Abstract 3795: Crept-618: First GalNAc-siRNA targeting CREPT reverses HCC immune evasion and synergizes with anti-PD-1

Abstract Purpose: Immune checkpoint inhibitors (ICIs) achieve responses in only approximately ∼20% of hepatocellular carcinoma (HCC) patients due to immunologically “cold” tumors characterized by poor T-cell infiltration. We identify CREPT—overexpressed in HCC and linked to worse survival (HR=2.722, P=0.0018) and ICI non-response (higher expression in non-responders; GSE215011, P<0.01)—as a dual driver of tumor proliferation and immune silencing. We present CREPT-618, the first GalNAc-conjugated siRNA targeting CREPT. Experimental Procedures: CREPT expression was analyzed in TCGA, GEO, CPTAC databases and validated by immunohistochemistry in a 104-patient HCC tissue microarray. Functional roles were tested via CREPT knockdown in HCC cell lines (LM3, Huh7, Hep3B and Hepa1-6) using proliferation, migration, and invasion assays. In vivo efficacy was assessed in humanized orthotopic implantation mouse models with or without anti-PD-1 combination. The underlying mechanism was studied using RNA-seq, ATAC-seq, ChIP-seq, and scRNA-seq. CREPT-618 was tested for potency (no transfection), specificity, PK, biodistribution (Cy5/LC-MS), and GLP toxicology in mice, rats, and monkeys. New, Unpublished Data: CREPT recruits the SIN3A-HDAC1/2 complex to the CCL5 promoter, leading to chromatin compaction (ATAC-seq) and silencing IFN-γ/IRF1-induced CCL5 transcription (ChIP-seq). CREPT loss increased CCL5 secretion (3.7-fold, P<0.001), driving CD8+ T/NK infiltration (2.8-fold, P<0.01; scRNA-seq)—prevented by CCR5 blockade, confirming CCL5 dependence. CREPT-618 achieved potent, specific silencing (IC50 0.046-1.628 nM; RNA-seq/PCA validated) with liver-focused PK (Cmax ∼200 μg/g, T½ ∼70 h). In orthotopic HCC, monotherapy modestly suppressed growth across 3 batches (IHC target engagement confirmed), while combination with anti-PD-1 drove synergistic 78.3% tumor regression (P<0.001) and a 5.1-fold increase in cytotoxic CD8+ T cells. CREPT-618 was well-tolerated up to 100 mg/kg (rodents) and 30 mg/kg (monkeys). Conclusion: CREPT drives HCC growth and immune evasion by repressing CCL5, blocking T-cell recruitment via the CCL5-CCR5 axis. CREPT-618—the first siRNA targeting CREPT—silences this oncogenic hub, restores CCL5 signaling, converts “cold” tumors to “hot”, and synergizes with anti-PD-1. These preclinical data will enable a first-in-human trial; preliminary human safety and CREPT knockdown data will be presented at AACR. Citation Format: Jianghua Li, Alex Zou, He Yang, Jiayu Wang, Weihua Yang, Zhijie Chang, Jun Li. Crept-618: First GalNAc-siRNA targeting CREPT reverses HCC immune evasion and synergizes with anti-PD-1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 3795.