A Study of SHR-A1811 and Fulvestrant, With or Without HS-10352, in Locally Advanced or Metastatic Breast Cancer Patients

Inclusion Criteria: 1. Female patients aged ≥18 years and ≤75 years; 2. ECOG Performance Status of 0 -2; 3. Locally advanced/metastatic breast cancer not amenable to curative therapy 4. Disease progression during treatment or within 12 months of completing adjuvant therapy ; 5. No prior anti-cancer systemic therapy has been administered; 6. Fasting blood glucose \< 126 mg/dL, and HbA1C \< 6.0%; 7. Life expectancy of ≥3 months; 8. Patients have at least one target lesion according to RECEST 1.1; 9. Adequate function of major organs; 10. Female patients who are either premenopausal or have not undergone surgical sterilization: during the treatment period and for at least 7 months after the final dose of study medication, agree to abstain from sexual activity or utilize effective contraceptive methods. 11. Sign Informed Consent Form. Exclusion Criteria: 1. Breast cancer that has not been histologically confirmed; 2. Inflammatory breast cancer; 3. Participants ineligible for endocrine therapy due to any disease burden, as judged by the investigator; 4. Meningeal metastasis or active parenchymal brain metastasis; 5. Presence of diabetes symptoms, history of primary diabetes, gestational diabetes, steroid-induced diabetes, or other secondary diabetes; 6. Prior anti-cancer systemic therapy has been administered; 7. Use of investigational drugs within 4 weeks； 8. Received immunotherapy, macromolecular targeted therapy, or other antitumor biologics within 4 weeks; or received endocrine therapy, chemotherapy, small molecule targeted drug therapy, or traditional Chinese medicine treatment with antitumor indications within 2 weeks; 9. Received radical radiotherapy within 4 weeks, or received palliative radiotherapy within 2 weeks; 10. Previously received antitumor treatment or radiotherapy for any malignancy, excluding malignancies such as cured cervical carcinoma in situ, basal cell carcinoma, or squamous cell carcinoma; 11. A history of other malignancies within the past 5 years, excluding cured cases of skin basal cell carcinoma and cervical carcinoma in situ; 12. Prior anti-tumor treatment toxicities have not yet recovered to NCI CTCAE V5.0 grade ≤1 or baseline levels; 13. A history of immunodeficiency, including HIV positivity, other acquired or congenital immunodeficiency diseases, or a history of organ transplantation; 14. Interstitial pneumonia/interstitial lung disease, or presence of moderate to severe pulmonary disease that may interfere with the detection or management of drug-related pulmonary toxicity within 3 months prior to the first administration of the study drug, as well as any autoimmune, connective tissue, or inflammatory diseases involving the lungs, or a history of total pulmonary resection surgery 15. Presence of active hepatitis B, hepatitis C, liver cirrhosis, or severe infections requiring control with antibiotics, antiviral drugs, or antifungal medications; 16. History of hereditary or acquired bleeding and thrombotic tendencies (such as haemophilia, coagulation disorders, etc.); 17. Inability to swallow, intestinal obstruction, or the presence of other factors affecting drug intake and absorption; 18. Patients with known allergies or contraindications to the study drug and its excipient components; 19. Female patients who are pregnant or lactating, those of reproductive potential with a positive baseline pregnancy test, or those of reproductive age who are unwilling to use effective contraceptive measures throughout the entire study period; 20. According to the investigator's judgment, patients with severe concomitant diseases that pose a risk to their safety or prevent them from completing the study, a history of definite neurological or psychiatric disorders, including epilepsy or dementia, or any other condition deemed by the investigator to make the patient unsuitable for participation in this study.