Switching CAR T cells on and off: a novel modular platform for retargeting of T cells to AML blasts.

M Cartellieri,M Von Bonin,G Ehninger,S Koristka,M P Bachmann,E P Bejestani,A Ehninger,C Arndt,S Loff,A Feldmann

doi:10.1038/bcj.2016.61

Abstract

The adoptive transfer of CD19-specific chimeric antigen receptor engineered T cells (CAR T cells) resulted in encouraging clinical trials in indolent B-cell malignancies. However, they also show the limitations of this fascinating technology: CAR T cells can lead to even life-threatening off-tumor, on-target side effects if CAR T cells crossreact with healthy tissues. Here, we describe a novel modular universal CAR platform technology termed UniCAR that reduces the risk of on-target side effects by a rapid and reversible control of CAR T-cell reactivity. The UniCAR system consists of two components: (1) a CAR for an inert manipulation of T cells and (2) specific targeting modules (TMs) for redirecting UniCAR T cells in an individualized time- and target-dependent manner. UniCAR T cells can be armed against different tumor targets simply by replacement of the respective TM for (1) targeting more than one antigen simultaneously or subsequently to enhance efficacy and (2) reducing the risk for development of antigen-loss tumor variants under treatment. Here we provide ‘proof of concept' for retargeting of UniCAR T cells to CD33- and/or CD123-positive acute myeloid leukemia blasts in vitro and in vivo.

Highlights

Adoptive T-cell therapy with chimeric antigen receptor (CAR) engineered T cells (CAR T cells) has recently shown encouraging clinical results in B-cell malignancies
Approximately onethird of patients treated in recent trials experienced severe fevers and inflammations and all patients suffer from ongoing B-cell aplasia, as long as CD19-specific CAR T cells are present in their circulation
In order to facilitate the fluorescence-activated cell sorting (FACS) analysis of UniCAR expression on the surface of transduced T cells, we fused another peptide epitope of 18 amino acids (E-tag18) and an additional linker consisting of four glycines followed by one serine (G4S1) between the UniCAR single-chain fragment variable (scFv) and the CD28 coding region

Summary

INTRODUCTION

Adoptive T-cell therapy with chimeric antigen receptor (CAR) engineered T cells (CAR T cells) has recently shown encouraging clinical results in B-cell malignancies. A recent in-depth analysis on 4300 patient samples revealed that CD33 and CD123 are expressed either in combination or alone on nearly 100% of all AML blasts.[11] Both antigens seem to be ideal targets for immunotherapy.[12,13] redirecting T cells against CD33 or CD123 with single-specific CARs for AML treatment is hampered by the fact that both antigens are expressed on AML blasts, but are present on hematopoietic stem cells, on progenitor and mature hematopoietic cells of the myeloid lineage and on endothelial cells.[14] To extend the application range of CAR T cells, we developed a flexible modular CAR platform (UniCAR). Were labeled with live cell-dye eFluor 670 (eBioscience, Frankfurt, Germany) to distinguish them from effector cells

MATERIALS AND METHODS

RESULTS

Findings

CONFLICT OF INTEREST