A Study of CX157 (TriRima) for the Treatment of Depression

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 Major Depressive Disorder (MDD) and experiencing a Major Depressive Episode (MDE) who the investigator wishes to consider for enrollment in the study and who provide written informed consent will initially be evaluated by the Inventory of Depressive Symptomatology 30 item -Self Report (IDS-SR30) administered via Interactive Voice Response System (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 Week 1, 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 three times a day (TID) for a total daily dose of 180 mg, or * Placebo administered three times a day. Subjects who discontinue from the study for any reason will not be replaced.