Abstract 5607: Broad acting glutamine antagonism remodels the tumor microenvironment, induces distinctive immune modulation, and synergizes with immune checkpoint blockade

Abstract

Abstract We previously reported that DRP-104, a novel broad acting glutamine antagonist, has significant therapeutic potential in cancer via directly targeting tumor metabolism and inducing a potent antitumor immune response. Here we sought to further elucidate the immunomodulatory effect of DRP-104 on tumor growth inhibition as a single agent and in combination with PD-1/PD-L1 checkpoint inhibitors in the MC38 and CT26 colon cancer syngeneic models. We utilized multiple technologies to assess mechanistic effects on immune cells in vivoincluding flowcytometry, multiplex immunoassay, gene expression profiling and GeoMx™ digital spatial profiling. DRP-104 mediated tumor growth inhibition was associated with increased tumor-infiltrating leukocytes (TIL) including T, NKT, and NK cells, M1-polarized tumor associated macrophages, and decreased immune-suppressive cells such as MDSCs. Nanostring® IO360 analysis revealed broad immunological modulation such as increase in cytotoxicity/antigen presentation score, increase in tumor metabolic stress/apoptotic score and decrease in cell proliferation score. GeoMx™ profiling also showed increased tumoral T cells and granzyme B expression. Luminex analysis of tumor lysates revealed DRP-104 treatment decreased pro-tumorigenic proteins, such as VEGF and IL-8. DRP-104 showed significant dose dependent tumor growth inhibition and regressions as a single agent in mouse syngeneic tumor models, including those resistant to immune checkpoint inhibitors. Lastly, combination of DRP-104 with anti-PD-1 Ab or anti-PD-L1 Ab further reduced tumor growth resulting in significant improvement in survival with long-term durable cures. In summary, DRP-104 treatment resulted in broad remodeling of the tumor microenvironment including enhanced infiltration and function of multiple immune cells distinct from activities obtained by a checkpoint inhibitor treatment. Combination therapy of DRP-104 with anti-PD-1/PD-L1 achieved significantly enhanced anti-tumor efficacy including long-term durable cures even in checkpoint inhibitor resistant models. This unique and non-overlapping mechanism of action supports clinical development of DRP-104 alone and in combination with PD-1/PD-L-1 checkpoint inhibitors. Citation Format: Yumi Yokoyama, Robert Wild. Broad acting glutamine antagonism remodels the tumor microenvironment, induces distinctive immune modulation, and synergizes with immune checkpoint blockade [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5607.