Intervention: Ketamine
Trial phase: Phase 3
ATC code: N01AX03 | N01AX14 | N06AX27
SMILES: CNC1(c2ccccc2Cl)CCCCC1=O
Sex: All
Age groups: Adult
Healthy volunteers: No
Participants at risk: 113
Group description: Subjects self-administered esketamine 84 milligram (mg) intranasally (1 spray of esketamine 14 mg to each nostril at 0, 5 and 10 minutes) twice per week for 4 weeks (Days 1, 4, 8, 11, 15, 18, 22, and 25) plus received SOC antidepressant treatment which was initiated or optimized on Day 1 during double blind phase.
Eligibility criteria:
Inclusion Criteria:

Participant must meet Diagnostic and Statistical Manual of Mental Disorders (5th edition) (DSM-5) diagnostic criteria for Major Depressive Disorder (MDD), without psychotic features, based upon clinical assessment and confirmed by the Mini International Psychiatric Interview (MINI)
In the physician's opinion, acute psychiatric hospitalization is clinically warranted due to participant's imminent risk of suicide
Participants must have current suicidal ideation with intent, confirmed by a "Yes" response to Question B3 [Think (even momentarily) about harming or of hurting or of injuring yourself: with at least some intent or awareness that you might die as a result; or think about suicide (ie, about killing yourself)?] and Question B10 [Intend to act on thoughts of killing yourself?] obtained from the MINI. Note: the response to B3 must refer to the present, whereas the response to B10 may reflect the past 24 hours. If the screening period is longer than 24 hours, assessment of B3 and B10 of MINI must be repeated prior to randomization to confirm eligibility
Participant has a Montgomery Asberg Depression Rating Scale (MADRS) total score of greater than (>) 28 predose on Day 1
As part of standard of care treatment, participant agrees to be hospitalized voluntarily for a recommended period of 5 days after randomization (may be shorter or longer if clinically warranted in the investigator's opinion) and take prescribed non-investigational antidepressant therapy(ies) for at least the duration of the double-blind treatment phase (Day 25)
Participant is comfortable with self-administration of intranasal medication and able to follow instructions provided

Exclusion Criteria:

Participant has a current DSM-5 diagnosis of bipolar (or related disorders), antisocial personality disorder, or obsessive compulsive disorder
Participant currently meets DSM-5 criteria for borderline personality disorder. Participant not meeting full DSM-5 criteria for borderline personality disorder but exhibiting recurrent suicidal gestures, threats, or self-mutilating behaviors should also be excluded
Participant has a current clinical diagnosis of autism, dementia, or intellectual disability
Participant has a current or prior DSM-5 diagnosis of a psychotic disorder, or MDD with psychotic features
Participant meets the DSM-5 severity criteria for moderate or severe substance or alcohol use disorder, (except for nicotine or caffeine), within the 6 months before screening. A history (lifetime) of ketamine, phencyclidine (PCP), lysergic acid diethylamide (LSD), or 3, 4-methylenedioxy-methamphetamine (MDMA) hallucinogen-related use disorder is exclusionary