The primary objective of this study is to compare progression-free survival (PFS) of patients with metastatic triple-negative breast cancer randomised to treatment with standard chemotherapy plus moxifloxacin or placebo.

This is a multicenter, randomised, double-blind, placebo-controlled, phase 3 trial. The main purposes of this study are to examine the efficacy and safety of standard chemotherapy plus moxifloxacin or placebo as first-line treatment in patients with metastatic triple-negative breast cancer. This study is designed to recruit up to 228 subjects.

Inclusion Criteria:

• Eastern Cooperative Oncology Group (ECOG) score of 0 to 1.
• Histologically confirmed invasive ductal carcinoma, no specific type (NOS)
• ER negative and progesterone receptor (PR) negative (defined as < 1% positive cells by IHC), human epidermal growth factor receptor 2 (HER2) negative (defined as IHC 0-1 staining or fluorescent in situ hybridization (FISH) negative).
• No prior therapy after first recurrence or diagnosis of metastatic disease.
• At least 1 measurable lesion as defined by Response Evaluation Criteria in Solid Tumors (RECIST) criteria.
• Neutrophil-to-lymphocyte ratios (NLR) in peripheral blood ≥ 2.
• Adequate organ function including bone marrow, renal function, hepatic function, and cardiac reserve (Left ventricular ejection fraction (LVEF) by echocardiogram ≥45%).
• Compliance with the study protocol.
• Have provided written and signed informed consent.

Exclusion Criteria:

• Pregnant or breast feeding.
• Definitive breast cancer susceptibility gene (BRCA) mutation, Programmed Cell Death-Ligand 1 (PD-L1) positive, microsatellite instability-high (MSI-H), and mismatch repair deficient (dMMR).
• Patients who are receiving or will receive other biological agents or immunotherapy.
• Uncontrolled medical problems.
• Evidence of active acute or chronic infection.
• Hepatic, renal, cardiac, or bone marrow dysfunction as detailed above.
• Concurrent malignancy or history of other malignancy within the last five years.
• Known severe hypersensitivity to moxifloxacin
• Patients were unable or unwilling to comply with program requirements.