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

This is a Phase III, double-blind, randomized multicenter study to compare the efficacy and to evaluate the safety and immunogenicity of HLX02 and European Union (EU)-sourced Herceptin® in patients with human epidermal growth factor receptor 2 (HER2)-positive, recurrent or previously untreated metastatic breast cancer. Eligible patients will be assessed centrally for HER2 status and the presence of at least one measurable target lesion before randomization. Patients will undergo a tumor assessment for evaluation of response according to Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST 1.1) every 6 weeks up to 24 weeks (regardless of the number of cycles actually given); thereafter, assessments will be done every 9 weeks (after Cycles 11, 14, and 17) or earlier in the case of clinical signs of progression.