Inclusion Criteria:

          -  1. Histopathologically confirmed breast cancer. 2. Hormone receptor(HR) positive and
             human epidermal growth factor receptor-2 (HER2) negative for primary or metastatic
             tumors confirmed by immunohistochemistry test.

             3. Agree to provide at least 10 unstained sections of tumor tissue obtained within 2
             years (surgery or biopsy) for genetic mutation detection and with PIK3CA mutation
             positive.

             4. Age ≥18 years, postmenopausal women. 5. Inoperable, locally advanced recurrent
             and/or metastatic tumor, and has at least one measurable lesion.

             6. Inappropriate to receive radical resection or radiation therapy. 7. Eastern
             Cooperative Oncology Group (ECOG) performance status score of 0 to 1.

             8. Life expectancy ≥12 weeks. 9. Male or female subjects should agree to use an
             adequate method of contraception starting with the first dose of study therapy through
             6 months after the last dose of study.

             10. Understood and signed an informed consent form.

        Exclusion Criteria:

          -  1. Has known untreated or active CNS metastasis. 2.Previous or co-existing cancers of
             a different site or histology from primary breast cancer.

             3. Inadequate bone marrow hematopoiesis. 4. Abnormal liver function. 5. Renal
             abnormalities. 6. Has bleeding risk. 7. Gastrointestinal disorder. 8.
             Cardio-cerebrovascular anomaly. 9. Previous treatment: A) Has received fulvestrant
             injection; B) Has received PI3K, AKT and mTOR inhibitors; C) Has received anti-tumor
             treatment, including chemotherapy, radiotherapy, hormone therapy, biotherapy,
             immunotherapy, and surgical treatment, less than 4 weeks after the first
             administration; D) Has received oral targeted drugs less than 5 half-lives to the
             first administration; E) Has received palliative radiotherapy for non-target lesions
             within 2 weeks before the first administration; F) Toxicity related to previous
             anti-tumor treatment did not recover to ≤ grade 1, except for hair loss.

             10.Has participated in other clinical trials within 30 days. 11.Has received major
             surgical treatment within 1 month or unhealed traumatic injury.

             12. Has a history of organ transplantation or hematopoietic stem cell transplantation
             within 60 days prior to the first administration.

             13.Immunosuppressant or systemic or absorbable local hormone therapy is required to
             achieve the aim of immunosuppression (dose > 10mg/ day prednisone or other
             therapeutic hormones) and is still used within 2 weeks after the first administration.

             14.Active bacterial or fungal infections diseases. 15.Human immunodeficiency virus
             (HIV) infection. 16.Pregnant or lactating female patients. 17.Has mental and
             neurological diseases. 18. With severe or poorly controlled diseases. 19. Has a
             history of active tuberculosis. 20. Patients have inadequate compliance to participate
             in this study.