• The primary efficacy measure is the Montgomery-Asberg Depression Rating Scale (MADRS). [ Time Frame: Weekly and bi-weekly assessments ] [ Designated as safety issue: No ]
  

• Efficacy measures: IDS-SR 30, HADS, CGI-I and CGI-S; Safety measures: PE, clinical laboratory evaluations, 12-lead ECG, AEs, vital signs, and suicidality assessment using the Columbia Suicide Severity Rating Scale (C-SSRS). [ Time Frame: Weekly and bi-weekly assessments ] [ Designated as safety issue: No ]
  

This is a Phase II, randomized, double-blind, placebo-controlled, parallel-group, multi-center study comparing the efficacy, safety and tolerability of CX157 60mg TID and placebo. This study will be conducted at approximately 12 investigative sites in the US.

Subjects with suspected MDD and experiencing an MDE who the investigator wishes to consider for enrollment in the study and who provide written informed consent will initially be evaluated by the IDS-SR30 administered via IVRS. Subjects who meet the minimum score of 40 on the IDS-SR30 will proceed with the remaining study related assessments at the Screening visit. Those subjects who meet all inclusion criteria and none of the exclusion criteria will enter a one to two week Screening period to confirm eligibility and to capture Screening data prior to Randomization. At the Randomization visit, all eligibility requirements will be reconfirmed. The subjects who meet all criteria will be randomized to study medication and enter into a six-week treatment period and a subsequent one week Follow-Up period. The total duration of participation for subjects who complete all phases of the study will be approximately 8-9 weeks. During the treatment period, clinic visits will occur at Week1, Week 2, Week 4, and Week 6. A subsequent clinic visit will occur at the end of the one week Follow-Up period. The clinical site will contact the subjects via telephone at Weeks 3 and 5 to inquire about their wellbeing, query about adverse events and administer the suicidality scale.

Eligible subjects will be randomized (1:1) to receive:

• CX157 60mg TID, or
• Placebo Subjects who discontinue from the study for any reason will not be replaced.

Inclusion Criteria:

• Male or female = 18 years of age and <60 years
• Able to read, understand, converse in English
• Willing to comply with diet restrictions, concomitant medication restrictions, & all study requirements
• Good general health as ascertained by:Medical history, Physical exam, Supine & standing vital signs, Clinical lab evaluations, 12-lead ECG
• Diagnosis of MDD;
• A total score =>40 on the IDS-SR30 assessed via IVRS at Screening and Randomization

Exclusion Criteria:

• Subject's current MDD episode is >2 years
• History of Substance Use Disorder at Screening or 12 months prior (except for nicotine)

• Current diagnosis of Obsessive-Compulsive Disorder;

  • Panic Disorder or Post-Traumatic Stress Disorder;
  • Anorexia nervosa, Bulimia nervosa, or eating disorder not otherwise specified;
  • Any Axis I Disorder clinically predominant to their MDD (within 6 mo);
  • Presence of psychotic features with current depressive episode;
  • Antisocial or Borderline Personality Disorder
• At risk for suicide
• Lack of response to >2 trials of adequate dose & duration of antidepressants of different mechanistic classes
• Electroconvulsive therapy within 1 year of Screening
• Subject has taken any psychoactive drug within 2 weeks of Randomization
• HX of cardiac abnormalities including abnormal vital sign measurements
• Clinically significant abnormal ECG at Screening

• History within past 2 years of: Significant head trauma;

  • Surgical procedure involving brain or meninges; Encephalitis or meningitis;
  • Degenerative CNS disorder (Alzheimer's or Parkinson's);
  • Epilepsy;
  • Mental retardation
• Clinically significant LFT and other lab abnormalities
• A history of hypothyroidism and treatment with a stable dosage of thyroid replacement medication for <6 months prior to Screening
• A history of hyperthyroidism treated (medically or surgically) <6 months prior to Screening
• Participation in a clinical investigation of a psychotropic drug within 90 days prior to Screening OR used any other investigational drug within 60 days prior to Screening

• Presence of any medical history which includes:

  • Hypersensitivity to CX157 or excipients, other MAO inhibitors, or other phenylethylamines;
  • Diabetes mellitus Type I, uncontrolled Type II, or controlled Type II managed with insulin; Malignancy/chemotherapy within 2 years prior to Screening;
  • Malignancy >2 yrs may not preclude participation if the malignancy was local and without metastasis or recurrence and, if treated with chemotherapy, had no nervous system complications (e.g basal cell carcinoma);
  • Pheochromocytoma
• Positive urine test for drugs of abuse (blood for alcohol)
• Female subject who is pregnant or lactating
• Poor likelihood of subject's cooperation or compliance