A Study of XZP-3287 in Combination With Letrozole/Anastrozole in Patients With Advanced Breast Cancer

Inclusion Criteria:

1. Female patients aged ≥18 years and ≤75 years old;

2. Patient is in the menopausal state；

3. Histologically or cytologically confirmed locally advanced, recurrent or metastaticbreast cancer, which was pathologically confirmed to be HR-positive andHER2-negative;

4. Evidence of locally advanced, recurrent, or metastatic disease that is not amenableto curative surgical resection or radiation therapy and is not clinically amenableto chemotherapy;

5. No prior systemic anticancer therapy for locally advanced, recurrent, or metastaticdisease;

6. At least one measurable lesion (based on RECIST v1.1) or only bone metastases;

7. Patient has an Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1;

8. Adequate organ and marrow function;

9. Patient of childbearing age must undergo a serum pregnancy test within 7 days beforerandomization, and the result is negative; patient is willing to use a medicallyapproved high-efficiency contraceptive method during the study period and within 6months after the last study drug treatment;

10. Patient with acute toxic reactions caused by previous anti-tumor treatments orsurgical operations were alleviated to grade 0 to 1 (NCI-CTCAE v5.0), or to thelevel specified by the enrollment criteria;

11. Patient has signed informed consent before any trial related activities.

Exclusion Criteria:

1. Patients with disease recurrence or metastasis at or within 12 months after previousneoadjuvant or adjuvant therapy with endocrine drugs;

2. Patient with visceral crisis or brain metastases, except for patient with stablebrain metastases;

3. Patient had clinically significant pleural effusions, ascites effusions, orpericardial effusions in the 4 weeks before enrollment;

4. Patient who received prior treatment with mTOR inhibitors or CDK4/6 inhibitors ;

5. Participation in a prior treatment of major surgery, chemotherapy, radiotherapy, andany anti-tumor treatment within 14 days before enrollment；

6. Patient who participated in other clinical trials within 14 days before enrollmentor within 5 half-lives of the trial drug, whichever is longer;

7. Patient used CYP3A4 potent inhibitors or potent inducers within 14 days beforeenrollment or within 5 half-lives of the drug, whichever is longer;

8. Initiation of bisphosphonates or RANKL inhibitors within 7 days before enrollment,and subjects who have initiated treatment > 7 days before enrollment should notchange the method of use;

9. Any other malignant tumor has been diagnosed within 5 years before randomization;

10. Patient is in the active stage of HBV, HCV or co-infected with HBV, HCV, or Patientwith positive HIV antibody;

11. Patient with severe infection within 4 weeks before enrollment, or unexplainedfever> 38.3℃ during screening/before enrollment;

12. Patient with heart function impaired or clinically significant heart disease within 6 months before enrollment;

13. Cerebrovascular accident occurred within 6 months before enrollment, includinghistory of transient ischemic attack or stroke; pulmonary embolism;

14. Inability to swallow, intestinal obstruction or other factors that affect the takingand absorption of the drug;

15. Patient with a known hypersensitivity to any of the excipients in this study;

16. A prior history of autologous or allogeneic hematopoietic stem cell transplantation;

17. A prior history of psychotropic drug abuse or drug use;

18. Nursing Mothers;

19. The researchers considered that there were some cases that were not suitable forinclusion.