Approximately 56 participants will be randomized in a total of 20-25 centers worldwide. The trial consists of screening period of up to 28 days. On Day 1, eligible participants will be randomized to one of the treatment arms (low, medium or high dose of MIJ821) or placebo and receive study treatment administered as a single subcutaneous injection. Participant will remain at the clinic for at least 4 hours after administration of study treatment for safety observation including assessment of local tolerability by visual inspection of the injection area. Post-dose clinic visits will occur 24 hours post dose (Day 2), Days 8, 15, 22 and 29 to evaluate efficacy and safety. Efficacy assessments will include the Montgomery-Asberg Depression Scale (MADRS) and other clinical outcome assessments (COAs). Safety assessments include laboratory tests, ECGs, vital signs and physical examinations. In addition phone calls will be conducted 3 days after each on-site clinic visit with the exception of End-of-study (EOS) visit. EOS visit will be completed on site on Day 29. The total duration of the study is approximately 8 weeks (56 days), including screening.
The main purpose of this study is to evaluate safety and efficacy of a single injection of MIJ821 in addition to standard of care (SoC) pharmacological anti-depressant treatment in participants with treatment-resistant depression (TRD)