Sacituzumab Tirumotecan Plus Tagitanlimab in Previously Treated Locally Advanced or Metastatic Triple Negative Breast Cancer

Key inclusion criteria include but are not limited to: * Age ≥ 18 years at the time of signing informed consent. * Histologically and/or cytologically confirmed triple-negative breast cancer (TNBC) based on the most recent biopsy or other pathological specimens, including: 1. Definition of human epidermal growth factor receptor 2 (HER2) negative: immunohistochemistry (IHC) of 0 or 1+; if HER2 is 2+ by IHC, negative HER2 expression must be confirmed by fluorescencein situ hybridization (FISH); Estrogen and progesterone receptor negative means that less than 1% of the cells express hormone receptors as indicated by IHC. 2. Tumor stage: locally advanced, recurrent, or metastatic TNBC; locally advanced cases must be confirmed by the investigator as unsuitable for curative surgical resection. * Patients with unresectable locally advanced or metastatic triple-negative breast cancer: 1. Those who have received chemotherapy combined with a PD-(L)1 inhibitor as first-line treatment for locally advanced or metastatic disease and experienced progression ≥ 3 months later. 2. Those who received chemotherapy combined with a PD-(L)1 inhibitor in the neoadjuvant and/or adjuvant setting and experienced recurrence or disease progression to unresectable locally advanced or metastatic disease ≥ 3 months later but within 12 months. 3. Those who received chemotherapy combined with a PD-(L)1 inhibitor in the neoadjuvant and/or adjuvant setting and experienced recurrence or disease progression to unresectable locally advanced or metastatic disease after ≥ 12 months, and have subsequently progressed on first-line treatment for locally advanced or metastatic disease. * Newly diagnosed brain metastases at screening must be stable for ≥ 4weeks after local treatment (e.g., radiotherapy) with imaging confirmation. * The most recent tumor tissue sample from the primary and/or metastatic lesion must show a PD-L1 combined positive score (CPS) ≥ 1. * Patients must have at least one measurable lesion per RECIST v1.1 criteria; those with only skin or bone lesions cannot be included. * Eastern Cooperative Oncology Group (ECOG) performance status of 0 to1. * Patients must have adequate organ and bone marrow function (no blood transfusion, recombinant human thrombopoietin, or colony stimulating factor therapy has been received within 2 weeks prior to the treatment) * Patients of childbearing potential (male or female) must use effective medical contraception from consent until 6 months after the end of the dosing period. Key exclusion criteria include but are not limited to: * Previously received any of the following treatments (including in the adjuvant or neoadjuvant setting): 1. Targeted TROP2 therapy. 2. Any drug treatment targeting topoisomerase I, including antibody drug conjugates (ADC) therapy. * Known to have meningeal metastasis, brainstem metastasis, spinalcord metastasis, and/or compression, active central nervous system(CNS) metastasis. Patients with previously treated brain metastases canparticipate if clinically stable for at least 4 weeks before dosing and do not require corticosteroids or anticonvulsants for at least 14 days. Patients with untreated asymptomatic brain metastases must require investigator approval. * Has a history of documented severe dry eye syndrome, severe Meibomian gland disease and/or blepharitis, or corneal disease that prevents/delays corneal healing. * Within 3 years before administration having other malignancies (except forthose cured by local treatment, such as basal cell carcinoma of the skin,squamous cell carcinoma of the skin, cervical carcinoma in situ, etc.). * Has uncontrolled, significant cardiovascular disease or risk factors, uncontrollable systemic diseases. * Presence of steroid-requiring (non-infectious) interstitial lung disease (ILD)or a history of non-infectious pneumonia, currently having ILD or non-infectious pneumonia, or suspected ILD or non-infectious pneumonia that cannot be ruled out by imaging at screening. * Unresolved toxicities from previous anti-tumor therapy to ≤ Grade 1 (based on NCI CTCAE v5.0) or the level specified in the inclusion and exclusion criteria. * Patients with active chronic inflammatory bowel disease, gastrointestinal obstruction, severe ulcers, gastrointestinal perforation, abdominal abscess, or acute gastrointestinal bleeding. * Having an active autoimmune disease requiring systemic treatment inthe past two years. * Known active tuberculosis, hepatitis B or hepatitis C. * Human Immunodeficiency Virus (HIV) test positive or history of Acquired Immunodeficiency Syndrome (AIDS); known active syphilis infection. * Known allergy to the study drug or any of its components, known history of severe hypersensitivity to other biological products * Pregnant or breastfeeding women.