RIPECROP · RNA-based cancer ImmunotheraPeutics to Enhance CROssPrimming

Cancer immunotherapy achieves unprecedented efficacy against a number of malignant diseases. Preclinical experiments in mouse models conclude that type-1 dendritic cells (cDC1) that present tumor antigens are an absolute requirement for most immunotherapy strategies to be efficacious, including those routinely applied to cancer patients at present. cDC1 cells are specialized in redirecting engulfed cell-associated antigens to the class I MHC antigen-presentation pathway in the context of IL-12 production and co-stimulation, at least when cDC1 cells are in the presence of moieties denoting viral infection. Such phenomena are key to prime anti-tumor T lymphocytes through a mechanism known as crosspriming. The RIPECROP project will test immunotherapy agents that enhance the numbers and performance of cDC1 in the tumor tissue microenvironment. The strategies will be based on mRNA constructs that will encode engineered forms of the cDC1 growth factor sFLT-3L, single-chain interleukin-12, cDC1 specific chemoattractants and bispecific costimulatory ligands targeted to surface proteins of cDC1 cells. The new therapeutic agents in the form of coding mRNAs will be expressed in vivo either intratumorally or using the mRNA-transferred liver as an internal biofactory to systemically produce the encoded proteins and their combinations. Innovative in-vivo screenings based on hydrodynamic gene transfer of the liver with various expression plasmids encoding heterodimerization systems will be performed to identify suitable new mRNA-based immunotherapeutic chimeric constructs to enhance antitumor T-cell crosspriming. Overall, a novel mRNA-based toolbox will be studied both in terms of anti-tumor efficacy and regarding the mechanisms of action, in such a manner, that crosspriming will become exploitable in combinatorial approaches for cancer immunotherapy.