Abstract 663: Systemic targeting of therapeutic RNA to cancer via a novel, cell-penetrating and nucleic acid binding, monoclonal antibody

Abstract There is intense interest in the development of nucleic acid ligands for immune stimulation of the tumor microenvironment via pattern recognition receptors (PRRs), particularly for the treatment of “cold” tumors. However, delivery of these ligands in a tumor-specific manner to avoid systemic toxicity has been a challenge. Many current efforts rely on direct intra-tumoral injection of RNAs or other stimulatory immune ligands, which is therapeutically sub-optimal, especially for metastatic disease. Here we report studies evaluating the utility of a lupus-derived, cell-penetrating antibody, to deliver nucleic acids to tumors in vivo. This antibody, a modified version of 3E10-D31N, designated GMAB, forms non-covalent complexes with RNAs and can mediate highly specific delivery into tumors via intravenous injection by targeting the nucleoside transporter ENT2, which is highly expressed in tumor cells. Studies with labeled RNAs showed tumor specific delivery and functional expression by imaging, with minimal delivery to healthy tissues. Following these proof-of-concept studies, we investigated whether our antibody could be used to deliver RIG-I agonists to tumors. Using a known agonist of RIG-I, 3p-hpRNA, we demonstrated single agent activity of our GMAB/RNA complexes in multiple tumor models, including a mouse model of melanoma (B16) and an orthotopic model of pancreatic cancer (KPC). Measuring 3p-hpRNA by RT-PCR, there was a 1000X fold difference in RNA uptake in KPC tumor cells relative to CD45+ cells isolated from tumors. In addition, synergy between our GMAB/RNA complexes and anti-PD-1 was additionally observed in mouse models of breast (EMT6) and colon (MC38) cancer. Given the expression of ENT2 along the blood brain barrier (BBB), we demonstrate single agent activity of our GMAB/RNA complexes in an orthotopic mouse model of medulloblastoma, resulting in suppression of tumor growth and spinal metastases. Together, these studies demonstrate that the GMAB antibody can 1) localize to orthotopic and flank tumor models, 2) cross the BBB, and 3) deliver RNA payloads to tumors, providing a novel platform for delivery of immunogenic RNAs, as well as mRNAs and siRNAs, directly to tumors with high specificity following systemic administration. Citation Format: Elias Quijano, Diana Martinez Saucedo, Minsoo Khang, Yanfeng Liu, Dale Ludwig, Bruce C. Turner, Stephen Squinto, Ranjit Bindra, W. Mark Saltzman, Luisa Escobar-Hoyos, Peter M. Glazer. Systemic targeting of therapeutic RNA to cancer via a novel, cell-penetrating and nucleic acid binding, monoclonal antibody [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 663.