Engineering the TG6002 vaccine virus for improved cancer killing abilities – OncoVaccine

The OncoVaccine research project will be jointly conducted at Transgène SA, the Institut de Génétique et de Biologie Moléculaire et Cellulaire (UMR7104 CNRS/UdS Inserm U964, Illkirch, France) and at the Laboratoire de Biotechnologies et Signalisation Cellulaire (IREBS, UMR 7242, Illkirch, France) and brings together with Transgène SA R&D departments three different groups of these two research units:
- The “High Throughput Cell-based Screening facility” headed by Dr Laurent Brino (IGBMC)
- The “Laboratoire de bioinformatique et de génomique intégratives” headed by Dr Olivier Poch (IGBMC)
- The “Immunobiotechnologie” team headed by Pr Etienne Weiss (IREBS)

Cancer is the second leading cause of death in developed countries after cardiovascular disease. Conventional treatments of many cancers (i.e. pancreatic, lung, brain, cervical cancers) by radio-therapy, chemo-therapy and surgery have reached their limits of effectiveness, calling for urgently needed novel therapeutic strategies.
Oncolytic viruses (OVs) are strongly emerging as alternative cancer therapies. By definition, these viruses demonstrate significant replication and destruction of neoplastic tissues with little pathology to normal ones. Although recent progresses have been made in the field with the development of second generation armed oncolytic vectors, there is still a need to design new improved viruses that could overcome cancer cells resistance to cytolysis.
The main objective of this project is to develop a new generation of oncolytic vaccinia viruses (VACV) that express a molecular recombinant tool promoting the loss of function of host cell factors involved in cellular resistance to cytolysis. As the replication of VACV occurs in the cell cytoplasm, a small hairpin RNA-based knockdown strategy is not possible. Thus, the strategy chosen in this project is to design VACVs expressing a soluble ScFv intrabody (“Intra-solubodies molecular tool”) directed against host cellular targets implicated in resistance to viral cytolysis.

The main steps of this program are as follows:
- Identify pathways and host cell genes which, when silenced with siRNAs, potentiate the cytopathic effect of a VACV in a tumoral cell line resistant to infection (cytopathy sensitizers). This will be performed by screening a siRNA library targeting the human genome in combination with VACV infection on the pancreatic Mia-Paca-2 cancer cell line.
- Identify resistance factors and select targets by a secondary RNAi screen confirming the oncotropic cytopathic effect of the target silencing in several cancer cell lines, but not in primary cells.
- Identify recombinant target relocalizing intrabodies mimicking siRNA knockdowns. These intrabodies will contain a cellular localization signal that will relocate the target protein to cell compartments in which it will not be able to exert its function.
- Generate a new generation of improved TG6002-derived VACVs expressing recombinant target relocalizing intra-solubodies. The therapeutic activity of these new viruses will be evaluated in vitro on cancer cell lines and in vivo in xenografted cancer mouse models.
The combination of the results obtained by the siRNA and intrabodies screens will give us a unique opportunity to identify in unbiased manner key cellular components implicated in the mechanisms of resistance towards VACV infection and cytopathic activity. The success of the project is expected to have a significant impact on several areas of oncotherapy and would be a new hope for cancer patients as well as a strong competitive advantage for our company Transgène SA.