Enhancing CD123-directed CAR T-cell efficacy to overcome cytokine-mediated resistance mechanisms in AML

• Applicant: Dr. Andreas Riedel
• Subject Area: Hematology, Oncology
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 576727415

Chimeric antigen receptor (CAR) T cell therapy has revolutionized the treatment of relapsed and refractory B-cell malignancies, but its efficacy in acute myeloid leukemia (AML) remains limited due to multiple intrinsic resistance mechanisms, e.g. immune evasion, and an immunosuppressive microenvironment dominated by myeloid-derived suppressor cells. Recent work by the host laboratory (S. Gill, UPenn) has uncovered a cytokine-mediated resistance pathway in AML, whereby IL-3, GM-CSF, and FLT3L secreted during CAR T cell activation support leukemic cell survival via JAK1/2-STAT3/5 signaling, contributing to CAR T cell exhaustion and subsequent therapy failure. Notably, this mechanism is absent in B-ALL, highlighting its disease specificity. Inhibiting this pathway with ruxolitinib (JAK1/2 inhibitor) restores CAR T cell efficacy in vitro and in vivo but compromises T cell proliferation and cytokine signaling, raising concerns about long-term efficacy. The project addresses the dual challenge of overcoming cytokine-mediated AML resistance and preserving CAR T cell fitness in multimodal settings. It is structured in two main objectives. Objective 1 aims to (i) characterize the impact of selective JAK inhibition (JAK1: itacitinib; JAK2/FLT3: pacritinib; JAK1/2: ruxolitinib) on CD123-targeted CAR T cell function; and (ii) to engineer ruxolitinib resistant CAR T cells via CRISPR base/prime editing to maintain JAK signaling in immune effector cells while exploiting JAK inhibition in leukemic blasts. In objective 2 we will develop CAR T cells with disrupted secretion of IL-3, GM-CSF, and FLT3L to block the identified cytokine-mediated resistance pathway without systemic JAK inhibition. This approach aims to modulate the immunosuppressive AML microenvironment while preserving CAR T cell proliferation and cytotoxicity. This proposal combines synthetic biology, immune engineering, and leukemia biology to pioneer strategies that improve CAR T cell function in AML. By selectively engineering therapeutic resistance or cytokine deletion, the study will try to 1) enhance the efficacy of CAR T cells in a notoriously resistant entity, 2) reduce toxicity and immune suppression associated with JAK inhibition, and 3) lay the groundwork for next-generation CAR T cell platforms suitable for combinatorial therapies.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Professor Saar Gill, Ph.D.