To Evaluate the Efficacy and Safety of TQB3616 in Combination With Fulvestrant Versus Placebo in Combination With Fulvestrant in Previously Untreated Hormone-receptor (HR)-Positive, Human Epidermal Growth Factor Receptor 2 (HER2)-Negative Advanced Breast Cancer

Exclusion Criteria

• •Associated diseases and history：
• •1. The presence or current co-occurrence of other malignant tumors within 5 years, except ured cervical carcinoma in situ, non-melanoma skin cancer, and superficial bladder tumors \[Ta (non-invasive tumor), Tis (carcinoma in situ), and T1 (tumor infiltrating basal membrane)\];
• •2. Multiple factors affecting oral and drug absorption (such as inability to swallow, post-gastrointestinal resection, ulcerative colitis, symptomatic/inflammatory bowel disease, chronic diarrhea and intestinal obstruction);
• •3. Patients with a history of severe pneumonia such as interstitial lung disease;
• •4. Unrelieved toxicity higher than GRADE 1 Common Terminology Criteria for Adverse Events (CTCAE) due to any previous anti-tumor treatment, hair loss is not included;
• •5. Major surgery or significant traumatic injury within 28 days prior to randomization;
• •6. Long-term unhealed wounds, ulcers or fractures;
• •7. Occurrence of arteriovenous/venous thrombosis events within 6 months, such as cerebrovascular accident (including transient ischemic attack, cerebral hemorrhage, cerebral infarction), deep vein thrombosis and pulmonary embolism, etc.;
• •8. History of psychotropic drug abuse and can't get rid of it or with mental disorders;
• •9. Subject with any severe and/or uncontrolled disease, including：
• •1. Arrhythmias requiring treatment with grade≥2 myocardial ischemia, myocardial infarction, and congestive heart failure (NYHA(New York Heart Association) classification) within 6 months prior to study enrollment (including qtc≥480ms during screening period); And uncontrolled high blood pressure;
• •2. Active or uncontrolled severe infection (≥CTCAE grade 2 infection) or unexplained fever \> 38.5℃ within 28 days prior to randomization;
• •3. Decompensated cirrhosis (Child-Pugh liver function score B or C), active hepatitis ;
• •4. Patients with renal failure requiring hemodialysis or peritoneal dialysis;
• •5. A history of immunodeficiency, including HIV ( Human Immunodeficiency Virus) positive or other acquired or congenital immunodeficiency diseases, or a history of organ transplantation or hematopoietic stem cell transplantation;
• •Tumor-related symptoms and treatment；
• •1. Visceral crisis exists;
• •2. Severe bone injury due to bone metastasis of tumor;
• •3. Received radiotherapy (except palliative radiotherapy for non-target lesions) and other anti-tumor therapies (the washout period was calculated from the end of the last treatment) within 2 weeks prior to randomization;
• •4. Prior medical treatment with fulvestrant, everolimus or CDK4/6 inhibitor;
• •5. The presence of clinically uncontrolled pleural, ascites and pericardial effusion requiring repeated drainage or medical intervention (14 days prior to randomization);
• •Known allergy to fulvestrant, Luteal Hormone Releasing Hormone (LHRH) agonists (e.g. Goserelin), TQB3616/ placebo or any supplement;
• •History of live attenuated vaccine vaccination within 28 days prior to randomization or planned live attenuated vaccine vaccination during the study period;
• •Participated in clinical trials of other antitumor drugs within 4 weeks pior to randomization;
• •With other serious physical or mental diseases or abnormal laboratory tests that may increase the risk of study participation or interfere with the study results, or unsuitable for the study for other reasons considered by investigators.