This is an open-label, multi-center, phase II clinical study to preliminarily evaluate the efficacy and safety of JS207 combined with 9MW2821 or albumin paclitaxel as first-line therapy in patients with recurrent or metastatic TNBC.

The study consists of Cohort A and Cohort B. Both cohorts include patients with recurrent or metastatic TNBC who have not received systemic anti-tumor therapy previously. Cohort A will receive JS207 combined with 9MW2821, and Cohort B will receive JS207 combined with albumin paclitaxel. Each cohort consists of two stages: safety run-in period and cohort expansion period.

Inclusion Criteria:

1. Male or female age 18 - 75 years old；
2. Voluntary participation in clinical study；
3. Histologically confirmed unresectable, locally advanced or metastatic triple-negative breast cancer(absence of HER2, ER, and PR expression);
4. No prior systemic antitumor therapy for locally advanced or Metastatic TNBC；
5. Prior use of systemic anti-tumor therapy in the neoadjuvant and/or adjuvant phase is allowed, but must meet the following conditions: (1) the time interval between the end of neoadjuvant/adjuvant therapy and the occurrence of recurrence/metastasis is ≥6 months; (2) Arm2: if taxane is used in the neoadjuvant/adjuvant phase, the DFI must be ≥12 months;
6. Adequate organ function;
7. ECOG performance status of 0 or 1;
8. Life expectancy 12 weeks;
9. Measurable disease, as defined by RECIST v1.1;

Exclusion Criteria:

1. Untreated or active central nervous system (CNS) metastases；
2. Uncontrolled pleural effusion, pericardial effusion or ascites；
3. Tumor encasement of important vessels or significant necrosis and cavitation that may cause a risk of hemorrhage；
4. History of significant bleeding tendency or severe coagulation disorder；
5. Uncontrolled hypertension；
6. Active autoimmune diseases requiring systemic treatmen within 2 years prior to the first dose；
7. History of interstitial lung disease or previous Noninfectious pneumonitis treated with corticosteroids, or evidence of active Pneumonia in radiology on screening period；
8. Eye disorders or symptoms: severe xerophthalmia, keratoconjunctivitis sicca, severe exposure keratitis, or other conditions；
9. Severe cardiovascular disease；
10. Serious infection (CTCAE 5.0 Grade>2) within 28 days prior to the first dose of study drug；
11. Previous treatment with anti-PD-1, anti-PD-L1 or anti-PD-L2 drugs or drugs targeting other stimulatory or co-inhibitory T cell receptors (e.g., CTLA-4, OX-40, CD137) in (new) adjuvant therapy is allowed, if DFI is ≥6 months previously treated with Antibody-Drug Conjugates conjugated with MMAE and/or targeting Nectin-4, such as Enfortumab Vedotin is not allowed；
12. History of another malignancy within 5 years before the first dose of study drug；
13. Not suitable to receive study treatment for other conditions as per investigator；

None(open label)