MP: Humanization of CAR T-cell targeting Osteosarcoma

Immunotherapy is seen as the next generation therapy for the treatment of hard-to-beat cancers such as Osteosarcoma. It consists in guiding the patient immune system against it own tumour. To this end, specific cells known as effector immune cells are genetically modified to express specific receptor on their surface which will (1) guide them to the tumour and (2) trigger their functions which include target cell killing. These receptors should restrict their recognition to tumour cells only. A clinical receptor was recently demonstrated to be extremely efficient against blood cancer, it belongs to a family called "Chimeric Antigen Receptor" or "CAR". Due to their design, when CAR are transfer into patient immune cells, they are extremely efficient at recognizing cancer cells and stimulating immune cells. We have isolated two such molecules, OSCAR-1 and OSCAR-3, which have the unique faculty to recognize bone cancer (osteosarcoma) metastases in their most deadly form. We have shown that these two molecules can be expressed in immune cells. Our results clearly support that OSCAR-1 and 3 molecules represent a promising immunotherapy for the treatment of osteosarcoma. We are now planning an mRNA-based "safe" clinical trial of OSCAR-3 (the product will have a limited lifespan) which will give us information about the toxicity of the product. On the long term we want to provide a product which can be constitutively expressed (viral genetic transfer). In these conditions, we need to modify the construct and performed what is called a "humanization" of the gene. Indeed, one part of the original construct was isolated from a mouse protein. When injected into a human, it might evoke an immune response (xeno-response) against non-human molecule, which can lead to destruction of the CAR product by the immune system of the patient. This effect has been described and it is difficult to predict if one CAR will be more immunogenic than another. However, considering the cost and the effort to generate a CAR cellular product, changing the mouse part with a human part, thus annealing the anti-mouse response seems like a sound decision. Thus in agreement with our ambition to develop a safe product, we applied for support to change OSCAR-1 and -3 to human molecules, this process is called humanization. This will not only increase the safety by avoiding a rejection of the OSCAR-immune cells by the patient's immune system, but will also increase the value of our product in a commercial perspective. We have tested 8 molecules and have isolated 4 candidates for further development.

Outcomes: (1) We have filled new patents based on the hOSCAR sequences produced during this project. (2) We have also interacted with interested partners for the commercialization of the OSCAR products (original and humanized). (3) We have acquired new knowledge on humanization and may apply it to other CARs from our collection. The company which was involved in the design has proposed to join forces for this task which could be of interest for them to enter the CAR field and for us to obtain interesting pricing on our new orders. (4) We have isolated some clones (for OSCAR-1) which seems to have an increased functional avidity and could be even more attractive for future clinical use. Impacts: We have improved our product and come now with a complete collection of OS specific immunotherapeutic drugs.