A Phase III Study of ESG401 for Unresectable Recurrent or Metastatic Triple-Negative Breast Cancer

Key Inclusion Criteria: 1. Males or females aged ≥ 18 years ; 2. Histologically and/or cytologically confirmed TNBC; 3. De novo metastatic or relapsed ≥ 6 months post completion of treatment with curative intent; 4. No prior systemic anti-cancer therapy for unresectable recurrent or metastatic disease; 5. Participants whose tumours are PD-L1-negative, or Participants whose tumours are PD-L1-positive and have relapsed after prior PD-1/PD-L1 inhibitor therapy for early-stage breast cancer, or comorbidities precluding PD-1/PD-L1 inhibitor therapy; 6. Eligible for the chemotherapy options listed as investigator's choice chemotherapy (paclitaxel, nab-paclitaxel, capecitabine, eribulin, or carboplatin) as assessed by the investigator; 7. At least one measurable lesion per RECIST v1.1; 8. Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1 with no worsening within 2 weeks prior to randomization; 9. A life expectancy of at least 12 weeks; 10. Adequate organ and bone marrow function. Key Exclusion Criteria: 1. Use of any investigational anti-cancer drug within 28 days or 5 half-lives before the first investigational product administration. 2. Toxicities from prior anti-tumor therapy not recovering to ≤ Grade 1. 3. Prior topoisomerase I inhibitor therapy, including antibody-drug conjugate(ADC) therapy, or prior TROP2 targeted therapy. 4. New thromboembolic events, intestinal obstruction, gastrointestinal bleeding or perforation within 6 months. 5. Subjects with symptomatic or untreated CNS metastases, or those requiring ongoing treatment for CNS metastases. 6. Patients with Primary CNS malignancy, or patients with other malignancies within 3 years prior to the first dose. 7. Patients with uncontrollable systemic diseases. 8. Patients with gastrointestinal diseases (such as chronic gastritis, chronic enteritis or gastric ulcers), or with a previous history of severe or chronic diarrhea. 9. Subjects with clinically significant cardiovascular disease. 10. Human Immunodeficiency Virus (HIV) infection. 11. Active hepatitis B or hepatitis C. 12. Known immediate or delayed hypersensitivity reaction to irinotecan or other camptocampin derivatives such as topotecan or to have had grade≥3 gastrointestinal reactions associated with irinotecan, or allergies, or to any investigational drug or excipient ingredient. 13. Pregnant or lactating women.