• 1\) adult female patients (aged 18-70 years) with metastatic triple negative breast cancer confirmed by pathology or imaging;

• 2\) no more than two previous lines of therapy for metastatic disease;

• 3\) ECOG performance status ≤2 and expected survival time ≥ 3 months;

• 4\) At least one measurable lesion on imaging within 2 weeks before enrollment; Or simple bone metastases;

• 5\) Prior treatment-related toxicity at enrollment had to be resolved to NCI CTCAE version 5.0 ≤ grade 1 (excluding alopecia or any other toxicity deemed by the investigator to be of no risk to patient safety)

• 6\) adequate bone marrow reserve: a. White blood cell count (WBC) ≥3.0×10\^9 / L, b. Neutrophil count (ANC) ≥1.5×10\^9 / L, c. Platelet count (PLT) ≥70×10\^9 / L

• 7\) liver, kidney and heart function tests were basically normal (according to the normal values of the laboratories in the study center) : a. Total bilirubin (TBIL) ≤3× upper limit of normal value (ULN), b. alanine aminotransferase and aspartate aminotransferase (ALT/AST) ≤2.5×ULN (≤5xULN in patients with liver metastases), c. Total bilirubin (TBIL) ≤3× upper limit of normal value (ULN), B. alanine aminotransferase and aspartate aminotransferase (Alt /AST) ≤2.5×ULN (≤5xULN in patients with liver metastases). Serum creatinine ≤1.5×ULN or creatinine clearance (Ccr) ≥60 ml/min; d. Left ventricular ejection fraction (LVEF) ≥ 55%, e. QTcF(Fridericia correction) ≤ 470 ms.

• 8\) understood the study process and volunteered to participate in the study. Informed consent was signed.