∙ ·You must meet all of the following conditions to be eligible for the group：

• Understand and voluntarily sign the informed consent form;

• Age at screening ranged from 18 to 75 years (including the cutoff value), regardless of gender;

• Locally advanced or metastatic breast cancer that is unresectable as confirmed by histology or cytology, including triple-negative breast cancer, Her-2-positive, and HR-positive breast cancer;

• Histological or cytological tumor specimens were confirmed by immunohistochemistry to have moderate to high expression of nectin-4 (expression intensity ≥2+ and tumor cell positive rate ≥50%);

• Patients who have received standard systemic treatment for breast cancer recommended by the Breast Cancer Diagnosis and Treatment Guidelines (2022 Edition) and have had imaging or other objective evidence of disease progression after receiving standard treatment; or patients with refractory breast cancer who cannot tolerate standard treatment or have contraindications to standard treatment, and who have at least one measurable lesion (according to RECIST version 1.1, the long diameter of the measurable lesion on spiral CT scan is ≥10mm or the short diameter of the enlarged lymph node is ≥15mm, see Appendix 1 for RECIST version 1.1); Note: Treatment failure is defined as disease progression during treatment or recurrence after treatment.

• Definition of intolerance : the occurrence of grade ≥ IV hematological toxicity, grade ≥ III non-hematological toxicity, or grade ≥ III damage to major organs such as heart, liver, and kidney during treatment (refer to NCI-CTCAE v5.0 standards), or a comprehensive assessment by the investigator.

• The expected survival time at enrollment was greater than 12 weeks;

• During screening, laboratory tests must meet the following requirements:

‣ White blood cell count ≥3.0×10\^9 /L;

⁃ Neutrophil count ≥1.5×10\^9 /L;

⁃ Lymphocyte count ≥ 0.5 × 10\^9 /L;

⁃ Hemoglobin ≥90 g/L;

⁃ Platelet count ≥75×10\^9 /L;

⁃ Serum total bilirubin ≤2.0× upper limit of normal (ULN);

⁃ Aspartate aminotransferase (AST), alanine aminotransferase (ALT) ≤2.5× ULN; For patients with liver metastases or primary liver tumor lesions, aspartate aminotransferase and alanine aminotransferase should be ≤5×ULN; for patients with a history of Gilbert syndrome/suspected Gilbert syndrome, total bilirubin (TBIL) should be ≤3×ULN;

⁃ Creatinine \<1.5×ULN and endogenous creatinine clearance ≥50 mL/min (creatinine clearance Cockcroft-Gault method: creatinine clearance for men = \[(140-age)×body weight (kg)\]/\[0.818×creatinine (umol/L)\]; creatinine clearance for women = \[(140-age)×body weight (kg)×0.85\]/\[0.818×creatinine (umol/L)\]).

• Good lung function, with basic finger saturation ≥ 95% in indoor air environment;

• Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1;

⁃ Female subjects of childbearing age must undergo a serum pregnancy study with negative results at screening and before purging, and be willing to use medically approved highly effective contraceptive methods during the study and for at least 1 year after the last study treatment. Male subjects whose partners are female subjects of childbearing age should undergo surgical sterilization or agree to use effective contraceptive methods during the study and for at least 1 year after the last study treatment, and are prohibited from donating sperm within 1 year.

⁃ Venous access can be established, and peripheral blood mononuclear cell collection can be performed at the investigator's discretion.