Abstract 860: Experimental alpha-radioimmunotherapy for liver metastasis of gastric cancer

Abstract

Abstract Gastric cancer (GC) is one of the leading causes of cancer-related death worldwide. Early stage of GC is curable by surgical therapy or endoscopic surgery. However, previous studies reported that 35% of patients is present with evidence of distant metastasis at the time of diagnosis of GC. Metastatic GC is fetal and the patients with metastatic GC has extremely poor prognosis because current therapeutic approaches to metastatic GC are still limited. Therefore, the development of new therapeutic options has been eagerly awaited. Liver metastasis of GC (LMGC) is often observed during GC progression. It has been shown that 4-14% of the patients has LMGC. It is believed that LMGC is occurred by blood-borne metastasis of GC cells via blood stream. A previous study reported that approximately 70% of LMGC was positive for human epidermal growth factor receptor 2 (HER2). Therefore, HER2 may be a reliable therapeutic target for LMGC. Alpha-particle radioimmunotherapy (alpha-RIT) is an emerging new therapy, in which radioisotopes emitting cytotoxic alpha-particle radiation are delivered to target cancer cells to kill the cells by target-specific antibody. Among alpha-particle emitters, astatine-211 (At-211) is a promising emitter because it emits highly cytotoxic alpha-particles during its decay process with a half-life of 7.2 hours. The aim of this study is to evaluate the therapeutic efficacy and toxicity of At-211-labled anti-HER2 antibody trastuzumab ([At-211]trastuzumab) in a preclinical mouse model of HER2-positive LMGC. We established a mouse model of LMGC by injection of luciferase-labelled HER2-positive human metastatic GC cells (NCI-N87) into splenic vein of severe combined immunodeficiency mouse. Biodistribution studies revealed that the maximum tumor uptake of [At-211]trastuzumab was about 12% of injected dose per tissue gram 24 hours after injection. In experimental therapies, a systemic injection of [At-211]trastuzumab (1 MBq) significantly reduced a tumor burden in the liver and prolonged the survival. Transient but recoverable leukocytopenia was observed in mice received 1 MBq of [At-211]trastuzumab at 5-7 days after injection. No body weight loss was found during the observation period. In this study, we provides a preclinical evidence that alpha-RIT using [At-211]trastuzumab may be a new therapeutic option against LMGC. Citation Format: Huizi Keiko Li, Sumitaka Hasegawa. Experimental alpha-radioimmunotherapy for liver metastasis of gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 860.