Real-world efficacy and safety of inetetamab-based therapy in HER2-positive metastatic breast cancer patients with prior exposure to trastuzumab

Yangyang Duan¹Tao Sun^1*Zhanhong Chen^2*Quchang Ouyang³Kai Li⁴Min Yan⁵Zheng Lv⁶Zhaohui Li⁷Li Man⁷Xu Luo⁷Yuyang Dong⁷Mingxi Jing¹Yan Wang¹Xiangyu Guo¹Junnan Xu¹Xiaorui Li¹Cui Jiang¹Ying E¹Lei Jiang¹Hui Cao¹Yufeng Jia¹Jie Wu¹Huan Li¹Liang Zhang¹Yujun Jiang¹Zhichao Gao¹Fangyuan Dong¹

• ¹Liaoning Cancer Hospital and Institute, Shenyang, China
• ²Zhejiang Cancer Hospital, University of Chinese Academy of Sciences, Hangzhou, China
• ³Hunan Cancer Hospital, Changsha, Anhui Province, China
• ⁴Shengjing Hospital of China Medical University, Shenyang, China
• ⁵The Affiliated Cancer Hospital of Zhengzhou University & Henan Cancer Hospital, Zhengzhou, China
• ⁶First Affiliated Hospital of Jilin University, Changchun, China
• ⁷Anshan Cancer Hospital, Anshan, China

Background: Until now there has been no comprehensive data from extensive samples to evaluate the therapeutic potential of inetetamab in metastatic breast cancer (MBC) patients who had a history of trastuzumab treatment. Some previous studies had either small sample sizes from single-center, or partial enrolled patients without prior exposure to trastuzumab. This study aimed to provide a deep analysis of inetetamab-based therapy in this specific population.A multicenter retrospective study collected clinicopathological data from a total of 500 patients between Jul 2020 and Oct 2023. Progression-free survival (PFS) was estimated as the primary endpoint. Secondary endpoints included objective response rate (ORR), disease control rate (DCR) and adverse events (AEs). The association of risk factors with the effect of inetetamab treatment on PFS was evaluated using Cox proportional hazards regression analysis.In the overall cohort, we observed a median PFS of 8.0 months, an ORR of 28.6% and a DCR of 89.2% (median treatment line: third line). Meanwhile, patients who received a combination treatment regime of inetetamab + tyrosine kinase inhibitors (TKIs) + chemotherapy achieved the most prolonged PFS of 9.0 months and the higher ORR of 29.3%. Ki67 index, distant lymph nodes metastasis and treatment strategy were independent predictors of PFS. The most common all-grade AEs were neutropenia (182/500, 36.4%) and leukopenia (157/500, 31.4%).Inetetamab was promising in HER2-positive MBC patients who had prior exposure to trastuzumab, offering a new option for patients with a prior failure of trastuzumab.