Efficacy, Safety and Tolerability of Cariprazine as an Adjunctive Treatment to Antidepressant Therapy (ADT) in Patients With Major Depressive Disorder (MDD) Who Have Had an Inadequate Response to Antidepressants Alone

* Written informed consent has been obtained. * Written documentation has been obtained in accordance with the relevant country and local privacy requirements, where applicable (eg, Written Authorization for Use and Release of Health and Research Study Information \[US sites\] and written Data Protection consent \[EU sites\]). * Patient must be an outpatient at the time of Visit 1 (Screening). * Patient meets the DSM-5 criteria for MDD based on SCID-5, with a current major depressive episode of at least 8 weeks and not exceeding 24 months in duration at Visit 1/Screening. A diagnosis of MDD with psychotic features will be acceptable. * Diagnosis of MDD confirmed through a formal adjudication process. * Patient demonstrates ability to follow study instructions and likely to complete all required visits. * Patient must have an inadequate response, as measured by the modified ATRQ, to 1 to 3 antidepressants administered during the current episode at an adequate dose (as per package insert) and for at least 6 weeks duration, with at least one dose escalation during the current depressive episode. * Only one antidepressant (of sufficient dose per package insert and taken for at least 6 weeks) will be allowed at randomization and patients must agree to continue taking the same ADT dosing regimen through completion of Visit 6/ET. Patients who are taking more than one antidepressant at Screening, regardless of the indication, will need to discontinue all other antidepressants prior to Visit 2 (Baseline). * Male and female patients must agree to use a medically acceptable and highly effective method of birth control during the course of the entire study. * Women of childbearing potential (only) must have a negative serum β-human chorionic gonadotropin pregnancy test prior to Visit 2.

* Diagnosis of any current psychiatric diagnosis other than MDD (including those with current intellectual development disability) with the exception of specific phobias. * Patient has a history of intolerance or hypersensitivity to cariprazine or other drugs of the same class or to rescue medications.