Activation of Cell Intrinsic Signaling in CAR-T cells via a Chimeric IL7R Domain.

Chimeric Antigen Receptor (CAR)-T cells can effectively treat leukemias, but sustained anti-tumor responses can be hindered by a lack of CAR-T cell persistence. Cytotoxic effector T cells are short-lived, and establishment of CAR-T cells with memory to ensure immune surveillance is important. Memory T cells depend on cytokine support, with IL7 activation of the IL7 receptor being critical. However, IL7 receptor surface expression is negatively regulated by exposure to IL7. We aimed to support CAR-T persistence by equipping CAR-T cells with a sustained IL7Rα signal. We engineered T cells to constitutively secrete IL7 or to express an anti-AML-targeted IL7Rα-Chimeric Cytokine Receptor (CCR) and characterized the phenotype of these cell types. Canonical downstream signaling was activated in CCR-T cells with IL7R activation. When co-expressed with a cytotoxic CAR, functionality of both the CCR and CAR was maintained. We designed hybrid CAR-CCRs and note membrane proximity of the intracellular domains as vital for signaling. These data show cell-intrinsic cytokine support with canonical signaling and functionality can be provided via expression of an IL7Rα-domain whether independently expressed or incorporated into a cytotoxic CAR for use in anti-cancer therapy.