Abstract 4573: STINGVAX - A novel tumor vaccine with cyclic dinucleotides - can induce potent anti-tumor responses in vivo.

Abstract

Abstract Cyclic dinucleotides (CDN) are ubiquitous bacterial intracellular messengers, and they have recently been shown to also function as a pathogen associated molecular pattern (PAMP) molecules that are sensed by eukaryotic host Stimulator of Interferon Genes (STING) that can activate the TBK-1/IRF-3 signaling pathway to induce type I interferon and other co-regulated genes. CDN was found to induce STING dependent augmentation of T-cell priming in multiple vaccination models, potentially by activating dendritic cells. We formulated CDN with a GM-CSF secreting tumor cell vaccine (STINGVAX) to mobilize and as well as activate dendritic cells both in vitro and in vivo. STINGVAX was tested in a stringent B16 melanoma treatment model, and we demonstrated significant reduction of tumor growth rate in vivo. STINGVAX's anti-tumor response was correlated with increased tumor infiltrating CD8 T-cells as well as increased number of p15E tumor-specific cytotoxic T-cells. STINGVAX's in vivo anti-tumor response was T-cell dependent as well as STING dependent. When we combined STINGVAX with multiple TLR 4/7/8 agonists signaling through the MyD88/TRIF pathway that is distinct from CDN/STING/TBK-1 signaling treatment of palpable B16 tumor resulted in regression of 30-60% of these non-immunogenic tumors. When the STINGVAX treated tumor microenvironment was examined, both IFNγ+CD8+ and PD-L1 was upregulated, potentially demonstrating an adaptive immune resistance mechanism which would render STINGVAX an excellent candidate to be combined with anti-PD-1 blockade. Cumulatively, STINGVAX is a novel tumor vaccine with a high potential for translation in clinical oncology. Citation Format: Thomas W. Dubensky, Meredith L. Leong, David B. Kanne, Edward E. Lemmens, Ken Metchette, Weiqun Liu, Marcella Fasso, Juan Fu, Joshua J. Woodward, Drew Pardoll, Daniel A. Portnoy, Young J. Kim. STINGVAX - A novel tumor vaccine with cyclic dinucleotides - can induce potent anti-tumor responses in vivo. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4573. doi:10.1158/1538-7445.AM2013-4573