A Study to Assess Adverse Events and Change in Disease Activity of Oral Icalcaprant in Adult Participants With Bipolar I or II Disorder

Bipolar disorder is a severe chronic mood disorder that affects up to 4% of the adult population and 1.8% of the pediatric population in the United States. This study will assess how safe and effective Icalcaprant is in treating adult participants with bipolar I or II disorder.

Icalcaprant is an investigational drug being developed for the treatment of depressive episodes in adult participants with bipolar I or II disorder. Participants are placed in 1 of 3 groups, called treatment arms. There is a 1 in 3 chance that a participant will be assigned to a placebo. Around 237 adult participants with bipolar I or II disorder will be enrolled in approximately 45 sites worldwide.

Participants will receive oral capsules of Icalcaprant or matching placebo once daily for 6 weeks, with a 4-week safety follow-up period.

There may be a higher treatment burden for participants in this trial compared to their standard of care. Participants will attend regular visits during the study at a hospital or clinic. The effect of the treatment will be checked by medical assessments, blood tests, checking for side effects and completing questionnaires.


Eligibility Criteria:
Inclusion Criteria:

* Participants with a diagnosis of bipolar I or II according to the (Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition) DSM-5-TR) without psychotic features, confirmed by the Mini International Neuropsychiatric Interview (MINI) 7.0.2, currently experiencing an (major depressive episode) MDE beginning at least 4 weeks prior to consent and not exceeding 6 months prior to screening
* Body Mass Index (BMI) is ≥ 18.0 to ≤ 35.0 kg/m\^2
* A condition of general good health, based upon the results of a medical history, physical examination, vital signs, laboratory profile and a 12-lead ECG.
* CGIS-BP score of ≥ 4 for depression and overall bipolar illness at screening (Visit 1) and baseline (Visit 2)
* YMRS total score ≤ 12 at screening (Visit 1) and baseline (Visit 2)
* Participants must have had ≥ 28 days of treatment prior to screening with valproate or lithium at therapeutic blood levels (0.4-1.5 mEq/L, 50-125 μg/mL).

Exclusion Criteria:

* History of any treatment with antidepressants for any reason within 7 days, fluoxetine within 28 days, a monoamine oxidase inhibitor within 21 days of randomization, clozapine within 120 days of randomization, or benzodiazepines or sedative hypnotics within 7 days of randomization.
* History of an allergic reaction or significant sensitivity to constituents of the study drug (and its excipients) and/or other products in the same class.
* History of or active medical conditions(s) that might interfere with the conduct of the study, confound the interpretation of the study results, or endanger the subject's well-being. This includes any unstable condition, history or evidence of malignancy (other than treated basal or squamous cell carcinoma), or any significant hematologic, endocrine, cardiovascular, respiratory, renal, hepatic, gastrointestinal, or neurological disorder (if there is a history of such disease but the condition has been stable for more than 1 year, does not require treatment with prohibited medications, and is judged by the investigator not to interfere with the participant's participation in the study, the participant may be included in the study).