Abstract 58: Immunocytokines with specificity for invariant region of CAR molecules enhance effector function of multiple CAR T cell therapies

Abstract The effector functions of CAR T cells can be enhanced through delivery of immunostimulatory cytokines, such as IL-12, IL-18, or IL-23. However, systemic delivery of recombinant cytokines or paracrine secretion by CAR T cells can elicit toxicities due to non-specific targeting of the cytokines. Here, we designed immunocytokines with antibodies specific for the invariant linker peptides that join variable domains in the CAR scFv and immunostimulatory cytokines. The immunocytokines were capable of targeting CAR molecules agnostic of target antigen, demonstrating broad applicability without the need for further genetic engineering of CAR therapies, such as co-expression of a surrogate molecule (tEGFR, etc. ). The addition of immunocytokines enhanced CAR T cell cytolytic activity and secretion of type I cytokines, even at low concentrations of immunocytokine. In a stringent Nalm6 xenograft model, the addition of immunocytokines delivering IL-12 enhanced the anti-tumor activity of anti-CD19 CAR T cells and overall survival compared to controls of antibody alone or PBS. This technological development presents the opportunity to specifically enhance the activity of multiple CAR T cell therapies in the absence of non-specific toxicities. Citation Format: J T. Keane, Oula K. Dagher, Fang Liu, Avery D. Posey. Immunocytokines with specificity for invariant region of CAR molecules enhance effector function of multiple CAR T cell therapies abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 58.