Study of Lurasidone as Adjunctive Treatment in Patients With Major Depressive Disorder With Inadequate Response to Antidepressant Monotherapy

This Phase 3, multicenter, randomized, double-blind, placebo-controlled clinical trial is designed to evaluate the efficacy and safety of lurasidone as adjunctive therapy in adult patients with major depressive disorder (MDD) who show an inadequate response to antidepressant monotherapy. Eligible participants will continue their background antidepressant treatment and be randomized to receive either lurasidone (20, 40, or 60 mg/day) or placebo for 8 weeks. The primary endpoint is the change from baseline in the Montgomery-Åsberg Depression Rating Scale (MADRS) total score at Week 8. Secondary endpoints include response and remission rates, changes in Clinical Global Impression-Severity (CGI-S), 17-item Hamilton Depression Rating Scale (HAM-D17), Hamilton Anxiety Rating Scale (HAM-A), and Sheehan Disability Scale (SDS) scores. Safety assessments will include adverse events, laboratory tests, electrocardiograms (ECGs), vital signs, and suicidality monitoring Columbia-Suicide Severity Rating Scale (C-SSRS).

Inclusion Criteria: * Signed informed consent prior to participation * Outpatients aged 19-65 years * Diagnosis of Major Depressive Disorder (MDD) per DSM-5 using MINI; psychotic features allowed * Current major depressive episode lasting ≥8 weeks at baseline * MADRS total score ≥24 at both screening and baseline * CGI-S score ≥4 at both screening and baseline * Documented history of antidepressant treatment (ADT) with inadequate response (\2× ULN, bilirubin \>1.5× ULN, Hb \