A Study of Rapastinel as Adjunctive Therapy in the Prevention of Relapse in Patients With Major Depressive Disorder

Inclusion Criteria:

- Meet Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5)
criteria for MDD

- Current major depressive episode of at least 8 weeks and not exceeding 18 months in
duration at Screening

- Have no more than partial response (< 50% improvement) to ongoing treatment with a
protocol-allowed antidepressant

- If female of childbearing potential, have a negative serum β-human chorionic
gonadotropin (β-hCG) pregnancy test.

Exclusion Criteria:

- DSM-5-based diagnosis of any disorder other than MDD that was the primary focus of
treatment within 6 months before Screening

- Lifetime history of meeting DSM-5 criteria for:

1. Schizophrenia spectrum or other psychotic disorder

2. Bipolar or related disorder

3. Major neurocognitive disorder

4. Neurodevelopmental disorder of greater than mild severity or of a severity that
impacts the participant's ability to consent, follow study directions, or
otherwise safely participate in the study

5. Dissociative disorder

6. Posttraumatic stress disorder

7. MDD with psychotic features

- Significant suicide risk, as judged by the Investigator.