Efficacy, Safety, and Immunogenicity of HLX02 Compared with Reference Trastuzumab in Patients with Recurrent or Metastatic HER2-Positive Breast Cancer: A Randomized Phase III Equivalence Trial

BACKGROUND: HLX02 is an approved biosimilar of trastuzumab. OBJECTIVE: This study aimed to evaluated the efficacy, safety, and immunogenicity of HLX02 compared with reference trastuzumab in patients with human epidermal growth factor receptor 2 (HER2)-positive recurrent or metastatic breast cancer. PATIENTS AND METHODS: This randomized, double-blind, phase III study was conducted at 89 centers in China, the Philippines, Poland, and Ukraine. Eligible patients were randomized (1:1) to receive HLX02 or European Union (EU)-sourced trastuzumab (initial dose of 8 mg/kg, followed by 6 mg/kg every 3 weeks for up to 12 months) in combination with docetaxel intravenously. The primary endpoint was overall response rate up to week 24 (ORR(24)). Equivalence was declared if the 95% confidence interval (CI) of difference was within ± 13.5%. Safety and immunogenicity were evaluated in patients who received at least one dose of study medication. RESULTS: Between 11 November 2016 and 10 July 2019, a total of 649 patients were enrolled. The ORR(24) was 71.3 and 71.4% in the HLX02 (n = 324) and EU-trastuzumab (n = 325) groups, with a difference of − 0.1% (95% CI − 7 to 6.9), which fell entirely in the predefined equivalence margins. No statistically significant differences were observed in all secondary efficacy analyses. Safety profiles and immunogenicity were comparable in HLX02 and EU-trastuzumab groups. In total, 98.8% of patients in each group experienced at least one treatment-emergent adverse event (TEAE), 23.8 and 24.9% experienced serious TEAEs, and 0.6% in each group had antidrug antibodies. CONCLUSIONS: Among patients with HER2-positive recurrent or metastatic breast cancer, HLX02 demonstrated equivalent efficacy and similar safety and immunogenicity to reference trastuzumab. CLINICAL TRIAL REGISTRATION: Chinadrugtrials.org CTR20160526 (12 September 2016), ClinicalTrials.gov NCT03084237 (20 March 2017), EudraCT 2016-000206-10 (27 April 2017). SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40259-021-00475-w.