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/m²) 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.