Abstract 6398: Harnessing the conditional proteolytic activity of ADAM17 to generate autonomous regulatory mechanisms in CAR T cells

Abstract Background and Purpose: Sustained and unregulated expression of CARs on the surface of T cells can result in reduced potency via exhaustion as a result of tonic signaling or prolonged response to high levels of antigen encountered in vivo. To curtail this phenomenon, we have developed the Activation Induced Release (AIR) system, a novel regulatory platform that exploits activation induced regulation of the ADAM17, to cleave proteins from the surface following activation of the T cell. We hypothesized that AIR-controlled CARs would “self-regulate” the density of CARs on their surface and thereby endogenously ameliorate the effects of tonic signaling. This system would allow for rapid and reversible protein-level regulation of functional receptors without the need for small molecule addition or the incorporation of separate exogenous regulatory genes. Methods and Results: To ascertain the effects of the AIR platform on reducing tonic signaling and improving CAR T cell function, we generated AIR versions of several tonic signaling-prone CARs targeting GD2, B7H3, and Her2 by imputing a hinge motif from CD62L, an endogenous ADAM17 substrate. All AIR-regulated CARs demonstrated reduced rates of tonic signaling, resulting in enhanced functionality over traditional CARs. This improvement was associated with AIR-CARs’ enhanced proliferative capacity, higher expression of memory markers CD62L and IL7R, and lower expression of exhaustion and activation markers CD25, CD39, TIM-3, and PD-1. AIR-GD2 CARs also demonstrated enhanced tumor control in a Nalm6 leukemia mouse model. Conclusions: The AIR platform offers a simple approach to ameliorate the issues resulting from tonic signaling, broadening the scope of CARs that can be utilized in the clinic, as well as the types of antigens that can be targeted in both liquid and solid tumor settings. The AIR system offers a unique approach to CAR T cell engineering, allowing for dynamic control over receptor expression through the use of an endogenous regulatory circuit and minimal alteration to the desired exogenous protein. Citation Format: Jeremy R. Bjelajac, Adria Canellas Socias, Jennifer Hamad, Preeti Nehra, Meena B. Malipatlolla, Peng Xu, Sean Alexander Yamada-Hunter, Louai Labanieh, Elena Sotillo, Crystal L. Mackall. Harnessing the conditional proteolytic activity of ADAM17 to generate autonomous regulatory mechanisms in CAR T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6398.