Abstract 5746: Flexible tumor-specific cytokine and antigen delivery through the T-SIGn vector platform enables effective CAR-T cell therapy against solid tumors
Authors: Sasso Maria Stella , Bergin Rachel , Lear Rochelle , Plumb Darren , Zonca Manuela , Vainiute Eva , Snowden Meg , Jang Tae Hyun , Muntzer Alice , Cerqueira Carla C. , West Katy , Bucktrout Samantha , Champion Brian R. 
Published: April 2023

Abstract
Efficacy of Chimeric Antigen Receptor (CAR) T cell therapy against solid tumors is hampered by multiple barriers, including tumor-associated immunosuppression, poor CAR-T cell trafficking into solid tumor masses and shortage of highly expressed cancer-specific target antigens. The T-SIGn (Tumor Specific ImmunoGene) platform generates viral vectors that can produce combinations of transgenes selectively within the tumor microenvironment (TME). T-SIGn is clinically validated for intravenous (i.v.) delivery, enabling vectors to reach primary and metastatic sites to produce their therapeutic payloads specifically in malignant epithelial cells. Using an A549 human tumor xenograft and metastasis model, we previously demonstrated that i.v. administration of a T-SIGn vector encoding IFNα, MIP1α and CD80 results into potentiated CAR-T cell activation and therapy efficacy (Sonzogni et al. 2022). Here, we further evaluated the potential of T-SIGn combination with Cell Therapy by investigating the impact on CAR-T cell activity of vectors encoding different arrays of cytokines and chemokines. Using an in vivo A549 model and anti-HER2 CAR-T cells in NSG mice, we demonstrated that T-SIGn vectors can enable effective CAR-T cell therapy against solid tumors by providing diverse localized cytokine/chemokine-mediated T cell boosting, with IL-12-encoding vectors resulting in complete and durable tumor clearance. Furthermore, we explored the use of the T-SIGn platform to encode secreted bispecific “adaptor” molecules able to simultaneously bind to a tumor surface antigen and to a CAR specific for an antigen not naturally expressed by the tumor, allowing the redirection of CAR-T cells against desired tumor types. We designed a vector (NG-1125) encoding an anti-HER2 ScFv_CD19 bispecific construct as a model “adaptor” molecule, together with IFNα and CXCL9, and we showed that this construct can effectively redirect anti-CD19 CAR-T cell against HER2+CD19− tumor cells. In vitro X-CELLigence-based cytotoxicity assays demonstrated killing of both HER2+CD19− A549 and SKOV3 cells by anti-CD19 CAR-T cells in presence of vector-derived anti-HER2 ScFv_CD19. Following i.v. NG-1125 dosing of A549 tumor-bearing mice, ex vivo flow cytometry analysis of tumor masses revealed binding of the encoded adaptor molecule to both vector-infected and uninfected tumor cells. Furthermore, in vivo NG-1125 administration together with anti-CD19 CAR-T cells resulted into increased intra-tumoral densities of transferred T cells. Collectively, these data show the potential of T-SIGn vectors in overcoming solid tumor resistance mechanisms to CAR-T and pave the way for the development of other immunotherapeutics to be expressed within the TME via T-SIGn vectors in combination with CAR or TCR-based therapies.
Citation Format: Maria Stella Sasso, Rachel Bergin, Rochelle Lear, Darren Plumb, Manuela Zonca, Eva Vainiute, Meg Snowden, Tae Hyun Jang, Alice Muntzer, Carla C. Cerqueira, Katy West, Samantha Bucktrout, Brian R. Champion. Flexible tumor-specific cytokine and antigen delivery through the T-SIGn vector platform enables effective CAR-T cell therapy against solid tumors. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5746.