Major depressive disorder (MDD; depression) is a mood disorder that causes a continued feeling of sadness and loss of interest. It is a common and serious illness that can cause both emotional and physical symptoms such as feelings of sadness, irritability, not being able to focus on activities, tiredness, changes in eating habits, and aches and pains. This study will assess the changes in disease activity and adverse events of oral Icalcaprant in adult participants with major depressive disorder who are currently experiencing a major depressive episode (MDE).

Icalcaprant is an investigational drug being developed for the treatment of depressive episodes in adult participants with major depressive 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 placebo treatment. Around 195 adult participant with major depressive disorder will be enrolled in approximately 35 sites in North America.

Participants will receive oral capsules of Icalcaprant or matching placebo once daily for 6 weeks, with a 30-day safety follow-up.

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.

Inclusion Criteria:

• Participants with a diagnosis of major depressive disorder (MDD) according to the Diagnostic and Statistical Manual of Mental Disorders, fifth edition, text revision (DSM-5-TR) without psychotic features, confirmed by the Mini International Neuropsychiatric Interview (MINI) 7.0.
• Body Mass Index (BMI) is ≥ 18.0 to ≤ 35.0 kg/m^2
• Currently experiencing an major depressive episode (MDE) beginning at least 4 weeks prior to consent and not exceeding 6 months prior to Screening
• Normal physical examination findings, clinical laboratory test results, vital signs, and 12-lead ECG results at Visit 1 or abnormal results that are judged not clinically significant by the investigator and documented as such in the eCRF.

Exclusion Criteria:

• Has failed (no more than 25% response on Antidepressant Treatment History Questionnaire (ATRQ)) 3 or more antidepressant treatments during the current depressive episode despite an adequate dose (per ATRQ) and duration (at least 6 weeks).
• 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.

AbbVie is committed to responsible clinical trial data sharing. This includes access to anonymized, individual and trial-level data (analysis data sets), as well as other information.

For details on when studies are available for sharing, visit https://vivli.org/ourmember/abbvie/

To learn more about the process, or to submit a request, visit the following link https://www.abbvieclinicaltrials.com/hcp/data-sharing/