Estimated Enrollment:	608
Study Start Date:	March 2008
Estimated Study Completion Date:	April 2014
Estimated Primary Completion Date:	April 2014 (Final data collection date for primary outcome measure)

Detailed Description:

Inclusion Criteria:

To be eligible for enrollment into this study, subjects must meet the following eligibility criteria within 28 days prior to randomization:

• Subjects must have clinical features of HD and a confirmed family history of HD, OR a CAG repeat expansion ≥ 36.
• TFC > 9.
• Must be ambulatory and not require skilled nursing care.
• Age ≥ 16 years.
• Women must not be able to become pregnant (e.g., post menopausal, surgically sterile or using adequate birth control methods for the duration of the study).
• If psychotropic medications are taken (e.g., anxiolytics, hypnotics, benzodiazepines, antidepressants), they must be at a stable dosage for four weeks prior to randomization and should be maintained at a constant dosage throughout the study, as possible. (Note: stable dosing of tetrabenazine is allowable.) Any changes to these medications mandated by clinical conditions will be systematically recorded and the subject will be permitted to remain in the trial.
• Able to give informed consent and comply with trial procedures
• Able to take oral medication.
• May be required to identify an informant or caregiver who will be willing and able to supervise the daily dosing of study medications and to maintain control of study medications in the home.
• A designated individual will be identified by the subject to participate in the ongoing consent process should the subject's cognitive capacity to consent become compromised during participation in the study.

Exclusion Criteria:

• History or known sensitivity of intolerability to CoQ.
• Exposure to any investigational drug within 30 days of the Baseline visit.
• Clinical evidence of unstable medical illness in the investigator's judgment.
• Unstable psychiatric illness defined as psychosis (hallucinations or delusions), untreated major depression or suicidal ideation within 90 days of the Baseline visit.
• Substance (alcohol or drug) abuse within one year of the Baseline visit.
• Women who are pregnant or breastfeeding.
• Use of supplemental coenzyme Q10 within 30 days prior to the Baseline visit
• Clinically serious abnormalities in the screening laboratory studies (Screening creatinine greater than 2.0, alanine aminotransferase (ALT) or total bilirubin greater than 3 times the upper limit of normal, absolute neutrophil count of ≤1000/ul, platelet concentration of <100,000/ul, hematocrit level of <33 for female or <35 for male, or coagulation tests > 1.5 time upper limit of normal).
• Known allergy to FD&C yellow #5 or any other ingredient in the study drug (active and placebo)

Massachusetts General Hospital

University of Rochester

Huntington's disease Huntington disease HD coenzyme Q10 CoQ

Huntington Disease Basal Ganglia Diseases Brain Diseases Central Nervous System Diseases Nervous System Diseases Dementia Chorea Dyskinesias Movement Disorders Heredodegenerative Disorders, Nervous System Neurodegenerative Diseases

Genetic Diseases, Inborn Cognition Disorders Delirium, Dementia, Amnestic, Cognitive Disorders Mental Disorders Coenzyme Q10 Ubiquinone Micronutrients Growth Substances Physiological Effects of Drugs Pharmacologic Actions Vitamins