Study to Assess the Efficacy and Safety of NBI-1065845 in Adults With Major Depressive Disorder (MDD)

Key Inclusion Criteria:

Participants must meet all of these criteria for inclusion in the study:

• The participant has completed written informed consent.
• At the time of signing the informed consent, participant must be 18 to 65 years of age, inclusive.
• The participant has a primary diagnosis of recurrent Major Depressive Disorder (MDD) or persistent depressive disorder.
• Participant must have had inadequate response to antidepressant treatment.
• Participant must have a Total Hamilton Depression Rating Scale-17 Item (HAMD-17) score ≥ 22 at screening.
• Participants currently receiving pharmacological treatment for depression must have been taking current antidepressant medication(s) for ≥8 weeks prior to screening. Subjects not currently receiving pharmacologic treatment for depression must have received the most recent antidepressant medication(s) for ≥8 weeks in the current episode of depression.
• Participants must be willing and able to comply with all study procedures.

Key Exclusion Criteria:

Participants will be excluded from the study if they meet any of the following criteria:

• Participant is pregnant or breastfeeding or plans to become pregnant during the study.
• Participant has an unstable medical condition or unstable chronic disease.
• Participant has a history of neurological abnormalities.
• Participant has a current or prior psychiatric disorder that was the primary focus of treatment other than MDD.
• The participant's depressive symptoms have previously demonstrated nonresponse to an adequate course of treatment with electroconvulsive therapy (ECT).
• The participant has an alcohol or substance use disorder.
• In the Investigator's opinion, the participant is not capable of adhering to the protocol requirements.