['breast cancer']
['chidamide', 'exemestane', 'placebo']

        Inclusion Criteria:

          1. 18 ~ 75 years old, postmenopausal women;

          2. Histological or cytological confirmation of hormone receptor-positive [estrogen
             receptor (ER) positive and progesterone receptors (PgR) positive or negative] breast
             cancer;

          3. Disease progression or recurrence after at least one endocrine therapy (either in
             advanced/metastatic setting or adjuvant setting);

          4. ≤4 prior therapies (either in advanced/metastatic setting or adjuvant setting),
             patients may have received one prior chemotherapy;

          5. The disease condition is inoperable, stage III or stage IV, at least one measurable
             lesion or simple bone metastases with no measurable lesions;

          6. Last prior therapy intervals: (a) if the last treatment was endocrine therapy, the
             interval must ≥ 2 weeks; (b) if the last treatment was chemotherapy therapy, the
             interval must ≥ 4 weeks;

          7. Eastern Cooperative Oncology Group Performance Status: 0~1;

          8. Absolute neutrophil count ≥ 1.5×109 / L, platelet count ≥ 100×109 / L, hemoglobin ≥ 90
             g/L;

          9. Life expectancy ≥ 3 months;

         10. Have signed informed consent.

        Exclusion Criteria:

          1. Patients have known central nervous system (CNS) metastases or a history of CNS
             metastases , or with leptomeningeal disease;

          2. Patients with human epidermal growth factor receptor-2 (Her-2) positive;

          3. Patients previously received treatment with exemestane;

          4. Patients received radiotherapy ≤ 4 weeks prior to study entry;

          5. Patients with no measurable lesion (except simple bone metastasis), such as pleural or
             pericardial effusion, ascites, et al;

          6. Patients have uncontrolled or significant cardiovascular disease, including:

               1. Myocardial infarction (< the last 12 months)

               2. Uncontrolled angina (< the last 6 months)

               3. Congestive heart failure (< the last 6 months), or Left Ventricular Ejection
                  Fraction (LVEF) < 50% prior to study entry

               4. History of any significant ventricular arrhythmias (e.g., ventricular
                  tachycardia, ventricular fibrillation, or TdP)

               5. History of significant QT interval prolongation, or Corrected QT Interval (QTc) >
                  450 ms prior to study entry

               6. History of cerebrovascular accident

               7. Symptomatic coronary heart disease requiring treatment with agents

          7. The size of fluid area detected by cardiac ultrasonography in cavum pericardium is
             ≥10mm during diastolic period;

          8. History of organ transplantation;

          9. Patients have not recovered from all clinically relevant toxicities to grade 1 due to
             prior therapies;

         10. Patients have clinical significant gastrointestinal abnormality, e.g., unable to
             swallow, chronic diarrhea, ileus, that would interfere the ingestion,transportation or
             absorption of oral agents;

         11. Active infection [Suffered from active infection of bacteria, virus, fungi,
             mycobacteria, parasites, or other infections (excluding nail bed fungal infections),
             or require intravenous antibiotic therapy, or antiviral therapy, or hospitalization
             due to any significant infection events], or persistent fever within 14 days prior to
             study entry;

         12. Patients had organ surgery < 6 weeks prior to study entry;

         13. Abnormal liver function [total bilirubin > 1.5×upper limit of normal (> 3×upper limit
             of normal in case of Gilbert syndrome); Transaminases (ALT, AST) >2.5×upper limit of
             normal (>5x upper limit of normal patients with liver metastases), abnormal renal
             function (serum creatinine > 1.5×upper limit of normal);

         14. Patients with prior invasive malignancies with the exception of curatively-treated
             basal cell or squamous cell carcinoma of the skin or cervical carcinoma in situ,
             unless received curative treatment and with documented evidence of no recurrence in
             the past five years;

         15. Any mental or cognitive disorder, that would interfere the ability to understand the
             informed consent document or the operation and compliance of study;

         16. Patients are currently enrolled in another investigational drug study, or completed
             within 4 weeks prior to study entry, with the exception of patients only in overall
             survival follow-up;

         17. Any other condition which is inappropriate for the study in the opinion of the
             investigators.
      