CAR T-cells targeting FLT3 have potent activity against FLT3-ITD+ AML and act synergistically with the FLT3-inhibitor crenolanib

Leukemia. 2018 May;32(5):1168-1179. doi: 10.1038/s41375-018-0009-0. Epub 2018 Feb 5.

Abstract

FMS-like tyrosine kinase 3 (FLT3) is a transmembrane protein expressed on normal hematopoietic stem and progenitor cells (HSC) and retained on malignant blasts in acute myeloid leukemia (AML). We engineered CD8+ and CD4+ T-cells expressing a FLT3-specific chimeric antigen receptor (CAR) and demonstrate they confer potent reactivity against AML cell lines and primary AML blasts that express either wild-type FLT3 or FLT3 with internal tandem duplication (FLT3-ITD). We also show that treatment with the FLT3-inhibitor crenolanib leads to increased surface expression of FLT3 specifically on FLT3-ITD+ AML cells and consecutively, enhanced recognition by FLT3-CAR T-cells in vitro and in vivo. As anticipated, we found that FLT3-CAR T-cells recognize normal HSCs in vitro and in vivo, and disrupt normal hematopoiesis in colony-formation assays, suggesting that adoptive therapy with FLT3-CAR T-cells will require subsequent CAR T-cell depletion and allogeneic HSC transplantation to reconstitute the hematopoietic system. Collectively, our data establish FLT3 as a novel CAR target in AML with particular relevance in high-risk FLT3-ITD+ AML. Further, our data provide the first proof-of-concept that CAR T-cell immunotherapy and small molecule inhibition can be used synergistically, as exemplified by our data showing superior antileukemia efficacy of FLT3-CAR T-cells in combination with crenolanib.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Benzimidazoles / therapeutic use
  • Cell Line, Tumor
  • Drug Synergism
  • Hematopoietic Stem Cell Transplantation / methods
  • Humans
  • Immunotherapy, Adoptive / methods*
  • Leukemia, Myeloid, Acute / therapy*
  • Piperidines / therapeutic use
  • Receptors, Chimeric Antigen / immunology
  • Receptors, Chimeric Antigen / therapeutic use*
  • Tandem Repeat Sequences / genetics
  • Tumor Cells, Cultured
  • fms-Like Tyrosine Kinase 3 / antagonists & inhibitors
  • fms-Like Tyrosine Kinase 3 / genetics
  • fms-Like Tyrosine Kinase 3 / immunology*

Substances

  • Benzimidazoles
  • Piperidines
  • Receptors, Chimeric Antigen
  • fms-Like Tyrosine Kinase 3
  • crenolanib