A Clinical Study of an Investigational Drug for the Treatment of Major Depressive Episode Associated With Bipolar I Disorder.

Inclusion Criteria:

Inclusion Criteria (not all inclusive):

• Subject provides written informed consent and is willing and able to comply with theprotocol in the opinion of the Investigator.

• Subject is 18 to 65 years of age, inclusive, at the time of informed consent.

• Subject meets DSM-5 criteria, based on the SCID-5-CT, for bipolar I disorder,current episode depressed with or without rapid cycling disease course (≥ 4 episodesof mood disturbance but < 8 episodes in the previous 12 months) with or withoutpsychotic features.

• Subject's current major depressive episode is ≥ 4 weeks and less than 12 months induration at Screening.

• Subject has a MADRS total score ≥ 22 at both Screening and Baseline.

• Subject has a CGI-BP-S depression score ≥ 4 at both Screening and Baseline.

• Subject has a YMRS total score ≤ 12 at both Screening and Baseline.

• Subject is in good physical health, based on medical history, physical examination,neurological examination, vital signs, ECGs, and results of clinical laboratorytests (hematology, chemistry, and urinalysis).

Exclusion Criteria:

Exclusion Criteria (not all inclusive):

• Subject currently has any DSM-5 defined psychiatric diagnosis other than bipolar Idisorder that was the primary focus of treatment, or is currently being treated withconcomitant medication

• Subject has a lifetime history of, or symptoms consistent with, schizophrenia,schizoaffective disorder, or a major psychiatric diagnosis other than bipolar Idisorder that is judged to pose risk to the study scientific objectives

• Subject has a history of non-response to an adequate (6-week) trial of 3 or moreantidepressants (with or without mood stabilizers) during the current majordepressive episode.

• Subject has any clinically significant unstable medical condition or any clinicallysignificant chronic disease that would pose a risk to the subject or that mightconfound the results of the study.