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

Abstract EN

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-κB and interferon reporter cell lines to identify 4H-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 #1 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, #1 inhibited tubulin polymerization, and its effect on immune cell activation was abolished in cells mutated in the beta-tubulin gene (TUBB) encoding the site where colchicine binds.

Treatment with #1 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 #1 activated cytokine responses, we hypothesized that #1 could be effective for cancer immunotherapy.

Intratumoral injection of #1 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.