This study is a phase 1, double-blind, placebo-controlled crossover study of single, oral dose of SAGE-718 using a 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 ≥18.0 and ≤30.0 kg/m2 at screening.
2. If female, subject is post-menopausal (at least 12 months of spontaneous amenorrhea with confirmatory follicle stimulating hormone >40 mIU/mL), or surgically sterile (bilateral tubal ligation, bilateral oophorectomy, and/or hysterectomy).
3. Subject is healthy with no history or evidence of clinically relevant medical disorders as determined by the Investigator.

Exclusion Criteria:

1. Subject has a history or presence of any psychiatric disease or condition including suicidal ideation or behavior, has answered YES to any question on the C-SSRS at screening or admission, or is currently at risk of suicide in the opinion of the Investigator.
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 family history of epilepsy.
4. Subject has obstructed venous access and/or has skin disease, rash, acne, or abrasion at venous access site that may affect the ability to obtain a PK sample or affect the ability to receive the ketamine infusions.
5. Subject has had previous exposure to or is known to be allergic to ketamine or any of its excipients.

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