A multi-targeted T-cell engagement of PD1-resistant colorectal cancer cells via delivery of glycopeptide conjugates.

e14571 Background: Glycan-based cancer immunotherapies are novel therapeutic strategies that use the pivotal role of aberrant glycosylation patterns in cancer progression. Targeting hybrid epitopes consisting of altered glycans and carrier peptides enhances the efficacy and specificity of the anti-tumor immune response. Here, we exploit ensembles of glycopeptide conjugates to steer a multi-targeted yet tumor-specific T-cell response, a technology we call GLAAD (glycopeptides with adjuvant and tumor-associated antigen delivery). By inducing T cells that recognize and eliminate tumor cells and promoting their antigenicity in a therapeutic setting, we show the potential of our GLAAD candidate GNU-101 to overcome the transient and heterogeneous responses frequently observed with traditional immunotherapies. Methods: Using the MC38 syngeneic mouse model of colorectal cancer (CRC) in a therapeutic setting, we tested whether GNU-101 reduces tumor burden when orally administered alone or combined with immune checkpoint inhibitors (ICI). On day 0, 20 C57/BL6J mice were injected subcutaneously with MC38 CRC cells in each flank. On day 6, mice were supplemented with 3% GNU-101 in the drinking water, while control mice received normal drinking water. On days 6, 9, 12, and 15, half of the mice in each group received an anti-PD1 antibody (aPD1), while the others received isotype control. On day 16, the mice were sacrificed. Results: In this therapeutic setting, a standalone therapy of GNU-101 successfully reduced tumor growth as demonstrated by a statistically significant reduction in both tumor volume and weight. As expected, the aPD1 therapy had only a non-significant effect on tumor growth. Remarkably, its efficacy was improved when combined with GNU-101, leading to a statistically significant reduction of >90% in tumor volume and weight. The analysis of the immune cell population in the tumor microenvironment revealed the activation of CD8 T cells and a reduction of immunosuppressive signals, which likely mediates the anti-tumor efficacy of GNU-101. This was obvious by a higher abundance of CD8 T cells producing IFNγ and secreting granzyme B & perforin and, conversely, lower amounts of Tim3+ CD8 T cells and regulatory T cells (FoxP3+ CD4 T cells) found in mice treated with GNU-101 vs control mice. Conclusions: We demonstrate the immunomodulatory and therapeutic potential of GNU-101 in a pre-clinical mouse study in which the growth of established tumors was significantly reduced, either as a standalone therapy or in combination with existing treatment. By specifically promoting anti-cancer CD8+ T cells while reducing immunosuppressive signals, this easy-to-administer glycopeptide has the potential to create the conditions for long-term cancer control and improve treatment outcomes in cancer that are frequently resistant to immunotherapy, such as many epithelial cancers.