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

Inclusion Criteria (For Bipolar Disorder Depression Patients): * Current diagnosis of bipolar disorder for at least 2 years * DSM-5-TR criteria for bipolar disorder based on Structured Clinical Interview for the DSM-5 - Clinical Trials Version (SCID-5-CT) at Screening * Has a current depressive episode with or without mixed features, but not psychotic features, with duration ≥ 6 weeks and ≤ 24 months * 17-item Hamilton Rating Scale for Depression total score ≥ 22 at Screening and Baseline * Young Mania Rating Scale total score ≤ 12 at Screening and Baseline * For participants who will undergo brain imaging: Able to undergo imaging sessions using Magnetic Resonance Spectroscopy/Imaging with no history of aborted scanning due to anxiety, claustrophobia, or unable to scan due to an incompatible implant/device * Taking at least one mood stabilizer (e.g., lithium, valproate, lamotrigine) and/or second-generation antipsychotic (SGA, atypical antipsychotic). All medications intended to treat the current episode of depression should be at an adequate and stable dose for ≥ 6 weeks prior to screening. Exclusion Criteria (For Bipolar Disorder Depression Patients): * History of \> 4 manic, hypomanic, or depressive episodes within a one-year period (rapid cycler; DSM-5-TR) in the last 2 years * History of schizophrenia or schizoaffective disorder (DSM-5-TR) or a psychotic disorder unrelated to bipolar disorder * Concurrent or history of active symptoms within the past 2 years of obsessive-compulsive disorder, or posttraumatic stress disorder, according to DSM-5-TR criteria * Diagnosis of a personality disorder (DSM-5-TR) * Evident risk of suicide at Screening or Baseline * Inadequate response to more than 2 second-generation antipsychotic treatments (including their current treatment) in their current episode of depression in bipolar disorder despite an adequate dose and duration (\> 6 weeks at approved or standard of care doses) * Received any course of deep brain stimulation in participant's lifetime or plans to receive deep brain stimulation during the study * Treatment with electroconvulsive therapy (for psychiatric/therapeutic purposes) or repetitive transcranial magnetic stimulation, or treatment with ketamine or esketamine for the current episode and received any of those treatments within 12 months prior to Screening * Started new psychotherapy or had a change in the intensity of psychotherapy within 6 weeks before Screening * Prior use of psychedelics for the treatment of depression * Refusal to abstain from consumption of excessive amounts of alcohol during the study * History of uncontrolled, clinically significant neurological (including prior cerebrovascular accident \[stroke\] or chronic seizures), cardiovascular, gastrointestinal, respiratory, renal, hepatic, immunological, hematological, endocrine (including uncontrolled diabetes), or other medical disorder, including cancer * Current use of high dose (\> 4 mg/day lorazepam equivalents) benzodiazepine anxiolytic and/or hypnotic medication * Cannabinoids (marijuana, cannabis, tetrahydrocannabinol \[THC\], cannabidiol \[CBD\]) in any form or use frequency. * History or presence of cataract on ophthalmic examination (including slit-lamp), glaucoma, inflammatory eye disease prior ophthalmic surgical procedures or laser surgery in either eye. Inclusion Criteria (For Healthy Volunteers): * In good health, based on medical history, physical examination (including neurological examination), vital sign measurements, and laboratory safety tests obtained at the Screening Visit * Able to undergo imaging sessions using Magnetic Resonance Spectroscopy/Imaging, with no history of aborted scanning due to anxiety, claustrophobia, or an incompatible implant/device Exclusion Criteria (Healthy Volunteers): * Mentally or legally incapacitated, has significant emotional problems at the time of the Screening Visit, or is expected to have potential for mental incapacitation during the conduct of the study * History of any illness (including psychiatric illness) * Participation in an investigational drug or device study where last dosing of previous drug is within 30 days * Prior use of psychedelics within the past year * Refusal to abstain from consumption of excessive amounts of alcohol during the study * Cannabinoids (marijuana, cannabis, tetrahydrocannabinol \[THC\], cannabidiol \[CBD\]) in any form or use frequency are not allowed.