Abstract B182: IGN004 is an antibody-interferon-alpha fusion protein against a novel tumor-associated antigen with both direct anti-tumor and immunostimulatory effects
Authors: Steward Kristopher , Gresser Michael , Sachdev Raj , Khare Sanjay 
Published: May 2016

Background: Antibody-IFNα fusion proteins represent a cancer therapeutic with properties of an antibody-drug conjugate and an immunotherapeutic agent, having both direct anti-tumor and immune-activating effects. These powerful molecules have the potential to target the anti-tumor cytotoxic effects of IFN to the tumor and to change the immunosuppressive tumor microenvironment to activate anti-tumor immunity. We previously reported the activity of IGN002, a recombinant anti-CD20-IFNα fusion protein, against human non-Hodgkin B-cell lymphomas (Yamada et al, JCO 2013). We now report the in vitro and in vivo anti-tumor activity of IGN004, an antibody-IFNα fusion protein against a novel tumor associated antigen expressed by many solid and liquid tumors.

Methods: IGN004 was evaluated against a panel of human non-small cell lung cancer (NSCLC), melanoma, multiple myeloma (MM), and acute myeloid leukemia (AML) cell lines. Antigen expression was assessed by flow cytometry and immunohistochemistry (IHC). Anti-proliferative activity was measured by MTS assay. MHC, costimulatory, and coinhibitory molecule expression was assessed by flow cytometry. T-cell killing of tumor cells by TALL-104 effector cells was assessed by MTS assay. Human tumor cell line and patient-derived xenografts were grown in immunodeficient mice.

Results: IGN004 antibody bound to the majority of tumor cell lines investigated, including melanoma, NSCLC, AML, and MM. In addition, IGN004 antibody also bound to nearly 100% of the primary solid tumor samples tested by IHC. IGN004 induced stronger growth inhibition than the unfused antibody and IFNα. Incubation of tumor cells with IGN004 caused an increase in surface expression of MHC class I, PD-L1, and OX-40L. In an in vitro T-cell killing assay using TALL-104 cells as effectors and NSCLC cells as targets, treatment of tumor cells with IGN004 led to increased effector cell killing of tumor targets (69.2% killing without IGN004 vs. 100% killing with IGN004; p = 0.001). The enhanced T-cell killing was observed even with concentrations at the sub-picomolar level (EC50 = 0.87 pM). Importantly, IGN004 demonstrated robust in vivo efficacy against MM, AML, melanoma, and NSCLC xenografts, including patient-derived tumors. Against U266 MM xenografts, IGN004 fusion protein caused complete regression of all established tumors and achieved long-term survival in 62.5% of mice. IGN004 unfused antibody caused a significant delay in tumor progression (p=0.002 vs. vehicle) but did not achieve long-term survival (p=0003 vs. IGN004 fusion protein). When efficacy was tested against a panel of patient-derived NSCLC xenografts, IGN004 fusion protein demonstrated efficacy against 7/11 tumor models, including tumor regression in 3. Against a patient-derived xenograft model of melanoma, IGN004 unfused antibody was ineffective while IGN004 fusion protein inhibited the growth of the tumors. In a patient-derived xenograft model of AML, IGN004 treatment caused a reduction in the percentage of AML cells in the blood, spleen and bone marrow, compared to PBS treated animals.

Conclusions: IGN004 demonstrated robust in vitro and in vivo anti-tumor activity against both solid and liquid tumors. Treatment of tumor cells with IGN004 caused an increase in surface expression of MHC class I, PD-L1, and OX-40L. IGN004 demonstrated the ability to enhance the effector T-cell-mediated killing of NSCLC cells in an in vitro assay using the TALL-104 cell line as effectors and NSCLC cell lines as targets. Against both cell line and patient-derived human xenograft tumors IGN004 had robust in vivo anti-tumor efficacy. These results support the further development of IGN004 as a potent targeted cancer immunotherapeutic agent that also has direct anti-tumor effects.

Citation Format: Kristopher Steward, Michael Gresser, Raj Sachdev, Sanjay Khare. IGN004 is an antibody-interferon-alpha fusion protein against a novel tumor-associated antigen with both direct anti-tumor and immunostimulatory effects. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr B182.