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 curativeintent.

3. No prior systemic anti-cancer therapy for unresectable recurrent or metastaticdisease.

4. Participants whose tumours are PD-L1-negative, or participants whose tumors arePD-L1 positive and have relapsed after prior anti-PD-1/PD-L1 inhibitor forearly-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 noworsening 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 bythe 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 requiredsteroids 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 immunodeficiencysyndrome (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.