Alternatives for Reducing Chorea in Huntington Disease
Condition: Chorea Associated With Huntington Disease
MeSH terms: Huntington Disease; Chorea
Intervention: SD-809
Intervention description: SD-809 tablets will be provided in dose strengths of 6, 9 and 12 mg.
Phase: Phase 3
Study type: Interventional
Primary purpose: Treatment
Allocation: Non-Randomized
Intervention model: Single Group Assignment
Masking: None (Open Label)
Enrollment: 119.0
Sex: All
Minimum age: 18 Years
Healthy volunteers: No
Keywords: Chorea; Huntington Disease

Summary:

      The purpose of this study is to evaluate the safety, tolerability, and pharmacokinetics of
      SD-809 extended release (ER) in participants switching from tetrabenazine to SD-809 ER. In
      addition, the safety and tolerability of long-term treatment with SD-809 ER will be assessed
      in "Switch" participants as well as "Rollover" participants completing a randomized, double
      blind, placebo-controlled study of SD-809 ER.
    

Eligibility criteria:

        Inclusion Criteria:

          -  Participant is at least 18 years of age or the age of majority (whichever is older) at
             Screening.

          -  Participant has been diagnosed with manifest HD, as indicated by characteristic motor
             exam features, and has a documented expanded cytosine adenine guanine (CAG) repeat
             (greater than or equal to >= [37]) at or before Screening.

          -  Participant meets either of the following:

               1. Has successfully completed participation in the First-HD Study (SD-809-C-15) or

               2. Has been receiving an Food and Drug Administration (FDA)-approved dose of
                  tetrabenazine that has been stable for >=8 weeks before Screening and is
                  providing a therapeutic benefit for control of chorea.

          -  Participant has a Total Functional Capacity (TFC) score >=5 at Screening.

          -  Participant is able to swallow study medication whole.

          -  Participant has provided written, informed consent or, a legally authorized
             representative (LAR) has provided written informed consent and the subject has
             provided assent.

          -  Participant has provided a Research Advance Directive.

          -  Female participants of childbearing potential agree to use an acceptable method of
             contraception from screening through study completion.

          -  The participant has a reliable caregiver who interacts with the participant on a daily
             basis, oversees study drug administration, assures attendance at study visits and
             participates in evaluations, as required.

          -  Participant is able to ambulate without assistance for at least 20 yards (Note: The
             use of assistive devices (such as; walker, cane) are permitted during ambulation).

          -  Has sufficient reading skills to comprehend the participant completed rating scales.

        Exclusion Criteria:

          -  Participant has a serious untreated or under-treated psychiatric illness, such as
             depression, at Screening or Baseline.

          -  Participant has active suicidal ideation at Screening or Baseline.

          -  Participant has history of suicidal behavior at Screening or Baseline.

          -  Participant has evidence for depression at Baseline.

          -  Participant has an unstable or serious medical illness at Screening or Baseline.

          -  Participant has received tetrabenazine within 7 days of Baseline (Rollover
             participants only).

          -  Participant has received any of the following concomitant medications within 30 days
             of Screening or Baseline: Antipsychotics, Metoclopramide, Monoamine oxidase inhibitors
             (MAOI), Levodopa or dopamine agonists, Reserpine, Amantadine, Memantine (Rollover
             participants only)

          -  Switch participants may receive Memantine if on a stable, approved dose for at least
             30 days

          -  Participant has significantly impaired swallowing function at Screening or Baseline.

          -  Participant has significantly impaired speaking at Screening or Baseline.

          -  Participant requires treatment with drugs known to prolong the QT interval.

          -  Participant has prolonged QT interval on 12-lead electrocardiogram (ECG) at Screening.

          -  Participant has evidence of hepatic impairment at Screening.

          -  Participant has evidence of significant renal impairment at Screening.

          -  Participant has known allergy to any of the components of study medication.

          -  Participant has participated in an investigational drug or device trial other than
             SD-809-C-15 within 30 days (or 5 drug half-lives) of Screening, whichever is longer.

          -  Participant is pregnant or breast-feeding at Screening or Baseline.

          -  Participant acknowledges present use of illicit drugs at Screening or Baseline.

          -  Participant has a history of alcohol or substance abuse in the previous 12 months.