This study is a phase 1, double-blind, placebo-controlled, multiple ascending dose study to determine the safety, tolerability, and pharmacokinetics of SAGE-718 oral solution in healthy adults (Part A) with an open-label cohort of patients with Huntington's disease (Part B)

This posting addresses Part B

Inclusion Criteria:

1. Subject is positive for mutant HTT (documented CAG repeats ≥ 40 units).
2. Subject has a body weight ≥50 kg and body mass index ≥18.0 and ≤30.0 kg/m2 at screening.

Exclusion Criteria:

1. Subject has any clinically significant abnormal finding on the physical exam at screening or admission.
2. Subject has a history or presence of a neurologic disease or condition (other than Huntington's disease), including but not limited to severe chorea, epilepsy, closed head trauma with clinically significant sequelae, or a prior seizure.
3. Subject has a family history of epilepsy.
4. Subject has a positive screening test for alcohol or drugs of abuse (including marijuana) at screening or admission.

Data sharing will be consistent with the results submission policy of ClinicalTrials.gov.