Antigen-specific redirection of off-the-shelf NK-92 cells using the universal CAR platform ‘‘UniCAR’’

Modifying of immune effector cells with chimeric antigen receptors (CARs) has revealed a promising therapeutic potential for targeting cancer, especially with CAR-modified T cells. However, the use of other immune cells like primary NK cells or NK cell lines appeared as another advantageous approach that can be combined with CAR technology. Unlike T cells, established NK cell lines can be used allogenically as an off-the-shelf product with reduced risk of toxicities. We have established previously a modular Universal CAR platform (UniCAR) which can be switched on/off and allows the flexible targeting of various tumor antigens. This system consists of two parts, the UniCAR-expressing immune effector cells and a target module (TM). The UniCAR-immune cells cannot recognize surface antigens but are only redirected with the TM which contains an antigen-binding moiety on one hand and an epitope recognized by the UniCAR molecules on the other hand. Here, we provide a proof of concept for using the UniCAR system in combination with the NK-92 cell line to target disialoganglioside GD2-expressing tumors. The UniCAR NK-92 cells induced increase in lysis of neuroblastoma and melanoma cell lines in the presence of scFv- or human IgG4-based TMs, associated with specific release of pro-inflammatory cytokines. Moreover, UniCAR NK-92 cells were shown to be functional in eradicating GD2-expressing tumors in experimental mice. In order to investigate the in vivo half-life of the scFv- and IgG4-based TMs, they were radiolabeled with 64Cu and detected using PET imaging. Dynamic PET scanning has shown that the IgG4 format increased the half-life of the TM to around 24 folds in comparison to the scFv-based TMs. In summary, UniCAR NK-92 provides an off-the-shelf universal platform that can be combined with various antibody formats, and can be easily expanded for therapeutic use.