A Study of Intranasal Esketamine Plus an Oral Antidepressant for Relapse Prevention in Adult Participants With Treatment-resistant Depression

This is a randomized, double-blind (neither the researchers nor the participant know what treatment the participants is receiving), active-controlled, multicenter (more than 1 study site) study in participants with TRD to assess the efficacy of intranasal esketamine plus an oral antidepressant compared with an oral antidepressant (active comparator) plus intranasal placebo in delaying relapse of depressive symptoms. The study will consist of 5 phases: Screening/Prospective Observational Phase (4-7weeks) for direct-entry participants only, Open-label Induction Phase (4-weeks) for direct-entry participants only, Optimization Phase (12-weeks; open-label for direct-entry participants and double-blind for transferred-entry participants), Maintenance Phase (variable duration; double-blind for all participants) and Follow-up Phase (2-weeks). Participants' safety will be monitored throughout the study.