Activation Of Innate And Adaptive Immunity Via Combinatorial Immunotherapy Using Synthetic Biotic (Tm) Medicines

Background: While both T-cell priming and blockade of immune suppression play critical roles in the generation of an efficacious antitumor immune response, most therapies fail to support both processes as a single agent. At Synlogic we are using synthetic biology and engineered bacteria programmed with immune-modulatory circuits to develop treatments or “Synthetic Biotic Medicines” capable of simultaneously manipulating multiple pathways relevant for the treatment of cancer and autoimmunity. Recent studies have demonstrated that activation of the st imulator of in terferon g enes (STING) pathway can play a critical role in the initiation of an antitumor immune response via activation of antigen presenting cells (APCs) and presentation of tumor antigens. Additionally, metabolites derived from biosynthetic pathways, such as conversion of tryptophan into kynurenine by i ndoleamine 2,3 d i o xygenase (IDO), have also been recently appreciated as major components of the immune-suppressive tumor microenvironment which lead to T cell disfunction and exhaustion. Here we present results showing the development of two circuits, an immune “initiator” STING activating circuit (SYN-STING) and an immune “sustainer” Kynurenine consuming circuit (SYN-Kyn), in engineered strains of E. coli Nissle. Methods and Results: Synthetic biological techniques were employed to generate bacterial strains expressing various protein components capable of (1) generating the STING agonist cyclic-di-AMP (SYN-STING) or (2) actively transporting and metabolizing kynurenine (SYN-Kyn). In in vitro biochemical and functional assays, SYN-STING generated high levels of cyclic-di-AMP and triggered the expression of IFNβ1 and IL-6 upon co-culture with APCs, while SYN-Kyn actively depleted test media containing kynurenine at levels 20-fold higher than those found in tumors of cancer patients. In mice bearing subcutaneous syngeneic tumors the intratumoral administration of SYN-STING resulted in an early rise of innate cytokines which several days later shifted towards molecules indicative of an effector-T-cell response. Additionally the administration of a single dose of SYN-Kyn led to significant decreases in tumor kynurenine levels for up to 72 hours post dose. Finally, administration of a combination of either SYN-STING with anti-PD1 or SYN-Kyn with anti-CTLA4 antibodies in tumor-bearing mice led to significant anti-tumor effects over those observed for the antibodies alone. Conclusions: Taken together, these results demonstrate that the use of synthetic biology to engineer bacteria is a viable approach to deliver profound efficacy in experimental models of cancer. The data supports the further development of Synthetic Biotic Medicines capable of locally targeting multiple immune pathways as single immuno-oncology therapeutic agents. Citation Format: Daniel Leventhal, Kip West, Adam Fisher, Anna Sokolovska, Starsha Kolodziej, Ning Li, Chris Plescia, Carey Gallant, Mary Castillo, Paul Miller, Jose Lora. Activation of innate and adaptive immunity via combinatorial immunotherapy using Synthetic Biotic ™ Medicines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-131.