A Study to Evaluate Vitamin B3 Derivative to Treat Mitochondrial Myopathy

Inclusion Criteria:

• Biochemically and/or genetically confirmed or confirmed primary mitochondrialmyopathy based on published diagnostic criteria.

• Biochemically confirmed mitochondrial disorder would mean that the patient meetsclinical criteria and has either biopsy or biochemical testing that supports thediagnosis.

• Confirmed mitochondrial disorder means that the patient meets published clinicalcriteria for the diagnosis and has also had confirmatory genetic testing for thedisorder type.

• Agreed to avoid vitamin supplementation or nutritional products with vitamin B3forms 14 days prior to the enrollment and during the study in order to not exceed 200 mg/day of vitamin B3 derivatives intake.

• Female of childbearing potential agreed to use effective contraception throughoutthe study.

• Written, informed consent to participate in the study.

Exclusion Criteria:

• Unwilling to comply with the follow-up schedule.

• Inability or refusal to give informed consent by the patient or a legally authorizedrepresentative.

• Known pregnancy or breastfeeding.

• Concurrent participation in another investigational drug study or within washoutperiod of treatment.

• Presence of other medical symptoms or condition, which may interfere withinterpretation of outcome measures as determined by the study PI.

Clinical / Laboratory Exclusion Criteria:

• Estimated Glomerular Filtration Rate (eGFR) < 30 mL/min.

• Patients in permanent Renal Replacement Therapy.

• Serum alkaline phosphatase 50% above normal limit.

• Serum aspartate transaminase 50% above normal limit.

• Serum Thyroxine (T4) 50% above or below normal limit.

• Serum Thyroid Stimulating Hormone (TSH) 50% above or below normal limit.

• Severe anemia with Hb < 7g/dL.

• Severe leukocytosis with WBC > 15,000/mm^3.