A Study to Evaluate the Efficacy, Safety, and Tolerability of Flexible Doses of Intranasal Esketamine Plus an Oral Antidepressant in Adult Participants With Treatment-resistant Depression

Participants will self-administer either 56 mg or 84 mg of esketamine, intranasally, twice per week as a flexible dose regimen in the Double-Blind Induction Phase.

Participants will self-administer matching placebo, intranasally, twice per week for 4 weeks as a flexible dose regimen in the Double-Blind Induction Phase.

Duloxetine could be selected as the oral antidepressant medication by the investigator based on review of Massachusetts General Hospital - Antidepressant Treatment Response Questionnaire (MGH-ATRQ) and relevant prior antidepressant medication information. The minimum therapeutic dose is 60 milligram per day (mg/day).

Escitalopram could be selected as the oral antidepressant medication by the investigator based on review of MGH-ATRQ and relevant prior antidepressant medication information. Escitalopram will be titrated upto a dose of 20 mg/day, but if not tolerated the dose can be reduced to the minimum therapeutic dose of 10 mg/day.

Sertraline could be selected as the oral antidepressant medication by the investigator based on review of MGH-ATRQ and relevant prior antidepressant medication information. Sertraline will be titrated upto a dose of 150 mg/day, but if not tolerated the dose can be reduced to the minimum therapeutic dose of 50 mg/day.

Venlafaxine Extended Release could be selected as the oral antidepressant medication by the investigator based on review of MGH-ATRQ and relevant prior antidepressant medication information. Venlafaxine Extended Release will be titrated upto a dose of 225 mg/day, but if not tolerated the dose can be reduced to the minimum therapeutic dose of 150 mg/day.