Abstract 5165: In vivo therapeutic validation of NRT-YHD_001, a novel macrophage checkpoint inhibitor, in liver cancer

Abstract Previously, we demonstrated that recovery of Histone deacetylase 6 (HDAC6) elicited let-7i-5p suppression to de-repress the thrombospondin-1 (TSP1) expression, and thereby it occupied CD47 receptor to block CD47-SIRPα mediated anti-phagocytosis of macrophage in liver cancer. NRT-YHD_001 is a modified antisense miRNA of let-7i-5p for liver cancer treatment. NRT-YHD_001 was substituted with O-methoxyethyl and phosphothioate for stability, and N-acetylgalactosamine was attached for specific delivery to the liver. In in vitro phagocytosis assay, NRT-YHD_001 showed macrophage phagocytosis activity with similar or better results compared to non-modified antisense let-7i-5p (AS_let-7i-5p). In addition, it was confirmed that NRT-YHD_001 inhibited endogenous let-7i-5p of liver cancer cells and activated macrophage phagocytosis at 4°C or 25°C for up to 2 weeks. When NRT-YHD_001 activity was investigated in vivo after 1 week, 2 weeks, and 4 weeks after administration of single dose NRT-YHD_001 to the tail vein of a mouse, NRT-YHD_001 was not degraded, and let-7i-5p was inhibited while maintaining activity in liver tissue for 2 weeks after injection. To investigate the in vivo therapeutic effect, a mouse spontaneous (Ras-transgenic) liver cancer model was used and compared with the sorafenib-administered group. After administration of NRT-YHD_001 and sorafenib each week at the time when liver mass was detected, the tumor size and growth rate were compared. As a result, the NRT-YHD_001 administration group showed significant therapeutic effect compared to sorafenib. These results showed that NRT-YHD_001 had a strong anticancer effect by converting the macrophage of don't eat me into eat me signal in the tumor microenvironment of liver cancer, thereby removing or inhibiting liver cancer cells. Keywords: let-7i-5p, macrophage, phagocytosis, liver cancer, NRT-YHD_001 Citation Format: Suk Woo Nam, Sangyean Kim, Min Jeong Na, Eunbi Shin, Jin Woong Ha, Soyoung Jeon, Jeong Hwan Yoon. In vivo therapeutic validation of NRT-YHD_001, a novel macrophage checkpoint inhibitor, in liver cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5165.