A Study to Evaluate ALKS 5461 in Subjects With Major Depressive Disorder (MDD)

Inclusion Criteria: * Diagnosed with a major depressive episode (MDE) * Body mass index less than or equal to 40 kg/m2 * Have been treated with an adequate dose of SSRI/SNRI during the current MDE for at least 8 weeks, with the same, adequate dose over the last 4 weeks that is expected to remain stable throughout the study * History of inadequate response during the entire current MDE to 1 or 2 adequate antidepressant treatments, including current treatment * Be otherwise physically healthy Exclusion Criteria: * Have an axis I diagnosis of delirium, dementia, amnestic or other cognitive disorder, schizophrenia or other psychotic disorder, bipolar I or II disorder, eating disorder, obsessive-compulsive disorder, panic disorder, acute stress disorder, or posttraumatic stress disorder * Have a clinically significant current axis II diagnosis of borderline, antisocial, paranoid, schizoid, schizotypal, or histrionic personality disorder * Are experiencing hallucinations, delusions, or any psychotic symptomatology in the current MDE * Receive new onset psychotherapy within 6 weeks of screening * Use of opioid agonists (eg, codeine, oxycodone, morphine) within 14 days before screening * Have received electroconvulsive therapy during the current MDE * Have attempted suicide within the past 2 years * Have a thyroid pathology * Have a history of a seizure disorder or of neuroleptic malignant syndrome/serotonin syndrome * Have a positive test for human immunodeficiency virus (HIV) Additional inclusion/exclusion criteria may apply