TQB3909 is an inhibitor targeting B-cell lymphoma (BCL)-2 protein. By binding to BCL-2 protein, TQB3909 releases Pro apoptotic proteins such as BCL-2-Anatagonist/Killer 1(BAK), BCL-2 associated X (BAX) protein and BCL-2 associated death (BAD) protein, promotes the release of cytochrome c from mitochondria, phosphatidylserine eversion, stimulates caspase 3/7 activity and caspase 3/9 cleavage, and induces apoptosis.

Inclusion Criteria:

• Evidence of a personally signed and dated informed consent document indicating that the patient has been informed of all pertinent aspects of the study.
• Age: 18 to 75 years old; female patient, an Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1.
• Histopathologically confirmed HR positive and HER2 negative advanced or metastatic breast cancer.
• Patients who have been treated with endocrine therapy and have experienced disease progression.
• Patients previously treated with any CDK4/6 inhibitor and not treated with BCL-2 inhibitor.
• Has at least one measurable lesion according to Response Evaluation Criteria In Solid Tumors (RECIST) v1.1 criteria
• The main organs function well;
• Female patient had no plans to become pregnant and voluntarily took effective contraceptive measures from agree with the study to at least 6 months after the last dose of study drug.

Exclusion Criteria:

• 1. Concomitant disease and medical history:

  1. There were other malignant tumors in 3 years before the first medication.
  2. Has multiple factors affecting oral medication;
  3. Unalleviated toxicity ≥ grade 1 due to any previous therapy;
  4. Major surgical treatment, open biopsy and obvious traumatic injury were performed within 28 days before the study; e．Arteriovenous thrombotic events occurred within 6 months before the first medication, such as cerebrovascular accident (including transient ischemic attack, cerebral hemorrhage, cerebral infarction), deep venous thrombosis and pulmonary embolism; f．Have a history of psychotropic drug abuse and can not quit or have mental disorders; g．Subjects with any severe and / or uncontrolled disease included: Cirrhosis, active hepatitis, history of immunodeficiency;

• Tumor-related symptoms and treatment:

  1. Has central nervous system metastases (CNS) and/or cancerous meningitis or leptomeningeal carcinomatosis;
  2. have received radiotherapy, other antineoplastic therapy within 2 weeks prior to the first dose;
  3. Has uncontrollable pleural effusion, pericardial effusion, or ascites requiring recurrent drainage procedures.

• Known hypersensitivity to TQB3909, LHRH agonists (e.g., goserelin), or any excipients.

• Subjects who have received the vaccine within 28 days prior to the first dose, or are planning to receive the vaccine during the study period.

• Has Participated in other clinical trials within 4 weeks before first dose.

• According to the judgement of the investigators, there are other factors that may lead to the termination of the study.

female patient aged from 18 to 75 years old, with an Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1.