A Study of SKB264 Versus Investigator's Choice Chemotherapy in Patients With Unresectable Recurrent or Metastatic Triple-Negative Breast Cancer

Key Inclusion Criteria: 1. Histologically and/or cytologically confirmed TNBC. 2. De novo metastatic or relapsed ≥ 6 months post completion of treatment with curative intent. 3. No prior systemic anti-cancer therapy for unresectable recurrent or metastatic disease. 4. Participants whose tumours are PD-L1-negative, or participants whose tumors are PD-L1 positive and have relapsed after prior anti-PD-1/PD-L1 inhibitor for early-stage disease. 5. At least one measurable lesion per RECIST v1.1. 6. Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1 with no worsening within 2 weeks prior to randomization. 7. A life expectancy of at least 3 months. 8. Eligible for the chemotherapy options listed as investigator's choice chemotherapy (paclitaxel, nab-paclitaxel, capecitabine, eribulin, or carboplatin) as assessed by the investigator. 9. Adequate organ and bone marrow function. Key Exclusion Criteria: 1. Active second malignancy. 2. Uncontrolled or clinical significant cardiovascular disease. 3. History of noninfectious pneumonitis/interstitial lung disease (ILD) that required steroids or has current pneumonitis/ILD. 4. Active infection requiring systemic therapy within 2 weeks of randomization. 5. Active hepatitis B or hepatitis C virus infection. 6. Human immunodeficiency virus (HIV) positive or history of acquired immunodeficiency syndrome (AIDS); known active syphilis infection. 7. Known hypersensitivity to SKB264 or its excipients. 8. Previously received TROP2-targeted therapy or topoisomerase 1 inhibitors. 9. Prior treatment with the same investigator's choice chemotherapy (except taxane). 10. Pregnant or lactating women.