A Study of BL-B01D1 Plus an Anti-PD-1 Antibody Versus Nab-paclitaxel Plus an Anti-PD-1 Antibody in Patients With Previously Untreated, Locally Advanced, Inoperable or Metastatic Triple-Negative Breast Cancer Whose Tumors Express PD-L1 (PANKU-Breast04)

Prior treatment

• Received surgery, radical radiotherapy, or immunotherapy within 4 weeks before the first dose;
• Prior exposure to ADC drugs with topoisomerase I inhibitor payload;
• Prior treatment with other T-cell receptor-targeting agents (excluding PD-1/PD-L1);
• Use of immunomodulators within 14 days before the first study drug dose;
• Receiving chronic systemic corticosteroids at \>10 mg/day prednisone before the first dose;
• Any thrombotic event within 6 months before randomization;
• Concurrent lung disease causing clinically significant respiratory impairment;
• Severe infection within 4 weeks before randomization;
• Severe non-healing wound, ulcer, or fracture within 4 weeks before consent;
• Clinically significant bleeding or bleeding tendency within 4 weeks before consent;
• Received or planning to receive live vaccine within 28 days before randomization;

Other illness

• History of severe cardiac or cerebrovascular disease;
• Active autoimmune or inflammatory disease;
• Active malignancy diagnosed within 3 years before randomization;
• Hypertension uncontrolled by two antihypertensives;
• Poorly controlled diabetes/hyperglycemia;
• History of steroid-treated ILD/interstitial pneumonitis;
• Inflammatory bowel disease, extensive bowel resection, immune enteritis, bowel obstruction, or chronic diarrhea;
• Allergy or contraindication to the study drug;
• History of autologous/allogeneic stem cell transplantation;
• HIV antibody positive, active HBV, or active HCV;
• History of severe neurological or psychiatric illness;
• Other conditions rendering the patient unsuitable per investigator's judgment.

Lab values

• Prolonged QTc, complete left bundle branch block, or similar;

Other

• Active CNS metastases;
• Massive or symptomatic serosal effusion;

• Voluntarily sign the informed consent form and agree to comply with the protocol requirements;
• Female patients aged 18 to 75 years;
• Expected survival time ≥ 3 months;
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1;
• Pathologically confirmed recurrent or metastatic triple-negative breast cancer;
• Confirmed PD-L1 expression positivity by central laboratory testing;
• No prior systemic anti-tumor therapy in the advanced/recurrent or metastatic setting;
• Agree to provide archived tumor tissue specimens (surgical specimens) or fresh tissue samples from primary or metastatic lesions obtained within 3 years;
• Must have at least one measurable lesion as defined by RECIST v1.1;
• Toxicities from prior anti-tumor therapy must have recovered to ≤ Grade 1 as defined by NCI-CTCAE v6.0;
• No severe cardiac dysfunction, with left ventricular ejection fraction (LVEF) ≥ 50%;
• Organ function levels must meet the protocol-specified requirements;
• Urine protein ≤ 1+ or \< 1000 mg/24 h;
• For premenopausal women of childbearing potential, a pregnancy test (serum) must be performed within 7 days before starting treatment, and pregnancy must be ruled out; patients must not be lactating. All enrolled patients (regardless of sex) must use adequate barrier contraception throughout the entire treatment period and for 7 months after the end of treatment.