A Trial to Evaluate the Efficacy, Safety & Tolerability of Brexpiprazole in the Maintenance Treatment of Adults With Major Depressive Disorder

Inclusion Criteria:

- Subjects with both a diagnosis of recurrent major depressive disorder, and in a
current major depressive episode of ≥ 8 weeks in duration, as defined by Diagnostic
and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) and confirmed by both
the Mini International Neuropsychiatric Interview (MINI) and an adequate clinical
psychiatric evaluation.

- Subjects must have reported a history for the current major depressive episode of an
inadequate response to 1 or 2 adequate antidepressant treatments, and subjects must
currently be taking a protocol-mandated antidepressant treatment at an adequate dose
and duration, and most not have reported ≥ 50% improvement. For subjects who are
currently on an adequate dose of protocol-mandated antidepressant therapy (ADT), but
for an inadequate duration, can use the screening period to achieve adequate duration.
At Phase A baseline visit, all subjects must have either 2 or 3 documented inadequate
responses to antidepressant treatment in total for the current episode as defined by
the Massachusetts General Hospital Antidepressant Treatment Response Questionnaire
(ATRQ)

- Subjects with a Hamilton Rating Scale for Depression (HAM-D17) total score ≥ 18 at the
screening visit, and Phase A baseline visits.

- Subjects willing to discontinue all prohibited psychotropic medications to meet
protocol-required washouts prior to and during the trial period.

Exclusion Criteria:

- Females who are breast-feeding and/or who have a positive pregnancy test result prior
to receiving investigational medicinal product (IMP).

- Sexually active males or females of childbearing potential who do not agree to
practice 2 different methods of birth control or remain abstinent during the trial and
for 30 days after the last dose of IMP.

- Subjects who report treatment with adjunctive antipsychotic medication with an
antidepressant for a minimum of 3 weeks during the current major depressive episode

- Subjects who report allergies or an intolerability (lifetime treatment history) to
trial-provided ADTs that have not been prescribed to the subject during the current
major depressive episode.

- Subjects who have received ECT for the current major depressive episode

- Subjects who have had an inadequate response to ECT at any time in the past or who
have had a vagus nerve stimulation or deep brain stimulation device implanted at any
time for the management of treatment-resistant depression. Subjects who have had
transcranial magnetic stimulation during the current major depressive episode.

- Subjects with a current need for involuntary commitment or who have been hospitalized
within 4 weeks of screening for the current major depressive episode.

- Subjects with a primary DSM-5 diagnosis of:

1. Schizophrenia Spectrum and Other Psychotic Disorders

2. Bipolar and Related Disorders

3. Obsessive Compulsive Disorders

4. Feeding and Eating Disorders

5. Neurocognitive Disorders

6. Panic Disorder

7. Post-Traumatic Stress Disorder

- Subjects with a current DSM-5 diagnosis of borderline, antisocial, paranoid, schizoid,
schizotypal, or histrionic personality disorder or intellectual disability.

- Subjects experiencing hallucinations, delusions, or any psychotic symptomatology in
the current major depressive episode

- Subjects receiving new onset psychotherapy (individual, group, marriage or family
therapy) within 42 days of screening or at any time during participation in the trial

- Subjects who have met DSM-5 criteria for substance use disorder (moderate or severe)
within the past 60 days; including alcohol and benzodiazepines, but excluding nicotine

- Subjects with hypothyroidism or hyperthyroidism (unless condition has been stabilized
with medications for at least the past 90 days) and/or an abnormal result for free T4
at screening.

- Subjects who currently have clinically significant neurological, hepatic, renal,
metabolic, hematological, immunological, cardiovascular, pulmonary, or
gastrointestinal disorders such as any history of myocardial infarction, congestive
heart failure, HIV seropositive status/acquired immunodeficiency syndrome, chronic
hepatitis B or C.

- Subjects with diabetes mellitus (IDDM and non-IDDM) are ineligible for the trial
unless their condition is stable and well-controlled.

- Subjects with uncontrolled hypertension (DBP > 95 mmHg) or symptomatic hypotension, or
orthostatic hypotension which is defined as a decrease of ≥ 30 mmHg in SBP and/or
decrease of ≥ 20 mmHg in DBP after at least 3 minutes standing compared to the
previous supine blood pressure OR development of symptoms.

- Subjects with known ischemic heart disease or history of myocardial infarction-or
congestive heart failure (whether controlled or uncontrolled)

- Subjects with epilepsy or a history of seizures, except for a single seizure episode

- Subjects with a positive drug screen for cocaine or other drugs of abuse (excluding
known prescription stimulants and other medications and marijuana). Detectable levels
of alcohol, marijuana, barbiturates, or opiates in the drug screen are not
exclusionary if, in the investigator's documented opinion, the subject does not meet
DSM-5 criteria for moderate to severe substance use disorder and the positive test
does not signal a clinical condition that would impact the safety of the subject or
interpretation of the trial results, and participation is agreed to by the medical
monitor prior to treatment.

- Treatment with an MAOI within 14 day prior to the first dose of IMP in Phase A.

- Use of benzodiazepines and/or hypnotics (including non-benzodiazepine sleep aids)
within 7 days prior to first dose of IMP in Phase A.

- Use of varenicline within 5 days prior to the first dose of IMP in Phase A.

- Use of oral (or immediate release intramuscular) neuroleptics within 7 days prior or
long-acting approved neuroleptics ≤ 1 full cycle plus 1/2 cycle prior to the first
dose of IMP in Phase A.

- Subjects who would be likely to require prohibited concomitant therapy during the
trial.

- Subjects who have been exposed to brexpiprazole in any prior clinical trial or has
received commercial brexpiprazole (Rexulti).

- Subjects with a history of neuroleptic malignant syndrome or serotonin syndrome.

- Subjects with a history of true allergic response to more than one class of
medications

- Prisoners or subjects who are compulsorily detained for treatment of either a
psychiatric or physical illness.

- Subjects who participated in any clinical trial within the last 60 days or who
participated in more than 2 clinical trials within the past year