Abstract 4690: Hexavalent CD27 agonists show single agent anti-tumor activity and enhanced memory formation in mouse syngeneic tumor models

Tumor necrosis factor receptor superfamily (TNFRSF) proteins are widely expressed by immune and tumor cells highlighting their importance in multiple locations and phases of the anti-tumor immune response. Apogenix has developed a proprietary technology platform for the construction of novel hexavalent TNFRSF agonists (HERA) for the treatment of cancer. HERA fusion proteins comprise a perfect molecular mimic of the TNFSF cytokine structure and are based on dimerization of trivalent single-chain TNFSF receptor-binding domains (scTNFSF-RBD) via a Fc-γ receptor (FcγR) binding deficient immunoglobulin Fc domain. As a result of this molecular design, HERA proteins are capable of clustering six receptors in a spatially well-defined manner. Signaling following treatment with the Apogenix HERA “scTNFSF-RBD-Fc fusion proteins” is entirely independent of secondary crosslinking through FcγRs that is required for many agonistic anti-TNFRSF antibodies. The HERA engineering concept has been successfully translated to TRAIL, GITRL, CD40L, LIGHT and CD27L resulting in agonists that are currently in development. CD27L is a potent co-stimulatory molecule that drives T cell activation and survival through interaction with its receptor (CD27). HERA-CD27L is expressed in CHO suspension cells followed by a lab-scale purification process that results in homogenous aggregate-free protein lots. The purified protein binds its respective target-receptor with high affinity. In vitro, HERA-CD27L was able to bind CD27 expressed on primary human CD4+ and CD8+ T cells. Binding significantly increased T cell expansion following αCD3/αCD28 stimulation and leads to increased expression of OX40 on CD4+ T cells and 4-1BB on CD8+ T cells, respectively. In vivo, a single dose of 10mg/kg HERA-CD27L increases clonal expansion of antigen-specific CD8+ T cells upon immunization with Ovalbumin (Ova) in the mouse OT-1 model with a kinetics leading to peak levels of >25% Ova-specific CD8+ T cells at day 6 after treatment. Anti-tumor efficacy of HERA-CD27 was evaluated in MC38-CEA and CT26 colorectal syngeneic murine tumor models. In both models treatment with HERA-CD27L resulted in a dose dependent inhibition of tumor growth. CT26 tumor bearing mice treated with 1mg/kg HERA-CD27L, twice weekly showed an 85% tumor-growth inhibition (TGI) compared to the control group. A significant TGI of 48% could be observed in the MC38-CEA model upon treatment with 10mg/kg, twice weekly. Analysis of peripheral lymphoid tissues in the MC38-CEA bearing mice could furthermore show that HERA-CD27L treatment is accompanied with enhanced memory formation in both CD4+ & CD8+ T cells. In summary, the data on the hexavalent HERA-CD27L indicate a potent immune cell driven anti tumor efficacy. Therefore, HERA-CD27 agonists could be applied for the treatment of cancer as a single agent or in combination with check-point Inhibitors. Citation Format: Christian Gieffers, David Richards, Jaromir Sykora, Mauricio Redondo-Muller, Meinolf Thiemann, Christian Merz, Karl Heinonen Heinonen, Viola Marschall, Harald Fricke, Oliver Hill. Hexavalent CD27 agonists show single agent anti-tumor activity and enhanced memory formation in mouse syngeneic tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4690. doi:10.1158/1538-7445.AM2017-4690