A Clinical Trial to Determine the Long-term Safety and Tolerability of an Investigational Drug in People With Major Depressive Episode Associated With Bipolar I Disorder (Bipolar I Depression).

Exclusion Criteria

• •Subject is at high risk of non-compliance in the opinion of the Investigator.
• •Subject plans to initiate treatment with a prohibited psychotropic medication during the study.
• •Subject plans to initiate treatment with transcranial magnetic stimulation (TMS), electroconvulsive therapy (ECT), vagus nerve stimulation (VNS), or deep brain stimulation (DBS) during the study.
• •Subject experienced a moderate or severe hyperprolactinemia-related AESI in the lead-in study of SEP-4199 CR.
• •Subject will require treatment with a drug that is associated with increases in QTc interval.
• •Subject had any of the following at Visit 6/EOT (Day 42) of the lead-in study of SEP-4199 CR based on machine reading:
• •increase in QTcF interval of ≥ 30 msec AND a QTcF interval ≥ 480 msec, from baseline of the lead-in study of SEP-4199 CR AND a QTCF interval ≥ 480msec
• •increase in QTcF interval ≥ 60 msec, from baseline of the lead-in study of SEP-4199 CR
• •QTcF interval ≥ 500 msec
• •treatment-emergent clinically significant ECG abnormality.
• •Subject is considered by the Investigator to be at imminent risk of suicide or injury to self or others, has a MADRS item 10 (suicidal ideation) score ≥ 4, or answers "yes" to "suicidal ideation" item 4 (active suicidal ideation with some intent to act, without specific plan) or item 5 (active suicidal ideation with specific plan and intent) on the C-SSRS assessment at Visit 6/EOT (Day 42) of the lead-in study of SEP-4199 CR.
• •Female subject of childbearing potential, has a positive urine pregnancy test at Visit 6/EOT (Day 42) of the lead-in study of SEP-4199 CR or plans to become pregnant during the current study.
• •Subject tests positive for any drug of abuse or cannabis at Visit 6/EOT (Day 42) of the lead-in study of SEP-4199 CR