Ludvig Sjöström - Institutionen för laboratoriemedicin

Title: CAR T cell strategies to address the biological challenges of acute myeloid leukemia

Main supervisor: Axel Hyrenius Wittsten

Reviewers: Sara Ek, Göran Karlsson, Niklas Landberg

Abstract

Background

Chimeric antigen receptor (CAR) T cell therapy has achieved major clinical success in a few hematological malignancies but has had limited success in acute myeloid leukemia (AML). AML is highly heterogeneous and includes immature and leukemia stem cell (LSC)-associated populations implicated in treatment resistance and relapse. A major challenge for CAR T cell therapy is the lack of suitable target antigens, as many AML-associated surface proteins are shared with normal hematopoietic stem and progenitor cells (HSPCs). This thesis explores complementary strategies to adapt CAR T cell therapy to the challenges of AML.

Research questions

1. Can CAR T cells be used for targeted hematopoietic conditioning prior to allogeneic hematopoietic stem cell transplantation (allo-HSCT) in AML?

2. Can combinatorial surface-antigen recognition improve CAR T cell selectivity for immature and LSC-associated AML?

3. Can CAR T cells exploit disease-associated surface antigens to target defined hematological malignancy subtypes?

Preliminary results

In Study I, KIT/CD117 was broadly expressed across genetically diverse AML and enriched in immature AML and normal hematopoietic progenitor compartments. A computationally de novo designed CD117 binder, DNB68, was incorporated into CARs and showed potent CD117-dependent activity in vitro and reduced bone marrow leukemia burden in vivo, further enhanced by CXCR4 co-expression. 

In Study II, complementary scRNA-seq, flow cytometry and CITE-seq analyses of primary AML BM samples and normal bone marrow (NBM) identified a combinatorial antigen signature enriched in immature and LSC-associated AML compared to NBM. The AND-gated LINK CAR system preferentially targeted double-positive AML cells, although single-antigen activity remains an ongoing engineering challenge.

In Study III, CAR T cells targeting a novel AML-associated antigen demonstrated potent antigen-dependent AML activity in vitro, with primary AML targeting and in vivo evaluation in planning.

Significance

AML relapse remains a major unmet medical need, and effective CAR T cell therapy has yet to be established in this disease. By addressing distinct barriers to CAR T cell therapy, this thesis seeks to contribute to the development of CAR T cell strategies for AML. Our preliminary results encourage us to further evaluate these approaches to improve CAR T cell selectivity and therapeutic applicability in AML.

Published studies

Study IV

Thorsson, H., Henningsson, R., Puente-Moncada, N., Peña-Martínez, P., Sjöström, L., Ågerstam, H., Sandén, C., Rissler, M., Castor, A., Marquart, H., Modvig, S., Paulsson, K., Pronk, C. J., Schmiegelow, K., Hyrenius-Wittsten, A., Orsmark-Pietras, C., Lilljebjörn, H., & Fioretos, T. (2024). Single-cell genomics details the maturation block in BCP-ALL and identifies therapeutic vulnerabilities in DUX4-r cases. Blood, 144(13), 1399–1411. https://doi.org/10.1182/blood.2023021705