Futility analysis failed to showed likelihoo of benefit of CoQ 2400 mg/day.

The goals of this trial are to determine if coenzyme Q10 is effective in slowing the worsening symptoms of Huntington's disease and to learn about the safety and acceptability of long-term coenzyme Q10 use by determining its effects on people with Huntington's disease.

Huntington's disease (HD) is a slowly progressive disorder that devastates the lives of those affected and their families. There are no treatments that slow the progression of HD, only mildly effective symptomatic therapies are available.

The purpose of this trial is to find out if coenzyme Q10 (CoQ) is effective in slowing the worsening symptoms of HD. In this study, researchers also will learn about the safety and acceptability of long-term CoQ use by determining its effects on people with HD.

Participants in this trial will be randomly chosen to one of two groups. Group 1 will receive CoQ (2400 mg/day), and group 2 will receive a placebo (an inactive substance). Researchers will compare the change in total functional capacity (TFC)-a measure of functional disability-in the two groups. The TFC is a valid and reliable measure of disease progression and is particularly responsive to change in the early and mid-stages of HD. Researchers will also compare the changes in other components of the Unified Huntington's Disease Rating Scale '99 (UHDRS) including: the total motor score, total behavioral frequency score, total behavior frequency X severity score, verbal fluency test, symbol digit modalities test, Stroop, interference test, functional checklist, and independence scale scores. The groups will also be compared with respect to tolerability, adverse events, vital signs, and laboratory test results as measures of safety.

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)