429 Eribulin Synergizes with STING Agonists by Enhancing Type 1 Interferon Expression and Improves Antitumor Efficacy as Combination Treatment

OBJECTIVES/GOALS: Triple-negative breast cancer (TNBC) is a subtype of breast cancer that lacks effective targeted treatment options. TNBC's greater degree of immunogenicity than other breast tumors makes immunotherapy a viable strategy. Strategies to improve the immunotherapy response includes targeting the cGAS-STING innate immune pathway with STING agonists. METHODS/STUDY POPULATION: We have previously shown in vitro that eribulin, a microtubule destabilizer currently used in the treatment of TNBC, functions as an indirect STING agonist because it promotes the release of mitochondrial DNA into the cytoplasm. Separately, eribulin also significantly enhances type I interferon expression induced by STING agonists measured by qRT-PCR through a second TBK1-dependent mechanism downstream of STING activation through detecting higher amounts of phosphorylated IRF-3 by western blot protein analysis. Mechanisms of eribulin-mediated interferon expression occur in immune and TNBC cells and are shared with other microtubule destabilizers but not with the microtubule stabilizing agent paclitaxel. RESULTS/ANTICIPATED RESULTS: We determine that the enhancement of type I interferon expression by eribulin is pharmacologically synergistic with multiple STING agonists. The significant enhancement by eribulin led us to evaluate the antitumor efficacy of eribulin in combination the STING agonist ADU-S100 in a challenging spontaneous mammary tumor model MMTV-PyVT. We show that the combination treatment significantly decreased tumor growth which allowed for longer survival compared to other groups. This is particularly interesting because of our previous studies showing that eribulin alone, but not paclitaxel, promotes the activation of CD4+ T-cells in the spleen and draining lymph nodes of BALB/c mice with 4T1 tumors through flow cytometric analysis. DISCUSSION/SIGNIFICANCE: These data contribute to accumulating evidence that there are important mechanistic differences between the microtubule targeted chemotherapeutics currently used in the treatment of TNBC and suggest that eribulin can act as an immune adjuvant in addition to its anti-mitotic effect.