Adapter-CAR-T-cells versus Acute Myeloid Leukemia and Leukemia Stem Cells

• Applicant: Dr. Christian Seitz, since 2/2021
• Subject Area: Hematology, Oncology ; Pediatric and Adolescent Medicine
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 411791562

T cells, redirected by chimeric antigen receptors for antigen-specific tumor cell elimination, have revolutionized the therapy of B-phenotypic acute lymphoid leukemia (ALL). In contrast to ALL, clinical translation of CAR-T cell therapy for acute myeloid leukemia (AML) is more complicated. This is mainly due to the fact that most AML associated antigens are also expressed on vitally sensitive tissues, particularly on cells essential for myelopoiesis, and due to heterogeneous antigen expression in general. Consequently, the development of controllable as well as flexible CAR-systems is crucial for safety and efficacy. Synchronic multiple targeting is required to address the entirety of AML blasts and to avoid the development of resistance to therapy due to antigen loss. Controllable activity as well as reliable termination of therapy is indispensable to be able to especially prevent severe or even lethal myelotoxicity due to elimination of myeloid precursor cell. The important characteristic of our adapter-CAR T cell system (aCAR-T) is the disconnection of antigen recognition and CAR activation. aCAR-Ts can only be activated and exert function in the presence of specific adapter molecules, which mediate the antigen-specific binding of aCAR-T to the target cell. Due to this mechanisms, aCAR-Ts can be switched on and off easily. Moreover, target antigens can be individually targeted and combined (One for all).In the current study, we will perform a comprehensive qualitative and quantitative as well as a functional analysis of 20 potential AML associated target antigen on cell lines and primary patient samples. The efficacy of antigen specific adapter molecule mediated lysis of AML blasts by aCAR-Ts in single as well as combinatorial treatment will be evaluated. Moreover, model systems for antigen shift and antigen loss will be generated by CRISPR/Cas9 induced knock out of target antigens in order to demonstrate the advantages of synchronic multiple targeting. Based on the in vitro results, consecutive in vivo evaluation will be performed aiming for complete leukemia eradication by specifically selected combinations of adapter molecules. The reversibility of aCAR-T mediated toxicity against human hematopoiesis will be demonstrated in a humanized mouse model by transient application of adapter molecules. Finally, individualized therapy stratification will be performed in an autologous patient specific (primary AML blasts and aCAR-T generated from the patient’s T cells) xenograft model. The goal of these co-clinical “avatar-trials” is to evaluate the best possible combination of adapter molecules in order to complement antigen expression with a predictive immunotherapy profile. This data will help to understand the course of the disease under aCAR-T therapy and serve as a guidance to schedule therapy in case of a relapse. The results obtained in this preclinical study will directly translate into an investigator initiated clinical trial.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Dr. Patrick Schlegel, from 3/2020 until 2/2021