Double-Blind, Placebo-Controlled Trial of Ketamine Therapy in Treatment-Resistant Depression (TRD)

Inclusion Criteria:

   - Male or female, 18-70 years old.

   - Able to read, understand, and provide written, dated informed consent prior to
   screening.

   - Diagnosed with Major Depressive Disorder (MDD), single or recurrent, and currently
   experiencing a Major Depressive Episode (MDE) of at least eight weeks in duration,
   prior to screening.

   - Has a history of TRD during the current MDE.

   - Meet the threshold on the total MADRS score of greater than or equal to 20 at both
   screening and baseline visits (Day -7/-28 and Day 0), as confirmed by the remote
   centralized MGH CTNI rater between the screen visit and the baseline visit.

   - In good general health

   - For female participants, status of non-childbearing potential or use of an acceptable
   form of birth control

   - Body mass index between 18-35 kg/m2

   - Concurrent psychotherapy will be allowed if the type and frequency of the therapy has
   been stable for at least three months prior to screening and is expected to remain
   stable during participation in the study

   - Concurrent hypnotic therapy will be allowed if the therapy has been stable for at
   least 4 weeks prior to screening and if it is expected to remain stable during the
   course of the subject's participation in the study.

Exclusion Criteria:

   - Female of childbearing potential who is not willing to use one of the specified forms
   of birth control during the study

   - Female that is pregnant or breastfeeding

   - Female with a positive pregnancy test at screening or baseline

   - History during the current MDE of failure to achieve a satisfactory response to >7
   treatment courses of a therapeutic dose of an antidepressant therapy of at least 8
   weeks duration during the current episode

   - Total MADRS score of <20 at the screen or baseline visits, or as assessed by the
   remote, independent MGH CTNI rater and reported to the site

   - Current diagnosis of a Substance Use Disorder (Abuse or Dependence) with the exception
   of nicotine dependence, at screening or within 6 months prior to screening

   - Current Axis I disorder that is the principal focus of treatment and MDD the secondary
   focus of treatment for the past 6 months or more

   - History of bipolar disorder, schizophrenia or schizoaffective disorders, or any
   history of psychotic symptoms in the current or previous depressive episodes

   - History of eating disorders within five years of screening

   - Any Axis I or Axis II Disorder, which at screening is clinically predominant to their
   MDD or has been predominant at any time within 6 months prior to screening

   - Subject is considered at significant risk for suicidal behavior during the course of
   their participation in the study

   - Has failed to respond to electroconvulsive therapy (ECT) during the current depressive
   episode

   - Has received vagus nerve stimulation (VNS) at any time prior to screening

   - Has dementia, delirium, amnestic, or any other cognitive disorder

   - Has a clinically significant abnormality on the screening physical examination

   - Participation in any clinical trial with an investigational drug or device within the
   past month or concurrent to study participation

   - Current episode of:

      1. Hypertension, Stage 1 as defined by a systolic blood pressure ≥140mmHg or
      diastolic blood pressure ≥90 mmHg at screening on two of three measurements
      (standing and supine) at least 15 minutes apart.

      2. Hypertension, Stage 1 as defined by a systolic blood pressure ≥155 mmHg or
      diastolic blood pressure ≥99 mmHg at the Baseline Visit (Visit 1) within 1.5
      hours prior to randomization on two of three measurements (standing and supine)
      at least 15 minutes apart.

      3. Recent myocardial infarction (within one year) or a history of myocardial
      infarction.

      4. Syncopal event within the past year.

      5. Congestive heart failure (CHF) New York Heart Association Criteria >Stage 2

      6. Angina pectoris.

      7. Heart rate <50 or >105 beats per minute at screening or randomization (Baseline
      Visit).

      8. QTcF (Fridericia-corrected) ≥450 msec at screening or randomization (Baseline
      Visit).

   - Current history of hypertension, or on antihypertensives for the purpose of lowering
   blood pressure, who have either had an increase in antihypertensive dose or increase
   in the number of antihypertensive drugs used to treat hypertension over the last 2
   months.

   - Chronic lung disease excluding asthma.

   - Lifetime history of surgical procedures involving the brain or meninges, encephalitis,
   meningitis, degenerative central nervous system disorder, epilepsy, mental
   retardation, or any other disease/procedure/accident/intervention associated with
   significant injury to or malfunction of the central nervous system, or a history of
   significant head trauma within the past 2 years

   - Presents with any of the following lab abnormalities:

      1. Thyroid stimulating hormone outside of the normal limits and clinically
      significant as determined by the investigator. Free thyroxine (T4) levels may be
      measured if TSH level is high. Subject will be excluded if T4 level is clinically
      significant.

      2. Patients with diabetes mellitus fulfilling any of the following criteria:

   i. Unstable diabetes mellitus defined as glycosylated hemoglobin (HbA1c) >8.5% at
   screening ii. Admitted to hospital for treatment of diabetes mellitus or diabetes
   mellitus related illness in the past 12 weeks iii. Not under physician care for
   diabetes mellitus iv. Has not been on the same dose of oral hypoglycaemic drug(s)
   and/or diet for the 4 weeks prior to screening. For thiazolidinediones (glitazones)
   this period should not be less than 8 weeks.

   c. Any other clinically significant abnormal laboratory result (as determined after
   evaluation by study investigator and MGH CTNI medical monitor) at the time of the
   screening exam.

   - History of hypothyroidism and has been on a stable dosage of thyroid replacement
   medication for less than 2 months prior to screening. (Subjects on a stable dosage of
   thyroid replacement medication for at least 2 months or more prior to screening are
   eligible for enrollment.)

   - History of hyperthyroidism which was treated (medically or surgically) less than six
   months prior to screening

   - Any current or past history of any physical condition which in the investigator's
   opinion might put the subject at risk or interfere with study results interpretation

   - History of positive screening urine test for drugs of abuse at screening

   - Patients with exclusionary laboratory values, or requiring treatment with exclusionary
   concomitant medications

   - Patients on exclusionary concomitant psychotropic medications, the half-life of which
   would not allow sufficient time for patients to have been free of the medication
   post-taper for five half-lives within the maximum screening period (28 days).

   - Patient who have participated in studies of ketamine or AZD6765 or other NMDA receptor
   antagonists for depression and received active treatment.

   - Patients with narrow angle glaucoma

   - Patients with a lifetime history of PCP/Ketamine drug use

   - Liver Function Tests higher than 2.5 times upper limit of normal