['major depressive disorder']
['nrx-1074 1 mg', 'placebo', 'nrx-1074 5 mg', 'nrx-1074 10 mg']

        Inclusion Criteria:

          -  Male and female subjects

          -  Aged 18 to 65 years

          -  Meets Diagnostic and Statistical Manual, Fourth Edition, Text Revision (DSM-IV-TR)
             criteria for major depressive disorder (MDD)

          -  Current episode has lasted ≥ 8 weeks before Screening

          -  HDRS-17 score ≥ 21 before beginning the washout of all current antidepressant agents
             and/or adjuvant agents

          -  HDRS-17 score ≥ 21 at Baseline (after 14 days of washout of current antidepressant
             agents)

          -  Female subjects of childbearing potential with a negative serum pregnancy test prior
             to entry into the study and who are practicing an adequate method of birth control (eg
             oral or parenteral contraceptives, intrauterine device, barrier, abstinence) and who
             do not plan to become pregnant during the course of the study. Female subjects may be
             included without a negative serum pregnancy test if they are surgically sterile or at
             least 2 years post-menopausal

          -  Male subjects and their female sexual partner should use an acceptable method of birth
             control during the study

          -  Clinical laboratory values < 2 times the upper limit of normal (ULN) or deemed not
             clinically significant per the investigator and Naurex medical monitor

          -  Ability to understand the requirements of the study, provide written informed consent,
             abide by the study restrictions, and agree to return for the required assessments

          -  Based on both the investigator and Naurex medical monitor's clinical judgment,
             subjects with eating disorders, obsessive compulsive disorder (OCD), panic disorder,
             post-traumatic stress disorder (PTSD), and generalized anxiety disorders secondary to
             major depressive episodes are permitted

        Exclusion Criteria:

          -  Axis I diagnosis of delirium, dementia, dysthymia, amnestic or other cognitive
             disorder, schizophrenia or other psychotic disorder, bipolar I or II disorder, eating
             disorder (anorexia or bulimia nervosa), obsessive-compulsive disorder, panic disorder,
             agoraphobia, social phobia, attention-deficit hyperactivity disorder (ADHD), or PTSD

          -  A clinically significant current Axis II diagnosis of borderline, antisocial,
             paranoid, schizoid, schizotypal, or histrionic personality disorder

          -  Experiencing hallucinations, delusions, or any psychotic symptomatology in the current
             episode; lifetime history of psychosis

          -  Huntington's, Parkinson's, Alzheimer's, Multiple Sclerosis, or a history of seizures
             or strokes

          -  Currently hospitalized or residing in an in-patient facility during the study
             participation

          -  Substance abuse within the last 12 months, including greater than or equal to 5 units
             of alcohol per day where 1 unit = 1/2 pint of beer, 1 glass of wine, or 1 oz. of
             spirits consumed most weeks or in the opinion of the investigator

          -  Allergy or intolerance to current antidepressant or other current medications

          -  Participation in any clinical trial of an investigational product or device within 30
             days of enrollment in this trial

          -  Positive screen for drugs of abuse: cocaine, marijuana, PCP, ketamine, opioid or other
             agent that in the opinion of the investigator is being abused

          -  Have received electroconvulsive therapy, transcranial magnetic stimulation (TMS), or
             vagal nerve stimulation (VNS) for the current depressive episode

          -  Post current (past 6 months) suicide risk based on administration of the C-SSRS and
             the investigator's clinical judgment

          -  Human immunodeficiency virus (HIV) infection (based on the HIV-1 & HIV-2 antibody
             screen) or other ongoing infectious disease

          -  Females or female partners of male subjects who are currently pregnant or planning to
             become pregnant during the course of the study. Women who are breastfeeding

          -  Currently taking prescription (psychiatric treatments, antidepressant treatments) or
             over-the-counter medications including herbal therapies to treat their MDD or
             conditions secondary to their period following study drug dosing. Dextromethorphan or
             tramadol since these are serotonin uptake inhibitors.
      