Background: RXC004, a potent and selective inhibitor of the Wnt/β-Catenin pathway regulator porcupine, is being investigated in a safety and tolerability study in cancer patients with solid tumors (NCT03447470). We present pre-clinical data confirming the potential for RXC004 in modulating the immune system of the tumor microenvironment.

Materials and Methods: To evaluate RXC004 as an immunomodulatory anti-cancer agent we took two complementary approaches; first utilizing a syngeneic B16F10 melanoma model in C57BL/6 mice. A range of doses and schedules of RXC004 were tested for 28 days and efficacy was measured by tumor volume. To further probe the mechanism of immune modulation by RXC004 in syngeneic models, global gene expression in the tumor microenvironment (TME) was analyzed using the Nanostring IO 360 gene set, and immune cell populations in the blood and spleen were analyzed by flow cytometry. In the second approach, modulation of a range of immune-relevant biomarkers by RXC004 was assessed in a panel of Wnt ligand-dependent human cancer cell lines using flow cytometry and gene expression.

Results: In the syngeneic B16F10 melanoma model, RXC004 treatment significantly reduced tumor volume in a dose-dependent manner at 0.5, 1.5 and 5 mg/kg QD. In addition, 5mg/kg QD of RXC004 scheduled 5 days on, 2 days off also gave significant efficacy. RXC004 treatment in this model is known to decrease myeloid-derived-suppressor-cells (MDSCs) within the TME. Consistent with this, RXC004 treatment (5mg/kg QD) increased the proportion of MDSCs circulating in blood. MDSCs are therefore either retained in the TME through Wnt pathway signaling, or Wnt pathway signaling promotes chemotaxis of these cells to the TME. Analysis of a panel of immune genes using Nanostring IO 360 demonstrated RXC004 treatment (5mg/kg QD) increased expression of chemokine and cytokine signaling components in the TME, such as the T cell chemoattractant CXCL9. CXCL9 is reported to be produced by CD103+ve dendritic cells in the mouse TME and absence of these dendritic cells is linked to a lack of T cell infiltrate (Spranger et al., 2017). In a panel of Wnt ligand-dependent human cancer cells, RXC004 treatment regulated levels of markers associated with tumors evading the immune system e.g. MYC expression levels were reduced significantly. Modulation of such markers in paired clinical sample may indicate an immune-modulatory response to RXC004.

Conclusion: Taken together, Wnt pathway suppression by RXC004 treatment can enhance the immune response against tumors by 1) directly regulating levels of immune-relevant markers on cancer cells, and 2) enhancing the immunity of the TME by decreasing MDSCs and increasing chemokine and cytokine signaling.

Spranger et al Cancer Cell 2017 8 31(5):711-723

Citation Format: Caroline Phillips, Inder Bhamra, Catherine Eagle, Alicia Edmenson Cook, Cliff Jones, Simon Woodcock. Wnt/â-Catenin pathway inhibitor RXC004 enhances the immunity of pre-clinical models of cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 506.