Trastuzumab Biosimilar (HLX02), Pertuzumab Plus Chemotherapy in Patients with HER2-Positive Metastatic Breast Cancer after Progression of Trastuzumab: A Prospective, Phase II Study

Purpose This study aims to evaluate the efficacy and safety of trastuzumab biosimilar (HLX02) in combination with pertuzumab and chemotherapy in patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC) after progression of trastuzumab. Materials and Methods In this prospective, single-arm, phase II study, patients with HER2-positive MBC after progression of trastuzumab received pertuzuamb, HLX02, and chemotherapy in Beijing Cancer Hospital from March 2020 to December 2022. The primary endpoint was progression-free survival (PFS), and secondary endpoints included objective response rate (ORR), disease control rate (DCR), overall survival (OS), and safety. The study was registered with ClinicalTrials.gov (NCT05188495). Results A total of 45 patients were included in this study. Twelve patients (26.7%) were treated in second-line and 33 patients (73.3%) were in third-line and later setting. Eighty percent and 15.5% patients had previously received pyrotinib/lapatinib and T-DM1, respectively. With a median follow-up of 24.4 months (range, 1.2 to 43.9 months), the median PFS was 7.6 months (95% confidence interval, 4.3 to 10.9), OS was not reached, the ORR was 31.1%, and DCR was 91.1%. The treatment was well tolerated. Conclusion The combination of trastuzumab biosimilar HLX02, pertuzumab, and chemotherapy exhibited promising efficacy and a favorable safety profile as second- and beyond-line treatment in HER2-positive MBC.