Emerging synthetic receptor designs allow for complex, user-defined programs to be engineered into mammalian cells. Chimeric Antigen Receptors (CARs) allow for T cell activation to occur following antigen recognition, a remarkable immunotherapy that is being refined to achieve efficacy against solid cancers. With the growing number of promising tumour-associated antigens identified, it is essential to adopt new technologies to mitigate off-tumour toxicity risks.
Versatile Proteolysis Receptor CARs (VIPERs) are modified CARs that can be switched off using a stop compound, Grazoprevir (FDA approved antiviral). Since 2022, only CD19 targeting VIPER T cells have been published. After confirming that CD19 VIPERs kill CD19+ NALM6 tumour cells as effectively as a standard CD19 CAR, we developed 2 novel VIPERs that target glioblastoma. Our cell surface proteomics dataset validates that both antigens are abundant on primary glioblastoma tissue, with one antigen being very novel as it is yet to be targeted using cell therapies. Targeting this antigen our CD8+ VIPER T cells could kill U251 and A172 glioblastoma cell lines in vitro, and can be switched off in the presence of 1µM Grazoprevir. Future work will interrogate the in vivo efficacy using orthotopic glioblastoma models. We have also expanded out VIPER mediated in vitro killing to examine its’ efficacy against HCT-116 (CRC) and MDA-231-HM (TnBC) models, suggesting potential as a pan-cancer immunotherapy.
Synthetic Intramembrane Proteolysis Receptors (SNIPRs) induce transgene expression after antigen encounter, therefore can restrict CAR T cell cytotoxicity to tumour location. We created a glioblastoma targeting SNIPR library (n=4,814) and are individually validating hits, with one novel SNIPR specifically inducing fluorescent reporter expression after co-culture with glioblastoma cells.
We envision that SNIPR mediated induction of VIPER components will achieve a sophisticated cellular program that displays reduced systemic toxicity risks, therefore facilitates development of potent, yet safe, brain cancer immunotherapies.