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

The purpose of this study is to evaluate the efficacy of treating participants with treatment-resistant depression (TRD) who have failed at least 2 (and no more than 6) prior antidepressant (AD) treatments in the current moderate to severe depressive episode with flexibly-dosed esketamine nasal spray plus a newly initiated oral standard-of-care AD compared with placebo nasal spray plus a newly-initiated standard-of-care oral AD, in achieving remission and staying relapse-free after remission.