This is a multicenter, open-label, fixed dose, 26 week study of patients with MDD. Eligible patients from the lead-in studies will enter the Open-label Safety Study at the Screening/Baseline Visit (Visit 1/Day 1), at which point patient eligibility will be assessed and informed consent obtained.

At the Screening/Baseline Visit (Visit 1/Day 1), which is the same visit as Visit 8/Day 43 of the lead-in study, eligible patients will receive open-label lumateperone 42 mg once daily for approximately 26 weeks. Patients will continue their background ADT from the lead-in study. Patients will be seen for weekly visits through Visit 5/Week 4. Thereafter, visits will occur every two weeks. A Safety Follow-up visit will occur on Visit 17/Day 197, approximately 2 weeks after the last dose of open-label lumateperone 42 mg.

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.