This study is a Phase 1, randomized, double-blind, placebo-controlled study of multiple doses of SAGE-718 using ketamine challenge to evaluate the electrophysiology, safety, tolerability, and pharmacokinetics in healthy subjects.

Inclusion Criteria:

1. Subject has a body weight ≥50 kg and body mass index (BMI) ≥18.0 and ≤30.0 kg/m2 at screening.
2. Subject is healthy with no history or evidence of clinically relevant medical disorders as determined by the Investigator.

Exclusion Criteria:

1. Subject has any clinically significant abnormal value for hematology, clinical chemistry, or urinalysis at screening or admission.
2. Subject has a history or presence of a neurologic disease or condition, including but not limited to epilepsy, closed head trauma with clinically significant sequelae, or a prior seizure.
3. 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.