Study in PRE-manifest Huntington's Disease of Coenzyme Q10 (UbiquinonE) Leading to Preventive Trials (PREQUEL)

secondary objectives:

1. To assess the change from baseline to 20 weeks on biomarkers of oxidative stress (8OHdG
and 8OHrG) and DNA repair mechanisms (OGG1) in pre-manifest participants treated with
600, 1200 or 2400 mg per day of CoQ10.

2. To assess the dose-response relationship between CoQ10 at dosages of 600, 1200 or 2400
mg per day and 8OHdG/8OHrG and OGG1.

3. To assess the serum levels of CoQ10 at 600, 1200 or 2400 mg in pre-manifest participants
and their relationship to 8OHdG/8OHrG and OGG1.

4. To assess the feasibility of implementing a preventive therapeutic trial in a
pre-manifest population.

5. To assess the utility and stability of clinical measures of HD, social relations,
behavior and employment in a pre-manifest sample enrolled in a treatment trial.

Inclusion Criteria:

- Participants will be positive for the CAGn expansion in the Huntingtin gene (>36
repeats) and be pre-manifest by virtue of scoring 3 or less on diagnostic confidence
level (Question 17 of the UHDRS)

- Participants will have received genetic testing prior to enrollment through a standard
pre-manifest testing protocol.

- 18 years of age or older.

- Concomitant medications are permitted with the exception of CoQ10, creatine > 5g/day
and warfarin.

Exclusion Criteria:

- History of intolerability to CoQ10.

- CoQ10 use within 60 days prior to randomization.

- Unstable medical or psychiatric illness;

- Substance abuse within one year of the baseline visit.

- Pregnancy, breastfeeding or lack of reliable contraception in women of childbearing
age.

- Subjects with known allergy to FD&C #6 yellow food coloring.