Optimalisering: CAR T-CELL THERAPY FOR OSTEOSARCOMA

Osteosarcoma (OS) is a cancer type which affects both young and old people. Among children it is the eighth most common form of cancer. OS is an aggressive disease which often kills, or leaves the patients heavily affected by the treatment. Indeed, early diagnostics could improve prognosis, however, OS detection is not straightforward and solutions reside in heavy treatments such as orthopaedic surgery where amputation is sometimes necessary to cure or prolong lifespan. In the 1970's chemotherapeutic drugs were introduced and showed an important improvement in terms of patient survival, but unfortunately some patients still succumb to the spreading of the tumour, in particular with lung metastases. It was recently reported for blood cancers that a novel type of molecule known as Chimeric Antigen Receptor (CAR) could rescue patients otherwise condemned. The results published by different groups worldwide demonstrated unprecedented effects in certain hard-to-treat cancers. CAR therapy relies on the use of the immune system of the patient. The immune system protects the body against external invaders such as virus and bacteria, but also eliminates cancer cells. The foot soldiers of this system are the called leukocytes, in particular the T cells which are able, upon specific recognition of an abnormal cell, to kill it. Yet, some threats manage to go under the immune radar, hence people still die from infections affecting the immune system (e.g. HIV) or some cancers. A CAR molecule helps the immune cells to recognize specific markers (antigens) on the surface of the tumour. This recognition will stimulate a complex signaling cascade that will finally lead to the cancer cell killing. CAR recognize surface molecules which are specific for the cancers. The present project was built on antibody molecules isolated more than 30 years ago in our hospital, TP-1 and TP-3. These had the capacity to specifically bind OS lung metastases and no other healthy tissues. This unique and spectacular specificity was already exploited to attempt to cure OS. We have use these molecules to construct 2 CAR molecules, OSCAR-1 and OSCAR-3. We have expressed these OSCAR into human T cells, and have shown that T cells armed with OSCAR acquired the ability to get stimulated by OS cell lines and kill them. We now know that these effects are specific and highly efficient. We have completed an animal study to test the efficiency of these OSACR T cells when injected in vivo. Here, mice were engrafted with a human OS cancer cell lines, and treated with OSCAR T cells or T cells alone. We observed that only the group treated with OSCAR was cured, suggesting that OSCAR T cells could be eligible for a clinical use. The target of TP-1 and TP-3 was not clearly identified. During the course of this project we outsourced this analysis isolated the target. This will open a path for further studies on the biology of OS development and the understanding of biomarkers in OS. We validated this target by bioinformatic analysis which supports that the target is highly present in OS biopsies, in particular in lung metastases. We have also performed some cell biology analysis and molecular manipulations to confirm this target. Finally, in order to further develop OSCAR-1 and OSCAR.3 for clinical use, we have performed safety experiments where healthy tissues were tested as target for OSCAR Tc and detected no cross-recognition suggesting that these molecules are safe. This grant has also covered the manufacturing of GMP mRNA material for clinical testing. From this work we concluded that the OSCAR technology has a great potential to become an efficient treatment for patients with OS lung metastases.

- We have isolated two potential therapeutic molecules to treat OS - We have prepared GMP grade material to treat 5 patients - We have established a clinical team - We have filled 2 patent families - We have attracted interest from pharmaceutical companies (2) and a research foundation

The present application focuses on the development of two CARs targeted against osteosarcoma (OS). Two monoclonal antibodies which are highly specific for OS have been developed and target two unique epitopes on a unique cell-surface marker of OS. Their specificity for OS spares normal tissue reactivity, mainly restricted to proliferating osteoblasts. They have been well-characterized immunohistochemically on a large series of fresh OS-tumor samples. We have designed CARs based on these two targets and have evaluated them in vitro. Our data demonstrates that these molecules have the potential to become game changers for the treatment of OS. We herein apply for support to the final steps of pre-clinical studies and the commercial development of these unique CARs.