Development of Novel Anti-CD10 Target Modules for Redirection of Universal CAR T Cells Against CD10-Positive Malignancies

The common acute lymphoblastic leukemia antigen CD10 is a marker for several hematological malignancies, including acute lymphoblastic leukemia as well as T and B cell lymphomas, Burkitt lymphomas, and some solid tumors like renal cell carcinomas, pancreatic tumors and melanomas. Because of its tumor related expression pattern, CD10 is an attractive target for adoptively transferred T cells that are genetically modified to express chimeric antigen receptors (CARs). Recently, conventional CAR T cell therapy targeting CD19-positive hematological malignancies was clinically approved because of its impressive effectiveness in patients. However, CAR T cells can also cause severe side effects like on-target, off-tumor reactions, tumor lysis syndrome and cytokine release syndrome. Most critically, activity of conventional CAR T cells cannot be controlled, once they are applied in patients. As CD10 is also widely expressed on normal tissues, CAR T cell reactivity has to be controllable in order to stop CAR T cell therapy in case of on-target, off-tumor toxicities occur. Especially for this purpose, we have recently established a switchable, modular and universal CAR platform technology, named UniCAR system, which can be repeatedly turned on and off.

In contrast to conventional CARs, that directly recognize a tumor-associated antigen (TAA) on the tumor cell surface via their extracellular single-chain variable fragment (scFv), the UniCAR system is structured in a modular manner of two components. The first component are T cells genetically engineered to express UniCARs and the second component are target modules (TMs). Most importantly, UniCARs cannot directly bind to a TAA because their extracellular scFv is directed against the peptide epitope E5B9 which is not present on the surface of living cells. Consequently, UniCAR armed T cells are per se inert. They can be redirected towards tumor cells only via a TM. TMs consist of a scFv targeting a TAA and the epitope E5B9 recognized by UniCARs allowing a cross-linkage of UniCAR T cells with tumor cells which results in T cell activation. As TMs have a very short half-life, UniCAR T cell activity can be controlled by dosing of the TM. Once the TM is administered, UniCAR T cells can be switched on, but once the TM injection is stopped and the TM is eliminated, UniCAR T cells are switched off immediately.

Here, we show proof of concept for functionality of the UniCAR system targeting CD10-positive malignancies. Therefor, a novel anti-CD10 TM was constructed which is able to redirect UniCAR T cells to eliminate CD10-expressing tumor cells.

In summary, we have established a universal, switchable, modular UniCAR platform technology that can be used to target CD10-positive malignancies.