A Study of Brexpiprazole Plus Ketamine in Treatment-Resistant Depression (TRD)

Inclusion Criteria

• Male or female, 18 to 65 years of age, inclusive, at screening.
• Able to read, understand, and provide written, dated informed consent prior to screening. Participants will be deemed likely to comply with study protocol and communicate with study personnel about adverse events and other clinically important information.
• Diagnosed with MDD, single or recurrent, and currently experiencing a major depressive episode (MDE) of at least eight weeks in duration, prior to screening, according to the criteria defined in the Diagnosis and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). The diagnosis of MDD will be made by a site psychiatrist and supported by the SCID-5. The diagnosis will be confirmed by remote, independent raters from the MGH CTNI (Massachusetts General Hospital Clinical Trials Network and Institute) with a SAFER interview.
• Has a history of treatment resistant depression (TRD) during the current MDE, as assessed by the investigator and remote centralized rater using the MGH ATRQ. TRD is defined as failure to achieve a satisfactory response (e.g., less than 50% improvement of depression symptoms), as perceived by the participant, to at least 2 "treatment courses" during the current episode of a therapeutic dose of an antidepressant therapy (ADT) of at least 8 weeks duration (including the current ADT). The adequacy of dose and duration of the antidepressant therapy will be determined as per the MGH ATRQ criteria. The TRD status will be confirmed by remote, independent raters from the MGH CTNI who will administer the MGH ATRQ, via teleconference, between the screening visit and the baseline visit. Participants must currently be on a stable (for at least 4 weeks) and adequate (according to the MGH ATRQ) dose of ongoing antidepressant therapy (any antidepressant therapy, with the exception of MAOIs), of which total duration must be at least 8 weeks.
• Meet the threshold on the total MADRS score of >20 at both the screen visit and the baseline visit (Day -7/-28 and Day 0), and as confirmed by the remote centralized MGH CTNI rater between the screen visit and the baseline visit.
• In good general health, as ascertained by medical history, physical examination (PE) (including measurement of supine and standing vital signs), clinical laboratory evaluations, and ECG.
• If female, a status of non-childbearing potential or use of an acceptable form of birth control per the following specific criteria:
• Non-childbearing potential (e.g., physiologically incapable of becoming pregnant, i.e., permanently sterilized (status post hysterectomy, bilateral tubal ligation), or is post-menopausal with her last menses at least one year prior to screening); or
• Childbearing potential, and meets the following criteria:
• Childbearing potential, including women using any form of hormonal birth control, on hormone replacement therapy started prior to 12 months of amenorrhea, using an intrauterine device (IUD), having a monogamous relationship with a partner who has had a vasectomy, or is sexually abstinent.
• Negative urinary pregnancy test at screening, confirmed by a negative urinary pregnancy test at randomization prior to receiving study treatment.
• Willing and able to continuously use one of the following methods of birth control during the course of the study, defined as those which result in a low failure rate (i.e., less than 1% per year) when used consistently and correctly: implants, injectable or patch hormonal contraception, oral contraceptives, IUD, double-barrier contraception, sexual abstinence. The form of birth control will be documented at screening and baseline.
• Body mass index between 18-35 kg/m2.
• Concurrent psychotherapy will be allowed if the type (e.g., supportive, cognitive behavioral, insight-oriented, et al.) and frequency (e.g., weekly or monthly) of the therapy has been stable for at least three months prior to screening and if the type and frequency of the