A Randomized, Double-blind, Multicenter, Placebo-controlled Study of Adjunctive Aticaprant Plus an Antidepressant for Relapse Prevention in Major Depressive Disorder (MDD) With Moderate-to-severe Anhedonia

Prior treatment

• Has one or more of the following diagnoses: A current or prior (lifetime) DSM-5 diagnosis of: a psychotic disorder or MDD with psychotic features; bipolar or related disorders; intellectual disability; autism spectrum disorder; personality disorders (borderline, antisocial, histrionic, narcissistic); somatoform disorders. A primary DSM-5 diagnosis (which has been the primary focus of psychiatric treatment within the past 2 years) of: panic disorder; generalized anxiety disorder; social anxiety disorder; specific phobia (allowed as secondary diagnosis); A current (in the past year) DSM-5 diagnosis of:obsessive-compulsive disorder (OCD),post-traumatic stress disorder (PTSD),anorexia nervosa, bulimia nervosa (allowed if stable for 1 year)
• Has homicidal ideation/intent, per the investigator’s clinical judgment, or has suicidal ideation with some intent to act within 3 months prior to the start of the screening phase, per the investigator’s clinical judgment or based on the C-SSRS, corresponding to a response of “Yes” on Item 4 (active suicidal ideation with some intent to act, without specific plan) or Item 5 (active suicidal ideation with specific plan and intent) for suicidal ideation on the C-SSRS, or a history of suicidal behavior within the past 6 months prior to the start of the screening phase. Participants reporting suicidal ideation with intent to act or suicidal behavior at OL baseline should be excluded
• Has a history of moderate-to-severe substance use disorder including alcohol use disorder according to DSM-5 criteria within 6 months before screening

Other illness

• Has had no response (treatment failure) to 2 or more consecutive antidepressant treatments administered at an adequate dose (at or above the minimum therapeutic dose) and duration (at least 6 weeks) in the current episode of depression including the current SSRI/SNRI (ie, the one to be continued in the treatment phases) assessed using the MGH ATRQ.

• Adults aged 18 (or the legal age of consent in the jurisdiction in which the study is taking place) to 64 years, inclusive.
• Be medically stable based on physical examination (including a brief neurologic examination), medical history, vital signs (including blood pressure), and 12-lead ECG performed at screening and OL baseline. If there are any abnormalities that are not specified in the inclusion and exclusion criteria, their significance must be determined by the investigator and recorded in the participant’s source documents and initialed by the investigator.
• Be medically stable based on clinical laboratory tests performed at screening. If the results of the serum chemistry panel, hematology, or urinalysis are outside the normal reference ranges, retesting of an abnormal laboratory value(s) that may lead to exclusion will be allowed once during the screening phase. The participant may be included only if the investigator judges the abnormalities or deviations from normal to be not clinically significant or to be appropriate and reasonable for the population under study. This determination must be recorded in the participant's source documents and initialed by the investigator.
• Meet DSM-5 diagnostic criteria for recurrent or single episode MDD, without psychotic features, based upon clinical assessment and confirmed by the SCID-CT.
• Have symptoms of anhedonia based on clinical assessment and confirmed by presence of anhedonia (positive response to MDE module symptom Item 2) on the SCID-CT and SHAPS total score.