Abstract 2732: A self-replicating RNA precision medicine approach to therapeutic protein delivery of narrow therapeutic index biomolecules

Abstract

Abstract Protein drug replacement using nucleic acid technologies has been a sought-after solution for in situ production of proteins with poor half-lives and challenging manufacturability. Linear mRNA approaches have failed clinically in this technological use case due to low levels of protein expression and poor durability. Self-replicating RNA (srRNA) is a new technology for expression of biotherapeutics combining the advantages of fully synthetic drug products with higher peak levels of protein expression with active expression persisting out to 49 days. RBI-2000 is a novel srRNA encapsulated in a lipid nanoparticle and encoding two distinct proteins on the same strand of RNA. The first protein is a pro-inflammatory multimeric cytokine to promote de novo immune cell generation and infiltration. The second molecule is a single chain high affinity protein antagonist of downstream mediators of the inflammasome to prevent sterile inflammation, aberrant angiogenesis, and tumor invasiveness. We selected a novel alphaviral vector which demonstrated an enhanced peak level of protein expression vs. the prototypical vector that has been used in other RNA products. These encoded proteins elicited a pharmacodynamic response that had no evidence of decay in the first 7 days following a single treatment down to doses of 0.01 mcg. Using an implanted MC38 tumor model, tumor control was obtained at the lowest, single dose tested at 0.1 mcg of RBI-2000. When tested in combination with a checkpoint inhibitor (CPI), a single dose of the CPI and a single dose of RBI-2000 at 10 mcg resulted in 80% tumor control in the mice (8/10 mice). Tumor re-challenge of the mice at a site distal to the original implantation showed 100% protection. Collectively, these data demonstrate the feasibility of novel srRNA vectors as a protein drug replacement approach including for the expression of complex, multimeric cocktails of proteins. Citation Format: Zelanna Goldberg, Christian Maine, Gabrielle P. Dailey, Christine Domingo, Gaelle Picarda, Hunter Little, Annie Chou, Jessica Sparks, Darina Spasova, Shigeki Miyake-Stoner, Christopher A. Rabiola, Erika J. Crosby, Zachary C. Hartman, Herbert K. Lyerly, Nathaniel Wang, Parinaz Aliahmad. A self-replicating RNA precision medicine approach to therapeutic protein delivery of narrow therapeutic index biomolecules [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 2732.