allergy to EPI-743 or sesame oil 2. Allergy to vitamin E 3. Clinical history of bleeding or abnormal baseline prothrombin time (PT)/partial thromboplastin time (PTT) 4. Hepatic insufficiency with liver function tests (LFTs) greater than two times upper limit of normal 5. Renal insufficiency requiring dialysis 6. End-stage cardiac failure 7. Fat malabsorption syndromes precluding drug absorption 8. Use of anticoagulant medications 9. Participation in other clinical research studies/taking other experimental agents 10. Participation in elective procedures that required sedation