Specific Immunotherapeutic Targeting of Glioblastoma using the switchable RevCAR NK-92 Cell System

Chimeric antigen receptor (CAR)-expressing immune cells, such as CAR Natural Killer (NK) cells and CAR NK-92 cell lines have shown promising therapeutic potential over the past years against solid tumors. Targeting Glioblastoma (GBM) with conventional CAR therapies is still challenging due to the sophisticated tumor microenvironment, antigen escape, and on-target/off-tumor toxicity. Therefore, our project aims to develop a safer and more flexible adapter CAR NK-92 platform, called the Reverse CAR (RevCAR) NK-92 system, which consists of two components, the RevCAR NK-92 cell expressing an extracellular short peptide epitope and a bispecific Rev Target Module (RevTM) that redirect the RevCAR NK-92 cells to tumor cells. Only upon this cross-linkage, redirected RevCAR NK-92 cells are activated to lyse tumor cells. The fibroblast growth factor-inducible 14 (Fn14) surface receptor is a promising target antigen overexpressed on GBM. Therefore, we have developed Fn14-specific RevTM to specifically redirect RevCAR NK-92 cells against Fn14-expressing GBM cells. Through in vitro and in vivo analyses, we assessed the cytotoxic effect of our system on GBM and showed for the first time that GBM cells were efficiently killed by redirected RevCAR NK-92 cells using the novel Fn14-specific RevTM in picomolar concentration, and that the tumor cell killing was associated with increased IFNγ secretion. Hence, these findings give an insight into the clinical potential of the RevCAR NK-92 system as a safe and specific immunotherapy against glioblastoma.