Abstract 1822: Novel DNA encoded tumor attacking bridges (dTABs) targeting IL13Rα2 display potent tumor control in an animal model of glioblastoma multiforme

Abstract Glioblastoma multiforme (GBM) is a highly aggressive brain tumor with poor clinical prognosis and there is significant need for new, improved therapies. Immunotherapy is a growing therapeutic research area for patients with advanced brain cancers. DNA encoded Tumor Attacking Bridges (dTABs) are bispecific antibodies that redirect T cell activity against Tumor Associated Antigens (TAAs) of interest. Here, we describe the design and development of in vivo generated dTABs targeting IL13Rα2, which is expressed in tumors of approximately 75% of GBM patients. Four dTABs targeting 2 different epitopes of IL13Rα2 were designed to compare alternate orientations of heavy and light chains in the dTABs. All dTABs bound to U87 cells expressing target as well as CD3 on T cells. The dTABs induced T cell activation, cytokine production, and tumor killing in the presence of target expressing tumor cells in a dose dependent manner. An important issue in the field of antibody guided therapies is on target - off tumor T cell activity which can cause serious side effects in patients. In order to minimize such toxicities, we identified one arrangement of dTAB which induced high T cell activation with potent tumor killing in the presence of target expressing tumor cells, but not when co-cultured with tumors that do not express IL13Rα2. We were able to detect expression of this lead dTAB for up to 19 days in the serum of NSG mice after a single DNA injection followed by electroporation. Serum from mice injected with this dTAB activated T cells which potently killed target expressing U87 GBM cells. In a subcutaneous xenograft mouse model of human GBM, this in vivo produced dTAB demonstrated significant tumor control and improved survival of mice. This study illustrates the potential of dTABs targeting IL13Rα2 as a novel approach for immunotherapy of this difficult to treat brain cancer. Citation Format: Pratik Sanjivkumar Bhojnagarwala, Ryan O'Connell, Daniel Park, Ebony Gary, Xizhou Zhu, David Weiner. Novel DNA encoded tumor attacking bridges (dTABs) targeting IL13Rα2 display potent tumor control in an animal model of glioblastoma multiforme [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1822.