Study of ABX-002 for the Adjunctive Treatment of Depressive Episodes Associated With Bipolar Disorder in Adults

The goal of this clinical trial is to learn if ABX-002 added to participants' existing treatment(s) can improve clinical symptoms of depression and to learn about potential effects on brain chemistry that may correlate with antidepressive effects. This is a single treatment arm, open-label, Phase 2 study of ABX-002 in up to30 adults with bipolar depression. A subset of these participants will undergo brain imaging. Five healthy volunteer participants will also be enrolled and receive no drug treatment, undergoing 2 imaging sessions to confirm instrument and test - retest method reliability control. For bipolar disorder participants who are experiencing an episode of depression, the study will include 4 study periods: 1. Screening Period of up to 5 weeks 2. 6-week Treatment Period 3. 2-week post dose Safety Follow-up Period. 4. 6-month postdose targeted safety follow-up period For healthy volunteers, the study will include 2 study periods: 1. Screening Period of up to 3 weeks 2. Imaging Period of up to 3 weeks.