Efficacy and safety of KN026 and docetaxel for HER2‐positive breast cancer: a phase II clinical trial

Abstract Background The standard first‐line treatment for human epidermal growth factor receptor 2 (HER2)‐positive recurrent/metastatic breast cancer currently includes pertuzumab plus trastuzumab and docetaxel. This study aimed to evaluate the effectiveness of KN026, an anti‐HER2 bispecific antibody, plus docetaxel in first‐line treatment of HER2‐positive recurrent/metastatic breast cancer. Methods This open‐label, single‐arm, phase II study enrolled patients with HER2‐positive recurrent/metastatic breast cancer in 19 centers across China from December 30, 2019 to May 27, 2021. Patients were administered KN026 (30 mg/kg) plus docetaxel (75 mg/m 2 ) in 21‐day cycles. Primary endpoints included the objective response rate (ORR) and duration of response (DOR). In addition, overall survival (OS), progression‐free survival (PFS), clinical benefit rate (CBR) and safety profile were examined. Results A total of 57 patients were included. In the efficacy analysis set of 55 patients, the ORR was 76.4% (95% confidence interval [CI], 63.0%‐86.8%), and the CBR was 85.5% (95% CI, 73.3%‐93.5%). The median DOR was not reached (95% CI, 20.7 months‐not reached). In the safety set of 57 patients, the median PFS was 27.7 months (95% CI, 18.0 months‐not reached). The median OS was not reached, with OS rates at 12, 24 and 30 months of 93.0%, 84.1% and 78.5%, respectively. Grade ≥3 treatment‐emergent adverse events (AEs) were detected in 36 (63.2%) patients. No deaths were attributed to KN026 or docetaxel. Conclusion KN026 plus docetaxel showed promising efficacy and a manageable safety profile in first‐line treatment of HER2‐positive recurrent/metastatic breast cancer.