A Study of Aticaprant Plus an Antidepressant to Prevent Return of Depression Symptoms in Participants With Major Depressive Disorder Who Experience a Loss of Interest and Pleasure

Inclusion Criteria:

• Be medically stable based on physical examination (including a brief neurologicexamination), medical history, vital signs (including blood pressure), and 12-leadelectrocardiogram (ECG) performed at screening and OL baseline

• Be medically stable based on clinical laboratory tests performed at screening

• Meet DSM-5 diagnostic criteria for recurrent or single episode MDD, withoutpsychotic features upon clinical assessment and confirmed by the Structured ClinicalInterview for Diagnostic and Statistical Manual of Mental Disorders-5th Edition (DSM-5) Axis I Disorders-Clinical Trials version (SCID-CT)

• Have symptoms of anhedonia based on clinical assessment and confirmed by presence ofanhedonia (positive response to major depressive episode (MDE) module symptom Item

2. on the SCID-CT at screening

Exclusion Criteria:

• Has had no response to 2 or more consecutive antidepressant treatments administeredat adequate dose and duration in the current episode of depression including thecurrent selective SSRI/SNRI assessed using the Massachusetts General HospitalAntidepressant Treatment Response Questionnaire (MGH ATRQ)

• Has a history or evidence of clinically meaningful noncompliance with currentantidepressant therapy

• Has a history of moderate-to-severe substance use disorder including alcohol usedisorder according to DSM-5 criteria within 6 months before screening

• Has homicidal ideation/intent, per the investigator's clinical judgment, or hassuicidal ideation with some intent to act within 3 months prior to the start of thescreening phase

• Has cognitive impairment per investigator judgment that would render the informedconsent invalid or limit the ability of the participant to comply with the studyrequirements