A Study to Evaluate SAGE-217 in Subjects With Moderate to Severe Major Depressive Disorder

Part A of the study is an open-label design with dosing of SAGE-217 for 14 days.

Part B of the study is a randomized, double-blind, parallel-group, placebo-controlled design.
Eligible subjects will be randomized to SAGE-217 or placebo for 14 days.

Inclusion Criteria:

- Subject has a diagnosis of Major Depressive Disorder that has been present for at
least a 4-week period as diagnosed by Structured Clinical Interview for DSM-IV Axis I
Disorders (SCID-I)

Exclusion Criteria:

- Subject has a history of suicide attempt

- Subject has a history of treatment-resistant depression, defined as persistent
depressive symptoms despite treatment with adequate doses of antidepressants from two
different classes for an adequate amount of time

- Active psychosis

- Medical history of seizures

- Medical history of bipolar disorder, schizophrenia, and/or schizoaffective disorder