A Study of Esketamine Nasal Spray Plus a New Standard-of-care Oral Antidepressant or Placebo Nasal Spray Plus a New Standard-of-care Oral Antidepressant in Adult and Elderly Participants With Treatment-resistant Depression

Percentage of participants with remission (as assessed by MADRS [total score of <= 10) at Week 8 without relapse until Week 32 will be reported at Week 32. A relapse is defined any of following- a) Worsening of depressive symptoms in participants who have achieved remission, as indicated by MADRS total score greater than equal to (>=) 22 confirmed by one additional assessment of MADRS total score >= 22 within next 5 to 15 days (until Week 32). Date of second MADRS assessment will be used for date of relapse; b) Any psychiatric hospitalization for worsening of depression, hospitalization for suicide prevention or completed suicide. For any of these events, start date of hospitalization will be used for date of relapse, c) Suicide attempt or any other clinically relevant event determined per the investigator's clinical judgment to be indicative of a relapse of depressive illness, but for which participant was not hospitalized. The onset of event will be used for date of relapse.

The MADRS is a clinician-rated scale designed to measure depression severity. The scale consists of 10 items, each of which is scored from 0 (item not present or normal) to 6 (severe or continuous presence of the symptoms). These item scores are summed up to yield a total score. The range of the total score is 0 to 60. Higher scores represent a more severe condition. The MADRS evaluates apparent sadness, reported sadness, inner tension, sleep, appetite, concentration, lassitude, inability to feel (interest level), pessimistic thoughts, and suicidal thoughts.

The MADRS is a clinician-rated scale designed to measure depression severity. The scale consists of 10 items, each of which is scored from 0 (item not present or normal) to 6 (severe or continuous presence of the symptoms). These item scores are summed up to yield a total score. The range of the total score is 0 to 60. Higher scores represent a more severe condition. The MADRS evaluates apparent sadness, reported sadness, inner tension, sleep, appetite, concentration, lassitude, inability to feel (interest level), pessimistic thoughts, and suicidal thoughts.

The PHQ-9 is a 9-item, patient-reported outcome (PRO) measure to assess depressive symptoms. The scale scores each of the 9-symptom domains of the Diagnostic and Statistical Manual of Mental Disorders, fifth edition major depressive disorder (DSM-5 MDD) criteria. Each item is rated on a 4 point scale (0=not at all, 1=several days, 2=more than half the days, and 3=nearly every day). The participant's item responses are summed to provide a total score (range of 0 to 27), with higher scores indicating greater severity of depressive symptoms.

The CGI-S rating scale is a global assessment that measures the clinician's impression of the severity of illness of the participant. A rating scale of 1 to 7 is used, with 1="normal, not at all ill" and 7="among the most extremely ill".

The CGI-C rating scale is a global assessment that measures the clinician's impression illness change. CGI-C scores range from 1 (very much improved) through to 7 (very much worse).

The SDS, a patient-reported outcome measure, is a 5-item questionnaire that has been widely used and accepted for assessment of functional impairment and associated disability. The first 3 items cover (1) work/school, (2) social life, and (3) family life/home responsibilities using a rating scale from 0 to 10. The score for the first 3 items are summed to create a total score of 0 to 30, where higher score indicates greater impairment.

The Short-Form-36 (SF-36) is a 36-item questionnaire which measures quality of life (QoL) across 8 domains, which are both physically and emotionally based. The 8 domains that the SF36 measures are as follows: physical functioning; role limitations due to physical health; role limitations due to emotional problems; energy/fatigue; emotional wellbeing; social functioning; pain; general health. For each of the 8 domains that the SF-36 measures, an aggregate score is produced. The scores range from 0 (lowest or worst possible level of functioning) to 100 (highest or best possible level of functioning).

The QLDS is a disease specific PRO designed to assess health related quality of life in patients with Major Depressive Disorder. The instrument has a recall period of "at the moment", contains 34-items with "yes"/"no" response options and takes approximately 5-10 minutes to complete. The total score is computed as sum of the items with range from 0 (good quality of life) to 34 (very poor quality of life).

The EQ-5D-5L is standardized instrument for use as measure of health outcome, primarily designed for self-completion by respondents. It consists of EQ-5D-5L descriptive system and EQ-VAS. The EQ-VAS rating "health today" with range from 0 (worst imaginable health state) to 100 (best imaginable health state).

The EQ-5D-5L is standardized instrument for use as measure of health outcome, primarily designed for self-completion by respondents. It consists of EQ-5D-5L descriptive system and EQ-VAS. EQ-5D-5L descriptive system comprises the following 5 dimensions: Mobility, self-care, usual activities, pain/discomfort and anxiety/depression. Each of 5 dimensions is divided into 5 levels of perceived problems (1 indicating no problem, 2 indicating slight problems, 3 indicating moderate problems, 4 indicating severe problems, 5 indicating extreme problems). Participant selects an answer for each of 5 dimensions considering the response that best matches his or her health "today". The responses to the 5 dimensions are used to compute a single score ranging from zero (0.0- worst health state) to 1 (1.0- better health state) representing the general health status of the individual.

WPAI-SHP is a validated short instrument that assesses impairment in work and other regular activities over the past 7 days. WPAI produces four types of scores: absenteeism (work time missed), presenteeism (impairment at work/reduced on-the-job effectiveness), work productivity loss (overall work impairment/absenteeism plus presenteeism), and activity impairment. The WPAI outcomes are expressed as impairment percentages, with higher numbers indicating greater impairment and less productivity, that is, worse outcomes.

Number of medical care encounters and treatments (including physician or emergency room visits, tests and procedures, and medications, and other procedures) will be reported.

An adverse event (AE) is any untoward medical occurrence attributed to study drug in a participant who received study drug.

Suicidal ideation or behavior will be measured using C-SSRS score. C-SSRS is a clinician rated assessment of suicidal behavior and/ or intent. Scale consists of 28 items in 4 sections: suicide behavior, actual attempts, suicidal ideation, and intensity of ideation. Suicidal ideation consists of 5 yes/no items: wish to be dead, non-specific active suicidal thoughts, active suicidal ideation with any methods (not plan) without intention to act, active suicidal ideation with some intent to act without specific plan, active suicidal ideation with specific plan and intent. Worsening of suicidal ideation will be an increase in severity of suicidal ideation from baseline.