Compare Efficacy, Safety and Immunogenicity of HLX02 and Herceptin in Previously Untreated HER2 +Overexpressing Metastatic Breast Cancer

Inclusion Criteria

• Patients have voluntarily agreed to participate and given written informed consent.
• Male or female ≥18 years of age on day of signing the informed consent form (ICF).
• Histologically or cytologically confirmed adenocarcinoma of the breast.
• Recurrent disease not amenable to curative surgery or radiation therapy, or metastatic disease with an indication for a taxane-containing therapy.
• Availability of formalin-fixed paraffin-embedded (FFPE) tissue block from the primary tumor, or a metastatic lesion, to confirm HER2-positivity by the central laboratory, based on FISH amplification ratio ≥2.0 or IHC score 3+, and for hormone status (ER/PgR) determination (local or central laboratory). If not possible, a fresh biopsy is required.
• No prior systemic anticancer agent such as chemotherapy, biological or targeted agent for metastatic disease with the exception of hormonal therapy, which must be stopped at least 2 weeks before randomization. Use of herbal remedies or traditional Chinese medicines for anticancer, hematologic or liver function, or anti-infective treatment must be stopped at the time of the ICF signature (at least 2 weeks before randomization).
• For patients with recurrent disease, prior neo-/adjuvant therapy containing trastuzumab and/or lapatinib must have been stopped at least 12 months before the diagnosis of recurrent (local or metastatic) disease. If trastuzumab/lapatinib was not used, prior neo-/adjuvant therapy with a taxane must have been stopped at least 6 months before the diagnosis of recurrent (local or metastatic) disease. If only other cytotoxics were given, they must be stopped at least 4 weeks before randomization. Any hormonal therapy must be stopped at the time of the ICF signature.
• Measurable disease (at least one measurable target lesion assessed by CIR; bone-only or central nervous system [CNS]-only metastases are not allowed).
• Eastern Cooperative Oncology Group (ECOG) performance status of 0-1.
• LVEF within institutional range of normal at baseline (within 42 days before randomization) as determined by either echocardiography (ECHO) or multigated acquisition (MUGA) scan.
• Adequate hematologic, hepatic and renal function as indicated by the following laboratory values:
• Absolute neutrophil count (ANC) ≥1, 500/μL without granulocyte-colony stimulating factor (G-CSF) or other medical support
• Platelets ≥100,000/μL
• Hemoglobin ≥9 g/dL without transfusion or other medical support within 14 days
• Serum creatinine ≤1.5 x upper limit of normal (ULN) and creatinine clearance rate ≥50 mL/min, calculated according to Cockroft-Gault formula
• Serum total bilirubin ≤1.5 x ULN (unless the patient has documented ·Gilbert's syndrome) without any medical support within 14 days
• Serum aspartate aminotransferase/glutamicoxaloacetic transaminase (AST/SGOT) or serum alanine aminotransferase/glutamate-pyruvate transaminase (ALT/SGPT) ≤2.5 x ULN (≤5 x ULN in the case of liver metastases) provided alkaline phosphatase (ALK) is ≤2.5 x ULN. In the case of bone metastasis, serum ALK can be >2.5 x ULN if AST and ALT are ≤1.5 x ULN without any medical support within 14 days
• International normalized ratio (INR), and activated partial prothrombin time (aPTT) or partial prothrombin time (PTT) ≤1.5 x ULN.
• Estimated life expectancy ≥3 months.
• Female patients are eligible to enter and participate in the study if they are of: Non-childbearing potential. Childbearing potential, have a negative serum pregnancy test at Screening, are not breast feeding, and use highly-effective or acceptable contraceptive measures before study entry and throughout the study until 7 months after the last investigational/comparator product administration. Highly-effective or acceptable contraceptive measures.
• Male patients with partners of childbearing potential are eligible to enter and participate in the study if they, and their female partners, are willing to use highly-effective or acceptable contracepti