Inclusion criteria:
1. Aged 18-65 years (inclusive);
2. With first-episode or relapsed depression that meets the DSM-5 diagnostic criteria;
3. With a Hamilton's Depression Scale (HAMD-17) score of ≥18 at enrollment;
4. Receiving no antidepressants within 2 weeks (fluoxetine within 6 weeks) prior to enrollment;
5. Willing to sign the informed consent form (ICF).
Exclusion criteria:
1. Meeting the DSM-5 diagnostic criteria for mental disorders other than depression (e.g., patients with schizophrenia spectrum and other psychiatric disorders, bipolar and related disorders, compulsive and related disorders, etc.);
2. With refractory depression (no response to adequate treatment with 2 or more antidepressants) as determined by the investigator or previously diagnosed;
3. At a significant risk of suicide (HAMD-17 Item 3 (suicide) score ≥3) as judged by the investigator, or with a history of suicide attempts in the last year;
4. Receiving non-drug therapies, such as electric convulsive therapy (ECT), repetitive transcranial magnetic stimulation (rTMS), and systematic psychotherapy 10 or more times in the last 6 months;
5. With other serious chronic diseases such as severe thyroid disease, Parkinson's disease, tumor, epilepsy, and severe rheumatism;
6. With clinically significant abnormalities in 12-lead ECG that may affect the safety of the subject, including but not limited to acute myocardial ischemia, myocardial infarction, severe arrhythmia, or significantly prolonged QTc (QTc \>450 ms in men and \>470 ms in women);
7. With severe hepatic and renal insufficiency, i.e., aspartate transaminase (AST) ≥1.5 × upper limit of normal (ULN) or alanine aminotransferase (ALT) ≥1.5 × ULN, and serum creatinine (Scr) ≥1.5× ULN;
8. Allergic to the investigational drug or its ingredients;
9. In lactation, of childbearing potential, or planning to be pregnant;
10. With alcohol and drug dependence;
11. Participating in another clinical study within 1 month prior to enrollment or for the time being.
12. Not suitable for participation in this study due to potential risks or other factors as considered by the investigator.
