Abstract 1823: Directing T cells using multivalent, bispecific chemically self-assembling nanorings (CSANs) to target brain tumors overexpressing EGFR and B7H3 antigens
Authors: Mews Ellie , Jackson Pauline , Kilic Ozgun , Delgado Justine , Patchava Mahathi , Largaespada David , Wagner Carston R. 
Published: July 2021

Abstract
Introduction: CNS solid tumors have few therapeutic options and disease progression is rapid especially in pediatrics. Current standard-of-care strategies with radiation and surgery typically result in severe neuroendocrine and cognitive deficiencies. Therapies that target select antigens overexpressed on only the malignant cells would alleviate some of these off-target side-effects. The Wagner lab has developed a non-genetic approach to facilitate selective cell-cell interactions using Chemically Self-Assembled Nanorings (CSANs). We have shown that functionalizing the CSAN construct with a cancer antigen-targeting protein and a T-cell targeting single chain antibody fragment (antiCD3 scfv) forms a multivalent, bispecific nanoring with the ability to traffic T-cells to the tumor. We therefore hypothesize that targeting overexpressed cancer antigens on medulloblastoma and/or glioblastoma using our technology would address many of the concerns associated with permanent genetic engineering such as CAR T cells.
Methods/Results: B7H3 (CD276) is a checkpoint molecule that is overexpressed on a wide variety of solid tumor types. For this study, we developed a new bispecific CSAN able to effectively direct human T cells to B7H3 overexpressing medulloblastoma. The Wagner lab is also currently able to produce CSANs that facilitate T cell interactions with many other solid tumor antigens such as EGFR and EpCAM. Therefore, we characterized the expression of EGFR, B7H3, and EpCAM on ONS76 and Daoy medulloblastoma and U87 glioblastoma in 2D and 3D models in vitro. We show that treating a B7H3+/EGFR+ allograft of ONS76 medulloblastoma with antiB7H3-CD3 or antiEGFR-CD3 CSANs resulted in ONS76 cytotoxicity and increased T cell lytic activity. We are currently analyzing the efficacy of our CSANs against orthotopically injected medulloblastoma in immunodeficient mice. We plan to probe the ways in which targeting these specific antigens induces changes in their expression within the tumor and identify potential modes of immune escape mechanisms such as antigen expression loss.
Conclusion: We show that bispecific CSANs are able to non-genetically direct T cells to selectively eradicate cancer cells overexpressing the targeted antigen. The conclusion of in vivo orthotopic models of medulloblastoma are required to demonstrate the ability of the CSANs to effectively cross the BBB and the efficacy of specifically targeting the checkpoint molecule B7H3.
Citation Format: Ellie Mews, Pauline Jackson, Ozgun Kilic, Justine Delgado, Mahathi Patchava, David Largaespada, Carston R. Wagner. Directing T cells using multivalent, bispecific chemically self-assembling nanorings (CSANs) to target brain tumors overexpressing EGFR and B7H3 antigens [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 1823.