Time to relapse was defined as days from the first dose of the study drug in the DB Phase to the day of relapse during the DB Phase. Participant was considered to have relapsed if: 2 consecutive HAM-D scores were ≥ 18 assessed 7 to 14 days apart, any worsening of depression requiring hospitalization, Investigator-determined risk of suicide, or any other clinically relevant event whether or not hospitalization was required. HAM-D is a scale used to rate depression in participants who were already diagnosed as depressed. The HAM-D total score comprised a sum of 17 individual item scores. Items scored in a range of 0 to 2 included: insomnia, somatic symptoms, genital symptoms, loss of weight, and insight. Items scored in a range of 0 to 4 included: agitation, depressed mood, feelings of guilt, suicide, work and activities, retardation, anxiety, hypochondriasis. The HAM-D total score could range from 0 (not depressed) to 52 (severely depressed). Higher scores indicated more depression.

Due to early termination of the study by the sponsor, no data was collected, and no efficacy analysis was performed as planned, thus data is not available for this outcome measure.

Participant was considered to have relapsed if: 2 consecutive HAM-D scores were ≥ 18 assessed 7 to 14 days apart, worsening of depression requiring hospitalization, Investigator-determined risk of suicide, or other clinically relevant events whether hospitalization was required. HAM-D scale was used to rate depression in participants who were diagnosed as depressed. Total score is a sum of 17 individual item scores. Items in a range of 0-2 included: insomnia (early, middle, late), somatic symptoms (gastrointestinal and general), genital symptoms, loss of weight, and insight. Items in a range of 0-4 included: agitation, depressed mood (sadness, hopeless, helpless, worthless), feelings of guilt, suicide, work and activities, retardation (slowness of thought and speech; impaired ability to concentrate; decreased motor activity), anxiety (psychic and somatic), hypochondriasis. Total score could range from 0 (not depressed)- 52 (severely depressed). Higher scores indicated more depression.

Due to early termination of the study by the sponsor, no data was collected, and no efficacy analysis was performed as planned, thus data is not available for this outcome measure.

The 17-item HAM-D scale was used to rate the severity of depression in participants who were already diagnosed as depressed. The HAM-D total score comprised a sum of 17 individual item scores. Items scored in a range of 0 to 2 included: insomnia (early, middle, late), somatic symptoms (gastrointestinal and general), genital symptoms, loss of weight, and insight. Items scored in a range of 0 to 4 included: agitation, depressed mood (sadness, hopeless, helpless, worthless), feelings of guilt, suicide, work and activities, retardation (slowness of thought and speech; impaired ability to concentrate; decreased motor activity), anxiety (psychic and somatic), hypochondriasis. The HAM-D total score could range from 0 (not depressed) to 52 (severely depressed). Higher scores indicated more depression. A negative change from baseline indicated improvement.

Due to early termination of the study by the sponsor, no data was collected, and no efficacy analysis was performed as planned, thus data is not available for this outcome measure.

HAM-D response was defined as having a 50% or greater reduction from baseline in HAM-D total score. The HAM-D total score comprised a sum of 17 individual item scores. Items scored in a range of 0 to 2 included: insomnia (early, middle, late), somatic symptoms (gastrointestinal and general), genital symptoms, loss of weight, and insight. Items scored in a range of 0 to 4 included: agitation, depressed mood (sadness, hopeless, helpless, worthless), feelings of guilt, suicide, work and activities, retardation (slowness of thought and speech; impaired ability to concentrate; decreased motor activity), anxiety (psychic and somatic), hypochondriasis. The HAM-D total score could range from 0 (not depressed) to 52 (severely depressed). Higher scores indicated more depression.

Due to early termination of the study by the sponsor, no data was collected, and no efficacy analysis was performed as planned, thus data is not available for this outcome measure.

HAM-D remission was defined as having a HAM-D total score of ≤ 7. The HAM-D total score comprised a sum of 17 individual item scores. Items scored in a range of 0 to 2 included: insomnia (early, middle, late), somatic symptoms (gastrointestinal and general), genital symptoms, loss of weight, and insight. Items scored in a range of 0 to 4 included: agitation, depressed mood (sadness, hopeless, helpless, worthless), feelings of guilt, suicide, work and activities, retardation (slowness of thought and speech; impaired ability to concentrate; decreased motor activity), anxiety (psychic and somatic), hypochondriasis. The HAM-D total score could range from 0 (not depressed) to 52 (severely depressed). Higher scores indicated more depression.

