A Study to Evaluate the Safety and Efficacy of Intranasal Esketamine in Treatment-resistant Depression

This will be a 2-panel, randomized ( participants are assigned different treatments based on chance), double-blind (neither investigator nor participant knows which treatment the participant receives), placebo-controlled (placebo is an inactive substance that is compared with a drug to test whether the drug has a real effect in a clinical trial), multicenter study. Approximately 100 male and female adult participants diagnosed with TRD will participate in this study. For participants in both panels (Panel A and Panel B), there will be 4 study phases: a 4-week screening phase, a double-blind treatment phase (Day 1 to Day 15), an optional open-label treatment phase (Panel A: Day 15 to 74; Panel B: Day 15 to 25), and an 8-week post-treatment (follow-up) phase. Depending on the treatment Panel, patients will be assigned to intranasal placebo or intranasal esketamine 14 mg, 28 mg, 56 mg, or 84 mg. Safety assessments will be performed throughout the study. The maximum study duration for a participant will be 23 weeks for Panel A and 16 weeks for Panel B.