A multifunctional linker for chimeric antigen receptor T-cells

Chimeric antigen receptors (CARs) have been developed for the molecular engineering of effector T-cells to be used in targeted cancer therapy. CARs consist of the antigen-binding single-chain fragment (scFv) of an antibody fused via a hinge region to a transmembrane domain (TM) and to one or more intracellular signalling co-stimulatory regions. CAR expressing T-cells are now able to specifically (and in a major histocompability complex-independent manner) recognize the corresponding tumor-associated antigens. The different scFv-regions determine the specifity and affinity of the CARs. Hundreds of different CARs have been generated with the clinically most successful so far being CAR constructs that recognize the B-cell-associated antigen CD19 on leukemias and lymphomas. The hinge region in CARs functions as a flexible spacer for the scFvs and improves the recognition/function of CARs for antigens closer located to the surface of target cells. For a large number of constructs, the hinge region consists of the CH2CH3 domain of a human IgG antibody. This can bind to Fcg-receptors on macrophages and other cells. The result is cross-activation and activation-induced cell death in vivo independent of recognition of the target antigen. Researchers of a German university have replaced the CH2CH3 site by fragments of the human CD34 antigen that contain the epitope for the CD34 antibody QBEND10 that is used in a device already available on the market. This exchange has decisive benefits: On the one hand unwanted immune side-effects are potentially prevented. On the other hand modified T cells can be easily detected using standard flow cytometry. Thus engraftment and persistence of transduced T-cells in vivo can be readily assessed. Ultimately, using this hinge domain, modified T-cells can easily and rapidly be selected and enriched by the available system for clinical use. By including this hinge region in CAR constructs for selection, common viral and also nonviral vectors for CAR transfer have sufficient space for the introduction of a safety switch that facilitates the use of allogeneic or even haploidential donor effector cells. The university seeks licensees with activities in the area of immunotherapy, who would like to implement the research results. Within this co-operation further therapeutic development is also possible.