22MO - Efficacy and safety of sacituzumab govitecan in Chinese patients with metastatic triple-negative breast cancer (mTNBC) by baseline HER2 expression level: Subgroup analysis from a phase IIb trial

Background

About 30-40% of mTNBC patients (pts) have tumors with HER2 low expression, which might be a potential target of some novel anti-HER2 agents. Sacituzumab govitecan (SG), a novel Trop2-targeted antibody-drug conjugate, has been approved for second line onwards mTNBC treatment by Singapore and NMPA recently. To better understand the role of SG in the treatment of Chinese mTNBC with different HER2 expression level, subgroup data of EVER-132-001 were analyzed.

Methods

EVER-132-001 is a multicenter, single-arm, Phase IIb study of SG in Chinese pts with mTNBC who received at least two prior systemic treatments. In this subgroup analysis, HER2 status of the most recent tumor biopsy tissue was evaluated by immunohistochemistry [IHC] and Fluorescence in situ hybridization [FISH] locally. Pts were divided into 2 subgroups: HER2-neg (IHC 0) and HER2-low (IHC 1+, or IHC 2+ and FISH negative). Efficacy and safety of SG across subgroups were analyzed and reported.

Results

Of the 80 mTNBC pts enrolled, there were 43 reported HER2-neg and 37 HER2-low (IHC 1+, n=20). Demographics, baseline disease characteristics and prior anticancer treatments were generally balanced across the two subgroups. The median number of prior systemic therapies was 4 in both subgroups. According to Independent Review Committee assessment, objective response rate was 41.9% (95% confidence interval [CI] 27.01-57.87) in HER2-neg group and 35.1% (95% CI 20.21-52.54) in HER2-low group, and clinical benefit rate was 46.5% (95% CI 31.18-62.35) and 40.5% (95% CI 24.75-57.90), respectively. Median progression free survival was 6.9 months (95% CI 4.21-NA) in HER2-neg and 5.5 months (95% CI 2.83-NA) in HER2-low. SG-related CTCAE Grade ≥3 treatment-emergent adverse events reported were similar (69.8% vs 73.0%), and the most common ones both were neutrophil count decreased (62.8% vs 62.2%), white blood cell count decreased (44.2% vs 54.1%), and anemia (23.3% vs 18.9%).

Conclusions

SG showed comparable anti-tumor activity in both HER2-neg and HER2-low subgroups of later line Chinese mTNBC pts. The safety profile was consistent across two subgroups and both manageable.

Clinical trial identification

NCT04454437, First posted: July 1, 2020.

Editorial acknowledgement

Legal entity responsible for the study

Everest Medicines.

Funding

Everest Medicines.

Disclosure

X.J. Cong, N. Wang, C. Xu, J.J. Chen: Financial Interests, Personal, Other, employee: Everest Medicines. All other authors have declared no conflicts of interest.