An Open-label Study of Lumateperone as Adjunctive Therapy in the Treatment of Patients With Major Depressive Disorder

Inclusion Criteria: 1. In the opinion of the Investigator, patients must have safely completed the lead-in study. 2. Patient is taking their ADT as prescribed from the lead-in study. Exclusion Criteria: 1. In the opinion of the Investigator, the patient is unable to comply with study procedures or judged to be inappropriate for the study. 2. In the opinion of the Investigator, the patient has a significant risk for suicidal behavior during the course of her/his participation in the study or is considered to be an imminent danger to her/himself or others, and/or: 1. At the Screening/Baseline Visit, the patient scores "yes" on Suicidal Ideation Items 4 or 5 of the C SSRS "Since Last Visit" version; 2. At the Screening/Baseline visit, the patient scores ≥ 5 on the MADRS Item 10 (Suicidal Thoughts). 3. Based on the Investigator's clinical judgement, any abnormal clinical laboratory test or ECG results obtained throughout the lead-in study that are considered clinically significant and preclude safe participation in the study.