Effect of PBT2 in Patients With Early to Mid Stage Huntington Disease

Inclusion Criteria:

- Patients who:

1. Provide signed informed consent in accordance with local regulations.

2. Have Huntington disease including clinical features of HD and a CAG repeat
number ≥ 36.

3. Have a Total Functional Capacity between 6 and 13, inclusive.

4. Have cognitive impairment as demonstrated by a MoCA score of ≥ 12.

5. Are ≥ 25 years of age.

6. If taking tetrabenazine, have been on a stable dose for at least 3 months.

7. If female, are either a) of childbearing potential and compliant in using
adequate birth control or b) not of childbearing potential.

8. If male, is either a) of reproductive potential and compliant in using adequate
birth control or b) not of reproductive potential.

9. Have a study partner who is willing to provide consent and spends on average at
least two hours a day for at least four days a week with the patient, is fluent
in the English language, and who agrees to attend certain study visits and
provide accurate information about the patient.

10. Are able to swallow oral capsules.

11. Are fluent in the English language for the administration of rating scales and
have sufficient visual, hearing and motor skills to complete procedures.

Exclusion Criteria:

- Patients who:

1. Have an allergy to PBT2 or its excipients.

2. Have other known primary neurodegenerative disorders associated with dementia.

3. Have known dementia syndromes due to non-primary CNS disease.

4. Have another condition that in the investigator's judgment is resulting in
clinically significant cognitive impairment.

5. In the opinion of the investigator, have any clinically significant uncontrolled
medical or psychiatric illness, including history of seizures.

6. Have clinically significant cardiovascular, hepatic, renal, pulmonary, metabolic
or endocrine disease that, in the opinion of the investigator, would interfere
with an individual's participation in the study.

7. Have a calculated creatinine clearance at Screening of <50mL/min.

8. Have a history of malignancy diagnosed within 2 years of Screening.

9. Are pregnant or lactating females.