A Phase II Clinical Study Evaluating Entinostat With or Without Anlotinib + Fulvestrant for the Treatment of Hormone Receptor (HR) -Positive, Human Epidermal Growth Factor Receptor-2 (HER-2) -Negative Advanced Breast Cancer That Relapsed or Progressed After Endocrine Therapy

* This study was an open, multicenter phase II clinical trial that enrolled 118 patients with HR+/HER2- with recurrent or progressive advanced breast cancer treated with CDK4/6 inhibitors; * The study adopted the Simon phase 2 design, and all 20 eligible patients were treated with entinostat + fulvestrant; The study was terminated if no more than 2 patients achieved objective response and continued to enter Phase 2 if no more than 3 patients achieved objective response. In Phase 2, qualified patients were randomly assigned at a ratio of 1:1.5 to either the entestasta + fluvestrus group (Group 1) or the anlotinib + entestasta + fluvestrus group (Group 2), with 39 patients enrolled in group 1 and 59 patients enrolled in group 2; All patients were treated until the subjects' treatment would continue until the subjects experienced disease progression, intolerable toxicity, active withdrawal from treatment, or other conditions specified in the protocol, whichever occurred first. * During the study period, efficacy evaluations will be conducted every 8 weeks in accordance with the Solid Tumor Efficacy Evaluation Criteria (RECIST) v1.1 until disease progression, the initiation of a new anti-tumor treatment by the subject, or the withdrawal of informed consent, whichever occurs first. * Continuous safety evaluations will be conducted during the study treatment period. All subjects who have received at least one study treatment will be required to undergo end-of-treatment visits and safety follow-up visits within 7 days and 30±2 days after the last study treatment, respectively. * The end of the study was defined as the occurrence of disease progression or the end of the study treatment in all subjects, or the early termination of the study for other reasons, whichever occurred first.