Study of Rapastinel as Monotherapy in Patients With MDD

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 induration at Visit 1

• Treatment naive in the current episode or have inadequate response to 1-3antidepressant therapies given at adequate dose and duration in the current episode

• If female of childbearing potential, have a negative serum β-human chorionicgonadotropin (β-hCG) pregnancy test

Exclusion Criteria:

• DSM-5-based diagnosis of any disorder other than MDD that was the primary focus oftreatment within 6 months before Visit 1

• Lifetime history of meeting DSM-5 criteria for:

• Schizophrenia spectrum or other psychotic disorder

• Bipolar or related disorder

• Major neurocognitive disorder

• Neurodevelopmental disorder of greater than mild severity or of a severity thatimpacts the participant's ability to consent, follow study directions, or otherwisesafely participate in the study

• Dissociative disorder

• Posttraumatic stress disorder

• MDD with psychotic features

• Significant suicide risk, as judged by the Investigator