Abstract NRT-YHD_001, a modified antisense miRNA targeting let-7i-5p for liver cancer therapy, acts as a key regulator of macrophage activity within the tumor microenvironment. Through in vitro pharmacology studies, we identified anticancer effects not only on cell growth, proliferation, viability, migration, and invasion but also through the enhancement of macrophage phagocytosis. To evaluate the in vivo efficacy of NRT-YHD_001, we used a Ras-transgenic mouse liver cancer model which develops spontaneous liver cancer mass after 15 ∼ 20 weeks of birth. Based on dose-dependent and injection interval studies, the optimal regimen was determined to be 1 mg/kg administered weekly. We confirmed that weekly intravenous injections of 1mg/kg NRT-YHD_001 showed significantly greater therapeutic efficacy than the sorafenib-treated group. Additionally, xenograft assay using human liver cancer cells in athymic-nude mice showed that weekly injection of NRT-YHD_001 led to improved survival and tumor growth inhibition compared to the untreated group. We performed Absorption, Metabolism, Distribution, and Excretion studies for NRT-YHD_001, stability studies in serum and liver homogenate, and metabolite identification and profiling analysis were completed in mice and cynomolgus monkeys. In maximum tolerated dose (MTD) studies conducted in mice and cynomolgus monkeys, no toxicity of NRT-YHD_001 was observed at doses up to 500 mg/kg administered intravenously. Furthermore, comprehensive evaluations across 4-week repeated dose toxicity and toxicokinetic in mice and monkey, safety pharmacology, and genetic toxicity studies revealed no adverse findings with NRT-YHD_001. For NRT-YHD_001, Drug Substance (DS) and Drug Product (DP) were produced by a global CDMO with experience in U.S. FDA approval of oligonucleotide drugs, and the analysis method was established.These results enabled us to complete the IND-enabling study package for NRT-YHD_001, a liver cancer therapy candidate with FTO analysis completed and intellectual property (IP) fully secured. Regulatory approval submissions to the Korea MFDS and the U.S. FDA are planned for 2025. Citation Format: Suk Woo Nam, Jin Woong Ha, Sang Yean Kim, Min Jeong Na, Soyoung Jeon, Bee Yoo, In Seop Yoon, Hyunmin Lee, Chang Won Park. IND enabling study of NRT-YHD_001, a macrophage immune checkpoint inhibitor in liver cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3209.