Discovery of a Novel Microtubule Targeting Agent as an Adjuvant for Cancer Immunotherapy.

For an activating immunotherapy such as adjuvants, a compound that can prolong immune stimulation may enhance efficacy. We leveraged data from two prior high throughput screens with NF-B and interferon reporter cell lines to identify 4-chromene-3-carbonitriles as a class of compounds that prolonged activation in both screens. We repurchased 23 of the most promising candidates. Out of these compounds we found to be the most effective agent in stimulating the release of cytokines and chemokines from immune cells, including murine primary bone marrow derived dendritic cells. Mechanistically, inhibited tubulin polymerization, and its effect on immune cell activation was abolished in cells mutated in the beta-tubulin gene () encoding the site where colchicine binds. Treatment with resulted in mitochondrial depolarization followed by mitogen-activated protein kinase activation. Because tubulin polymerization modulating agents have been used for chemotherapy to treat malignancy and activated cytokine responses, we hypothesized that could be effective for cancer immunotherapy. Intratumoral injection of delayed tumor growth in a murine syngeneic model of head and neck cancer. When combined with PD-1 blockade, tumor growth slowed in the injected tumor nodule and there was an abscopal effect in an uninjected nodule on the contralateral flank, suggesting central antitumor immune activation. Thus, we identified a new class of tubulin depolymerizing agent that acts as both an innate and an adaptive immune activating agent and that limits solid tumor growth when used concurrently with a checkpoint inhibitor.