PM8002 or Placebo Plus Nab-Paclitaxel as First-line Treatment in Inoperable Locally Advanced/Metastatic TNBC

Inclusion Criteria:

• Ability to understand and willing to provide written informed consent and to complywith scheduled visits and study procedures;

• Female, aged 18 to 70 years (inclusive);

• Histologically confirmed unresectable locally advanced or metastatic breast cancerwith negative status for ER, PR, and HER-2. Testing results for all three markersconducted within 24 months prior to the initiation of the study by a local facilityaccredited by clinical research center are acceptable. If deemed necessary by theinvestigator during screening, subjects may provide additional biopsy to confirm thelatest pathological;

• Subjects who have not received prior systemic treatment（except endocrine therapy）for advanced breast cancer are eligible for the study. Subjects who have receivedTaxane-based chemotherapy during the neoadjuvant and/or adjuvant treatment phase areeligible, as long as the occurrence of relapse or metastasis is at least 12 monthsafter the end of treatment;

• Performance status as assessed by the Eastern Cooperative Oncology Group (ECOG) is 0-1;

• Life expectancy of 12 weeks or more;

• According to RECIST 1.1, the subject has at least 1 measurable lesion as thetargeted lesion (the only bone metastasis or the only central nervous systemmetastasis should not be considered as a measurable lesion. A measurable lesionlocated at the previously irradiated radiation field or other local treatment areashould not be selected as targeted lesion, unless the lesion shows unequivocalradiographic progression).

Exclusion Criteria:

• Previous treatment with immune checkpoint agonists (such as CD137 agonists) orimmune checkpoint inhibitors (such as CTLA-4, PD-1, PD-L1, LAG3 monoclonal antibody,etc.) or anti-vascular endothelial growth factor (VEGF) target drugs;

• Has uncontrolled or symptomatic brain or spine cord metastases;

• Those who have had other active malignant tumors within 5 years prior to the studytreatment, except for those that can be treated locally and have been cured ;

• Poorly controlled hypertension (systolic blood pressure ≥ 140 mmHg and/or diastolicblood pressure ≥ 90 mmHg);

• With a history of hypertensive crisis or hypertensive encephalopathy;

• With a history of abdominal fistula, tracheoesophageal fistula, gastrointestinalperforation, or intra-abdominal abscess within the last 6 months prior to the startof the study treatment;

• Adverse events resulting from prior anti-tumor therapies should be assessed andgraded according to the CTCAE 5.0 criteria, subjects whose AEs have not returned toGrade 1 or below;

• Has uncontrollable pleural, pericardial, or abdominal effusions;

• Has received allogeneic hematopoietic stem cell transplantation or organtransplantation.