The primary objective is to evaluate the efficacy of Ropanicant at two different dosage levels compared to placebo in patients with Major Depressive Disorder (MDD).

This is a Phase 2b, randomized, double-blind, placebo-controlled, parallel-group, multicenter trial to evaluate the efficacy and safety of Ropanicant versus placebo in patients with MDD. The study will be conducted at multiple centers located in the US.

This study consists of a 4-weeks screening period, 6-weeks treatment period, and a 2-weeks follow-up period. Approximately 195 patients will be randomly assigned to receive Ropanicant Dose Level 1 bid or Dose Level 2 bid, or placebo bid for 6 weeks in a ratio of 1:1:1 (65 patients in each treatment group).

Inclusion Criteria:

• Patients must meet the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR) criteria for MDD without psychotic features based on the Mini International Neuropsychiatric Interview (MINI) with a current major depressive episode of at least 4 weeks of duration but no longer than 12 months.
• Patients must have a Clinical Global Impression-Severity (CGI-S) score of ≥4.
• Patients must have a Structured Interview Guide for the Hamilton Depression Rating Scale (SIGH-D) score of ≥20.
• Patients must have a Snaith-Hamilton Pleasure Scale (SHAPS) score of ≥20.
• Patients must have vision and hearing (corrected if needed) sufficient to comply with the testing procedures.

Exclusion Criteria:

• Patients who meet criteria for treatment-resistant depression (TRD) during the current major depressive episode, which is defined as being nonresponders (<50% of symptom improvement) to 2 or more depression treatment periods of adequate dose and duration.
• Patients not in good general health with clinically significant abnormalities as assessed by the investigator and determined by physical examination results, neurological examination results, ECG results, or laboratory assessments.
• Female patients who are pregnant, planning to become pregnant during the study or within 30 days after the last administration of study drug, or breastfeeding.
• Patients with bradycardia (<50 bpm) or tachycardia (>100 bpm) on the ECG results.