Induction Of Anti-Tumor Immunity By Intratumoral Delivery Of Mrna Encoding Cytokines And Tnfrsf Agonists.

Abstract In the recent decade several immune checkpoint inhibitors, such as anti-PD1/PD-L1 antibodies, have been approved by regulatory authorities and are actively used in oncology clinical practice. However, these antibodies exhibit durable anti-tumor benefits in only a small fraction of cancer patients. A major unmet medical need in immune oncology (IO) is extending the benefits of these therapies to patients who never experience tumor regression (primary resistance) and those who derive initial benefit before experiencing tumor progression (acquired resistance). Novel IO combinations have the potential to both sensitize primary resistant tumors and combat the acquisition of resistance to checkpoint inhibition. Synthetic, in vitro transcribed messenger RNA (mRNA) is an emerging therapeutic modality that offers the ability to express a broad range of therapeutic combinations. In this project, we proposed to ignite anti-tumor immunity locally through intratumoral (i.t.) delivery of a mixture of mRNAs encoding cytokines and a TNF receptor superfamily (TNFRSF) agonist. Using in vitro and in vivo screening, we identified a combination therapy consisting of three cytokines IFNα, IL-7, and a fusion protein of IL-15 with its receptor alpha chain as well as one TNFRSF agonist, an Fc fusion hexameric OX40L for enhanced receptor clustering. The mRNA mixture enhanced human antigen-specific T cell responses in vitro and displayed potent anti-tumor efficacy in syngeneic tumor models when injected i.t., demonstrating the induction of protective immunity. Importantly, in a preclinical dual-flank syngeneic tumor model, we demonstrated that this protective immunity extended beyond tumors injected with the lead mRNA mixture to control growth of distant untreated lesions. Mechanistically, the lead candidate induced anti-tumor immunity by recruiting dendritic cells to the tumor, leading to activation and expansion of tumor specific CD8 T cells. In summary, this mRNA mixture, encoding IFNα, IL-7, IL-15 and OX40L, induced potent anti-tumor immunity in mice and will be further investigated as a combination partner to overcome resistance mechanisms to immune checkpoint inhibition. Citation Format: Julie-Ann Gavigan, Chaomei Shi, Michael Lampa, Natalia Malkova, Qunyan Yu, Hui Qu, Mikhail Levit, Timothy Wagenaar, Christian Hotz, Xiangming Li. Induction of anti-tumor immunity by intratumoral delivery of mRNA encoding cytokines and TNFRSF agonists [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1711.