A Phase 2, to Evaluating the Safety and Efficacy of Pridopidine Vs Placebo for Symptomatic Treatment in Patients With Huntington's Disease

Originally, the study was designed to assess the effect of pridopidine on motor function at 26 weeks. Due to the recognition that the primary target of pridopidine is the Sigma-1 receptor, the trial was extended from 26 to 52 weeks to evaluate the effect of pridopidine on Total Functional Capacity (TFC). A minimum of 52 weeks are needed for the placebo group to decline and allow a window to assess an effect on TFC (a prespecified endpoint). Approximately 20% of patients completed 26 weeks of the study before IRB approvals for this extension, and did not continue into the 2nd treatment period up to 52 weeks.

Inclusion criteria

• Diagnosis of HD based on the presence of >/= 36 CAG repeats
• Male or female age ≥21 years, with an onset of HD after 18 years' old.
• Females of childbearing potential must be compliant in using adequate birth control throughout the duration of the study
• Body weight ≥50 kg
• Sum of >= 25 points on the UHDRS-TMS and UHDRS Independence Score <=90%
• Able and willing to provide written informed consent prior to any study related procedure.
• Willing to provide a blood sample for genetic analyses
• Willing and able to take oral medication and able to comply with the study specific procedures.
• Ambulatory, being able to travel to the study center, and judged by the investigator as likely to be able to continue to travel for the duration of the study.
• Availability and willingness of a caregiver, informant or family member to accompany the patient to the clinic at study, and the suitability of the caregiver should be judged by the Investigator.

• Other criteria apply, please contact the investigator for more information.

Exclusion criteria

• Patients with clinically significant heart disease at the screening visit
• Treatment with tetrabenazine within 6 weeks of study screening
• Patients with a history of epilepsy or of seizures within the last 5 years
• Have other serious medical illnesses in the opinion of the investigator may put the patient at risk when participating in the study or may influence the results of the study or affect the patient's ability to take part in the study
• Patients receiving medications (within the last 6 weeks prior to screening) that have been proven to prolong QT interval or who may require such medications during the course of the study such as but not limited to non allowed anti psychotic medications, tricyclic antidepressants and/or Class I antiarrhythmics

• Other criteria apply, please contact the investigator for more information