Abstract 4239: Development of multi-targeting immunomodulatory SeekR RNA therapeutics to overcome resistance to PD-1 blockade

Abstract

Abstract T-cell exhaustion describes the dysfunctional state of effector T cells in the tumor microenvironment that results from chronic and prolonged exposure to antigen. It also represents an important mechanism of clinical resistance to immune checkpoint blockade. Recently, the transcription factor NR4A1 has been shown to be upregulated in tumor-specific T cells and plays a role in driving exhaustion during chronic antigen stimulation of T cells. Pro-oncogenic activities of NR4A1 have long been observed in various solid tumors including colorectal and breast cancers, and co-expression of NR4A1 with known immune checkpoint markers such as PD-L1 have also been observed in various cancer cell lines. These findings have identified NR4A1 as an important target for overcoming resistance to cancer immunotherapy. We hypothesize that multi-targeting to simultaneously block PD-1 signaling and silence NR4A1 gene expression can reverse T-cell exhaustion and expand the clinical benefit of PD-1 blockade in immune therapy resistant solid tumors. Using our SeekR™ RNA therapeutics platform, we combined aptamer binders to PD-1 with siRNA against NR4A1, andNR4A1 and evaluated their ability to reverse T-cell exhaustion and re-activate T-cell based anticancer immunity in solid tumors. Specifically, we created SeekR™ therapeutic RNA molecules with dual flanking RNA aptamers binders to PD-1 and other checkpoint inhibitors, connected by a double stranded bridge that encodes for siRNA silencers that target multiple immunomodulatory genes, such as NR4A1. The novel anti-PD-1 RNA aptamer component serve to: A) direct and deliver the SeekR™ RNA oligo therapeutics to exhausted T-cells that express PD-1 receptors; and B) internalize the siRNA component into the T-cells. The siRNA components of the SeekR™ serve to silence NR4A1 which lead to reversal of the cytotoxic T-cell exhausted phenotype following chronic in-vitro stimulation. These results demonstrate that dual targeting of PD-1 and NR4A1 has the potential to reverse T-cell exhaustion and the potential to overcome cancer immunotherapy resistance in the clinic. Citation Format: Marvin O'ketch, Victoria A. Love, Jeffrey A. Kiefer, David W. Lee, Lizette A. Castaño, Spyro Mousses, David O. Azorsa. Development of multi-targeting immunomodulatory SeekR RNA therapeutics to overcome resistance to PD-1 blockade [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 4239.