This phase II study is a clinical study to explore the efficacy and safety of BL-B01D1 combined with PD-1 monoclonal antibody in patients with unresectable locally advanced or recurrent metastatic triple-negative breast cancer.

Inclusion Criteria:

1. Voluntarily sign the informed consent and follow the requirements of the protocol;
2. Age: ≥18 years old and ≤75 years old;
3. Expected survival time ≥3 months;
4. ECOG 0 or 1;
5. Subjects with histologically and/or cytologically confirmed, inoperable locally advanced or recurrent or metastatic triple-negative breast cancer;
6. Patients should not have received previous systemic therapy for unresectable, locally advanced, recurrent, or metastatic triple-negative breast cancer;
7. A archived tumor tissue specimen or fresh tissue specimen of the primary or metastatic lesion within 2 years must be provided;
8. Must have at least one place in accordance with RECIST v1.1 define measurable lesions;
9. No blood transfusion, no use of cell growth factors and/or platelet raising drugs within 14 days before screening, and the organ function level must meet the requirements;
10. Toxicity of previous antineoplastic therapy has returned to ≤ grade 1 defined by NCI-CTCAE v5.0;
11. For premenopausal women with childbearing potential, a pregnancy test must be performed within 7 days before the initiation of treatment, the serum or urine pregnancy test must be negative, and the patient must not be lactating; All enrolled patients should take adequate barrier contraception during the entire treatment cycle and for 6 months after the end of treatment.

Exclusion Criteria:

1. ADC drugs that have received topoisomerase I inhibitors as small molecule toxins;
2. Palliative radiotherapy within 2 weeks before the first dose;
3. Patients with checkpoint inhibitors prior to neoadjuvant/adjuvant chemotherapy;
4. Use of an immunomodulatory drug within 14 days before the first dose of study drug;
5. The history of severe cardiovascular and cerebrovascular diseases in the past six months was screened;
6. QT prolongation, complete left bundle branch block, III degree atrioventricular block, frequent and uncontrollable arrhythmia;
7. Active autoimmune and inflammatory diseases;
8. Receiving long-term systemic corticosteroid therapy, etc., before the first dose;
9. Other malignant tumors that progressed or required treatment within 5 years before the first dose;
10. Presence of: a) poorly controlled diabetes mellitus before starting study treatment; b) severe complications associated with diabetes mellitus; c) a glycated hemoglobin level of 8% or more; d) hypertension poorly controlled by two antihypertensive drugs; e) history of hypertensive crisis or hypertensive encephalopathy;
11. Present grade ≥2 radiation pneumonitis according to the RTOG/EORTC definition; Patients with current ILD;
12. Complicated with pulmonary diseases leading to clinically severe respiratory impairment;
13. 6 months prior to screening needs treatment intervention unstable thrombotic events;
14. Patients with active central nervous system metastases;
15. Patients with massive or symptomatic effusions or poorly controlled effusions;
16. Allergic history to recombinant humanized antibody or human-mouse chimeric antibody or allergic to any excipients of the test drug;
17. Prior organ transplantation or allogeneic hematopoietic stem cell transplantation;
18. HIV antibody positive, active tuberculosis, active hepatitis B virus infection, or active hepatitis C virus infection;
19. Serious infection within 4 weeks before the first dose of study drug; Signs of pulmonary infection or active pulmonary inflammation within 4 weeks;
20. Participated in another clinical trial within 4 weeks before the first dose;
21. Patients with superior vena cava syndrome should not be rehydrated;
22. Have a history of psychotropic substance abuse with an inability to quit or a history of severe neurological or psychiatric illness;
23. Imaging examination showed that the tumor had invaded or wrapped the large thoracic vessels;
24. Serious unhealed wound, ulcer, or fracture within 4 weeks before signing the informed consent;
25. Clinically significant bleeding or obvious bleeding tendency within 4 weeks before signing the informed consent;
26. Subjects who are scheduled to receive live vaccine or receive live vaccine within 28 days before the first dose;
27. Other circumstances considered by the investigator to be inappropriate for participation in the trial.