28-Day Study of SAGE-718 on Functioning Capacity in Participants With Huntington's Disease

Inclusion Criteria

• •For all
• •1. Agree to refrain from drugs of abuse for the duration of the study and from alcohol during the 48 hours preceding each study visit.
• •Additional criteria for participants with HD only:
• •2. Be ambulatory, able to travel to the study center, and, judged by the investigator, is likely to be able to continue to travel to the study center to complete study visits for the duration of the study.
• •3. Have:
• •1. Genetically confirmed disease with cytosine, adenine, and guanine (CAG) expansion ≥36.
• •2. At screening, Unified Huntington's Disease Rating Scale (UHDRS) Total Functional Capacity (TFC) \>6 and \<13, suggesting no more than a moderate level of functional impairment.
• •3. No features of juvenile HD.
• •4. CAG-Age-Product (CAP) score \>70, as calculated using the CAP formula: Age × (CAG - 30) / 6.49.
• •5. Score of 15 to 25 (inclusive) on the Montreal Cognitive Assessment (MoCA) at screening, indicating the presence of cognitive impairment.
• •Additional criteria for HP only:
• •1. Score ≥26 on the MoCA at screening.
• •2. Have no known family history of HD; or, have known family history of HD but have genetic test results available that show a normal CAG repeat length for both Huntingtin (HTT) alleles (\<36).