Inclusion Criteria:
* 1\. Age: 18-75 years (Whichever is on the day of signing the informed consent form).
* 2\. Subjects have histologically or cytologically confirmed breast cancer at unresectable，recurrent/metastatic stage, with the requirements below based on the most recent pathological report:
1. HER2-negative confirmed by histological or cytological testing;
2. Pathological report is available to confirm HR status.
* 3\. Assessed by the Investigator as suitable for single-agent docetaxel therapy.
* 4\. At least one extracranial measurable lesion at baseline according to RECIST 1.1 criteria.
* 5\. Has adequate organ and system functions within 7 days prior to the first dose.
* 6\. Eastern Cooperative Oncology Group performance status of 0 or 1.
* 7\. Expected survival ≥ 3 months.
Exclusion Criteria:
* 1\. Has received prior taxane-containing single-agent or combination regimens, and have disease progression during salvage therapy for unresectable locally advanced or metastatic breast cancer (has received at least 2 cycles), or developed recurrent-metastatic disease within 12 months following adjuvant therapy.
* 2\. History of severe allergy or hypersensitivity reactions (Grade ≥3 per NCI-CTCAE Version 6.0) to human serum albumin or docetaxel and/or contraindications thereto, or history of severe allergy and/or contraindications to glucocorticoids.
* 3\. Untreated active brain metastases (including brain or leptomeningeal metastases). Subjects with treated brain metastases may be enrolled if lesions are stable without evidence of new or enlarging pre-existing brain metastases.
* 4\. With a history of other primary malignant tumors within 5 years before administration.
* 5\. Presence of serous cavity effusion requiring drainage or diuretic therapy within 2 weeks prior to the first dose.
* 6\. Severe neurological diseases (e.g., epilepsy, dementia, etc.) and Grade ≥2 peripheral neuropathy.
* 7\. Receipt of systemic glucocorticoid therapy within 14 days prior to the first dose.
* 8\. Current clinically significant abnormal interstitial lung disease.
* 9\. History of severe cardiovascular and cerebrovascular diseases within 6 months prior to the first dose.
* 10\. Has arterial or venous thromboembolism (e.g., lower-extremity deep vein thrombosis, lower-extremity arterial embolism, pulmonary embolism, etc.) within 6 months prior to the first dose. Stable thrombus is permitted for enrollment if the Investigator assesses no associated cardiovascular risk.
* 11\. Severe chronic or active infection requiring intravenous antibacterial, antifungal, or antiviral therapy within 2 weeks prior to the first dose.
* 12\. Has undergone major visceral organ surgery (excluding puncture biopsy or infusion device implantation) within 4 weeks prior to the first dose, or who require major visceral organ surgery during the study period.
* 13\. Receipt of chemotherapy, targeted therapy, immunotherapy, endocrine therapy, or other investigational study drug within 4 weeks or 5 half-lives prior to the first dose (whichever is shorter, with a minimum of 2 weeks); receipt of radiotherapy within 2 weeks prior to the first dose; receipt of traditional Chinese medicine with anti-tumor indications within 2 weeks prior to the first dose.
* 14\. Toxicities from all prior anti-tumor therapies have not recovered to Grade 1 or less prior to the first dose.
* 15\. Has received powerful CYP3A4 inhibitor or inducer within 2 weeks before the first dose.
* 16\. Has active hepatitis B infection, hepatitis C infection, positive HIV antibody, or active syphilis.
* 17\. Concurrent participation in another interventional clinical study.
* 18\. Any other conditions that, in the Investigator's opinion, render the participant unsuitable for participation in this clinical trial.
