Abstract PR-01: Systemic targeting of therapeutic RNA to pancreatic ductal adenocarcinoma via a novel, cell-penetrating, and nucleic acid-binding monoclonal antibody

Abstract There is intense interest in developing nucleic acid ligands for immune stimulation of the tumor microenvironment via pattern recognition receptors (PRRs), particularly for treating “cold” tumors like pancreatic ductal adenocarcinoma (PDAC). However, selective delivery of intact and functional RNAs after intravenous administration in a tumor-specific manner to avoid systemic toxicity has been challenging. Many current efforts rely on the direct intra-tumoral injection of RNAs or other stimulatory immune ligands, which is therapeutically sub-optimal, especially for pancreatic tumors and metastases. Here, we present a groundbreaking and unique cancer treatment approach using a lupus-derived, cell-penetrating antibody to deliver nucleic acids to PDAC tumors in vivo. This antibody, a modified version of the initially reported 3E10-D31N, designated TMAB3, forms non-covalent complexes with RNAs. We tested our delivery platform in genetically engineered mouse models (Pdx-1 Cre KrasG12D) and flank and orthoptic allographs of pancreatic cancer (Pdx-1 Cre KrasG12D, p53R172H/- KPC cells) in immunocompetent models. Using 3p-hpRNA, an agonist of the pattern recognition receptor retinoic acid-inducible gene-I (RIG-I), we observed robust anti-tumor efficacy of systemically administered TMAB3/3p-hpRNA complexes in an orthotopic pancreatic cancer model. Treatment tripled animal survival and decreased tumor growth, specifically targeting the malignant cells, with a 1500-fold difference in RNA delivery into tumor cells versus non-malignant cells within the tumor mass. While an immunosuppressive microenvironment typically characterizes PDAC, we found that RIG-I stimulation via TMAB3/3p-hpRNA treatment elicited a potent anti-tumoral immune response characterized by induction of apoptosis in tumor cells and infiltration of CD8+ T cells using single-cell RNASeq and confirming using FACS and immunocompromised mice. In vitro and in vivo studies demonstrated that cancer-cell delivery was mediated by nucleoside transporter ENT2, which is highly expressed in PDAC compared to healthy and benign tissues. These results were recapitulated in orthogonal models of immunologically cold tumors, including melanoma and medulloblastoma. Together, these studies demonstrate that the TMAB3 antibody can 1) precisely localize and enter pancreatic tumor cells, 2) promote CD8+ T cell infiltrates, and 3) rapidly deliver RNA payloads specifically to tumors. Given the known stromal barrier in pancreatic ductal adenocarcinoma, TMAB3 provides a novel targeted delivery platform for a broad range of therapeutics for these difficult-to-treat tumors. Citation Format: Diana Martinez-Saucedo, Elias Quijano, Zaira Ianniello, Madison Rackear, Yanfeng Liu, Denise Hegan, Haoting Chen, Xinning Shan, Robert Tseng, Deanne Yugawa, Natasha Pinto-Medici, Sumedha Chowdhury, Ranjit S Bindra, Marie E Robert, W. Mark Saltzman, Luisa F Escobar-Hoyos, Peter M Glazer. Systemic targeting of therapeutic RNA to pancreatic ductal adenocarcinoma via a novel, cell-penetrating, and nucleic acid-binding monoclonal antibody abstract. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84 (17 Suppl₂): Abstract nr PR-01.