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

All participants will start with first dose (Day 1 as 28 milligram \[mg\]); second dose (Day 4) is either 28 or 56 mg. All subsequent doses may be 28, 56 or 84 mg. After the first dose, all dosing decisions are determined by the investigator based on efficacy and tolerability.

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 given at a dose of 10 mg/day throughout the Double-Blind Induction Phase. This dose (10 mg/day) is the also the minimum therapeutic dose.

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 may be titrated up to 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 may be titrated up to a dose of 150 mg/day, but if not tolerated the dose can be reduced to the minimum therapeutic dose of 75 mg/day.