Abstract 3609: Chimeric cytokine receptors increase memory phenotypes and improve expansion and efficacy of CAR-T cell therapies

Abstract Cytokine activation of T cells can promote T cell proliferation, memory and improve T cell function in driving tumor cell killing. However, systemic administration of cytokines at therapeutic doses is also associated with unacceptable toxicities. To overcome this limitation, we have engineered a system of private cytokine signaling to affect T cell homeostasis, identity, and function. Specifically, we have engineered chimeric cytokine receptors (CCRs) composed of single-chain variable fragments (scFvs) that bind specifically to small molecules such as fluorescein or DOTA. These scFvs are fused to transmembrane and intracellular domains of all members of the common gamma-chain (γ-chain) family of cytokine receptors. CCRs that permit private cytokine signaling were introduced into known CAR-T cell therapies and their impact on CAR-T cell phenotype, function, and anti-tumor activity was tested. First, CCR-containing T cells were tested for activation-induced changes in phenotype and expansion following stimulation with small molecule conjugates in vitro. The most promising results were obtained using either the IL-7Rα- or IL-2Rβ/γ-containing CCR’s. CCR-containing constructs were then transduced into one of two different anti-BCMA CAR-T constructs, ide-cel or cilta-cel, using a lentiviral transduction system. CAR-T cells containing each CCR were then compared with CAR-T cells lacking CCRs for phenotype and function in vitro. Results indicated that engineering the IL-7Rα CCR with both of these CAR-T’s led to increased expansion, cytokine secretion and improved tumor cell killing. Next, CAR-T cells expressing the IL-7Rα CCR were compared to CAR-T cells lacking CCR for efficacy and durability in a mouse model of human multiple myeloma. IL-7Rα CCR-expressing CAR-T cells demonstrated improved long-term tumor control compared to ide-cel and cilta-cel alone. In addition, IL-7Rα CCR-expression increased T cell numbers in blood, spleen and bone marrow of tumor-bearing mice. These increases were particularly evident in the CD8+population of CAR-T cells in vivo. These results demostrate that private cytokine signaling using small-molecule activatable CCRs can improve efficacy and durability of CAR-T cells. We are testing these CCRs in mouse models of human solid tumors to assess their ability to overcome the immunosuppressive microenvironment. Citation Format: John R. Newcomb, Jun Ren, Sakeena Syed, Zachary Caruolo, Lindsay Webb, Craig McKay, Stephanie Kwei, Carl Novina, Fred Mermelstein. Chimeric cytokine receptors increase memory phenotypes and improve expansion and efficacy of 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 3609.