Biomarker-Stratified Phase II Trial of Trastuzumab Rezetecan in Advanced Salivary Gland Carcinoma Across Cohorts With High and Low Human Epidermal Growth Factor Receptor 2 Expression
Guang-Liang Chen, Yanjing Guo, Xin Liu, Ya'nan Yang, Youzhou Sang, Xueguan Lu, Si Sun, Xiao Shi, Yan Zhang, Tong-Zhen Chen, Ning Qu, Duo Wen, Xiao-Shuang Niu, Shu Dong, Yu Wang, Yulong Wang, Jiachen Wang, Lu Zhang, Chaosu Hu, Qinghai Ji, Dongmei JiPURPOSE
Systemic treatment options for advanced salivary gland carcinoma (SGC) are limited, and prospective data for human epidermal growth factor receptor 2 (HER2)–directed therapy remain sparse, particularly in HER2-low disease. We evaluated trastuzumab rezetecan (SHR-A1811), a HER2-directed antibody-drug conjugate, in prospectively defined HER2-high and HER2-low cohorts.
PATIENTS AND METHODS
In this phase II trial, patients with unresectable locally advanced or recurrent/metastatic SGC were enrolled in separate HER2-high (immunohistochemistry [IHC] 3+ or IHC 2+/in situ hybridization [ISH]+) and HER2-low (IHC 1+ or IHC 2+/ISH–) cohorts. Each cohort was independently evaluated using Simon's optimal two-stage design. SHR-A1811 was administered intravenously once every 3 weeks at a recommended starting dose of 4.8 mg/kg. The primary end point was confirmed objective response rate (ORR) per RECIST version 1.1.
RESULTS
Forty-six patients were enrolled and treated, including 24 in the HER2-high cohort and 22 in the HER2-low cohort. The median follow-up was 21.9 months (95% CI, 16.9 to 26.9) and 11.3 months (95% CI, 6.9 to 15.7), respectively. The confirmed ORR was 91.7% (95% CI, 73.0 to 99.0), including four complete responses, in the HER2-high cohort and 45.5% (95% CI, 24.4 to 67.8) in the HER2-low cohort. Median progression-free survival (PFS) and overall survival (OS) were not reached in the HER2-high cohort. In the HER2-low cohort, the median PFS was 12.7 months and the median OS was 21.3 months. Grade 3 or higher treatment-related adverse events occurred in 41.3% of patients, most commonly neutrophil count decreased (32.6%). Interstitial lung disease occurred in 6.5% of patients, all grade 1. No treatment-related deaths occurred.
CONCLUSION
SHR-A1811 showed high antitumor activity in HER2-high SGC and promising activity in HER2-low SGC, with a manageable safety profile.