Patient description: The patient is a 47-year-old Asian woman complaining of persistent feelings of sadness. She lost interest in activities she used to enjoy. She states that her mood is mostly depressed for the past 3 weeks. She also lost her appetite , which led to about 5kg weight loss. She complains of loss of energy and feelings of worthlessness nearly every day. She is not using any drugs and she does not smoke. She doesn't drink alcohol. She used to exercise every day for at least 30 min. But she doesn't have enough energy to do so for the past 3 weeks. She also has some digestive issues recently. She is married and has 4 children. She is menopausal. Her husband was recently diagnosed with colon cancer and he is starting his chemotherapy. There is nothing remarkable in her past medical history and her drug history is only positive for Vit D3 1000 units daily. Her family history is negative for any psychologic problems. Her HAM-D score is 20.

Clinical trial eligibility criteria: eligible ages (years): 18.0-64.0,  Depressive Disorder, Major Participant with diagnosis of MDD as diagnosed by Structured Clinical Interview for Diagnostic and Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) Clinical Trial Version [SCID-5-CT], with symptoms that have been present for at least a 4-week period. 2. Participant has a Hamilton Rating Scale for Depression (HAM-D) total score ≥24 at screening and Day 1 (prior to dosing). 3. Participants taking antidepressants must have been taking these medications at the same dose for at least 60 days prior to Day 1. Participants who have stopped taking antidepressants within 60 days must have stopped for longer than 5 half-lives of the antidepressant prior to Day 1. Participants receiving psychotherapy must have been receiving therapy on a regular schedule for at least 60 days prior to Day 1. 4. Participant is willing to delay start of other antidepressant or antianxiety medications and any new pharmacotherapy regimens, including as-needed benzodiazepine anxiolytics and sleep aids, until after completion of the Day 42 visit  Participant is currently at significant risk of suicide, as judged by the Investigator, or has attempted suicide associated with the current episode of MDD. 2. Participant has onset of the current depressive episode during pregnancy or 4 weeks postpartum, or the participant has presented for screening during the 6-month postpartum period. 3. Participant has a body mass index (BMI) ≤18 or ≥45 kg/m^2 at Screening, which is subject to a broader evaluation of medical comorbidities. 4. Participant has treatment-resistant depression, defined as persistent depressive symptoms despite treatment with adequate doses of antidepressants within the current major depressive episode (excluding antipsychotics) from two different classes for at least 4 weeks of treatment. 5. Participant has a medical history of seizures, bipolar disorder, schizophrenia, and/or schizoaffective disorder. 6. Participant has a history of mild, moderate, or severe substance use disorder (including benzodiazepines) diagnosed using DSM-5 in the 12 months prior to screening. 7. Participant is taking psychostimulants (eg, methylphenidate, amphetamine) or opioids, regularly or as-needed, at Day -28