Due to early termination of the study by the sponsor, no data was collected, and no efficacy analysis was performed as planned, thus data is not available for this outcome measure.

The CGI-I employs a 7-point Likert scale to measure the overall improvement in the participant's condition posttreatment. The Investigator rated the participant's total improvement whether or not it was due entirely to drug treatment. Response choices included: 1=very much improved, 2=much improved, 3=minimally improved, 4=no change, 5=minimally worse, 6=much worse, and 7=very much worse. The CGI-I is only rated at posttreatment assessments. By definition, all CGI-I assessments are evaluated against baseline conditions. Higher score indicated worse condition. CGI-I response was defined as having a CGI-I score of "very much improved" or "much improved."

Due to early termination of the study by the sponsor, no data was collected, and no efficacy analysis was performed as planned, thus data is not available for this outcome measure.

The CGI-S uses a 7-point Likert scale to rate the severity of the participant's illness at the time of assessment, relative to the clinician's past experience with participants who had the same diagnosis. Considering total clinical experience, a participant was assessed on severity of mental illness at the time of rating as 1=normal, not at all ill; 2=borderline mentally ill; 3=mildly ill; 4=moderately ill; 5=markedly ill; 6=severely ill; and 7= among the most extremely ill participant. A higher score indicated extreme illness. A negative change from baseline indicated improvement (a higher absolute number indicating more illness).

Due to early termination of the study by the sponsor, no data was collected, and no efficacy analysis was performed as planned, thus data is not available for this outcome measure.

The PHQ-9 is a participant-rated depressive symptom severity scale. To monitor severity over time participants in current treatment for depression, participants completed the questionnaires at baseline and at regular intervals thereafter. Scoring was based on responses to specific questions, as follows: 0=not at all; 1=several days; 2=more than half the days; and 3=nearly every day. The PHQ-9 total score was calculated as the sum of the 9 individual item scores and ranged from 0 to 27. The PHQ-9 total score was categorized as follows: 1 to 4=minimal depression, 5 to 9=mild depression, 10 to 14=moderate depression, 15 to 19=moderately severe depression; and 20 to 27=severe depression. Higher score indicated severe depression. A negative change from baseline indicated improvement.

Due to early termination of the study by the sponsor, no data was collected, and no efficacy analysis was performed as planned, thus data is not available for this outcome measure.

Time to relapse was defined as days from the first dose of the study drug in the DB Phase to the day of relapse during the DB Phase. Participant was considered to have relapsed if: 2 consecutive HAM-D scores were ≥18 assessed 7 to 14 days apart, any worsening of depression requiring hospitalization, Investigator-determined risk of suicide, or any other clinically relevant event whether or not hospitalization was required. HAM-D is a scale used to rate depression in participants who were already diagnosed as depressed. The HAM-D total score comprised a sum of 17 individual item scores. Items scored in a range of 0 to 2 included: insomnia, somatic symptoms, genital symptoms, loss of weight, and insight. Items scored in a range of 0 to 4 included: agitation, depressed mood, feelings of guilt, suicide, work and activities, retardation, anxiety, hypochondriasis. The HAM-D total score could range from 0 (not depressed) to 52 (severely depressed). Higher scores indicated more depression.

Due to early termination of the study by the sponsor, no data was collected, and no efficacy analysis was performed as planned, thus data is not available for this outcome measure.

An adverse event (AE) was defined as any untoward medical occurrence in a participant or clinical investigation participant administered a pharmaceutical product and that does not necessarily have a causal relationship with this treatment. A TEAE was defined as an AE with onset after the start of study drug, or any worsening of a pre-existing medical condition/AE with onset after the start of study drug and throughout the study.

Safety Set included all participants who were administered the study drug. Data for this outcome measure was not collected for DB Phase: Placebo arm because none of the participants were enrolled into this group.