Targeting Leukemic Stem Cell Expressing IL-1RAP Protein (Interleukin-1 receptor accessory Protein) : Anti-tumor immunotherapy approach using genetically modified T cells (CAR)

Nous avons produit des CART-cells et des LT-mock ont été produits ex-vivo. L'efficacité de transduction est mesuré par l'expression CD3+/CD19+ (82% en moyenne, n=S), en cytométrie en flux. L'expression protéique de CAR a été vérifiée par western blot et en cytométrie en flux attestant de son expression membranaire. Nous avons testé la fonctionnalité de la cassette suicide iCaspase9/ AP1903 sur CART-cells après 48h de traitement à I' AP1903. Nous avons montré que plus de 90% des CART-cells entrent en apoptose (Marquage 7-AAD en cytométrie en flux). Nous avons ensuite réalisé des tests fonctionnels in-vitro des CART-cells contre des lignées LMC exprimant naturellement IL-lRAP ou contre des lignées transfectées pour exprimer la forme membranaire d'IL-lRAP. Après co­culture des CART-cells en présence des cellules cibles IL-lRAP+ nous avons montré qu'ils prolifèrent (test CFSE), qu'ils sécrètent de l'interféron y et des cytokines inflammatoires. Enfin, par marquage 7-AAD, nous avons démontré la cytotoxicité des CART-cells contre les cellules ILl-RAP+. Finalement, nous avons montré l'efficacité des CART-cells in vivo, dans un modèle de xénogreffe tumorales dans des souris immunodéficiences NSG greffées par la lignée K562-IL1RAP+ / Luciférase +. On constate une diminution de la masse tumorale 4 jours après injection des CART-cells, jusqu'à disparition totale. Cette preuve de concept laisse entrevoir des perspectives thérapeutiques alternatives dans le traitement de la LMC ou LAM, qui devront être optimiser dans des modèles murins (séquence et nombres d'injection, nombres de cellules, associations avec ITKS ou autres chimiothérapies) afin de conduire un essai clinique de phase I, pour démontrer la faisabilité et la sécurité de l'approche pour envisager une démonstration d'efficacité chez l'homme. La sécurisation par la cassette suicide permet d'envisager l'utilisation des CART-cells en situation autologue ou allogénique (Donor Lymphocytes infusion, DU)Chronic myeloid leukemia (CML) is a myeloproliferative disorder and is characterized by the presence of a Philadelphia chromosome (Phl) encoding the BCR-ABL fusion protein with constitutive tyrosine kinase activity. The treatment by Tyrosine Kinase lnhibitors (ITK) is not curative. The problem today is ta target leukemic stem cells (HSCs) to prevent relapse of patients after stopping treatment with TKI and permanently eradicate the disease. Studies have identified the interleukin-1 accessory protein receptor (IL-lRAP) as a potential target for killing CSL (BCR-ABL1 positive) in CML or in acute myeloid leukemia (AML). We therefore propose to develop a cell therapy approach targeting IL-lRAP, using T cells (LT) redirected by a CAR (Chimeric Antigen Receptor) in the treatment of CML and AML. We produced a specific anti-lL-1RAP murine monoclonal antibody (mAb) called # A3C3. We tested the specificity of the antibody # A3C3 in flow cytometry, in Western blot, by immunohistochemistry or confocal microcopy, on positive human cell lines IL-1RAP (KU812) or IL-1RAP negative (Raji). Moreover, by using this antibody, we have demonstrated by immunohistochemistry, on 20 different normal tissues that our antibody does not recognize or very few non-specific (off-target) targets. Finally, we demonstrated that this antibody is able to detect positive IL-1RAP CSLs in primary bone marrow or peripheral blood samples of LMC patients at diagnosis or after ITK treatment. By molecular biology, we have sequenced and identified rearrangements of the heavy (lgH) and light {lgL) chains coding region for hypervariable regions of# A3C3. The coding sequence for the "single chain variable fragment" (scFv), lin king the 2 lgH and lgl chains, was cloned into a 3rd generation lentiviral skeleton securised by a suicide gene, inducible caspase 9 (iCASP9). We produced CART-cells and LT-mock ex-vivo. The transduction efficiency is measured by CD3 + / CD19 + expression (82% on average, n = 5), in flow cytometry. The functionality of the suicide cassette iCaspase9/AP1903 on CART-cells after 48h treatment with AP1903 was tested. We have shown the death of more than 90% of CART-cells (7-AAD labeling in flow cytometry). We then performed in-vitro functional tests of CART-cells against LMC lines naturally expressing IL-1RAP or against transfected lines to express the membrane form of IL-1RAP. After co-culture of CART-cells in the presence of IL-1RAP + target cells, we have shown that they proliferate (CFSE test), that they secrete interferon y and inflammatory cytokines (intracellular labeling and Cytokines Bead Array assay). They are able to degranulate (CD107a & b labeling). Finally, by 7 AAD labeling, we demonstrated the cytotoxicity of CART-cells against IL1-RAP + cells. Finally, we showed the effectiveness of CART-cells in vivo, in a tumor xenograft model in NSG immunodeficiency mice engrafted by the K562-IL1RAP+/Luciferase+ line. There is a decrease in the tumor load 4 days after injection of CART-cells, until complete disappearance.This proof of concept suggests alternative therapeutic perspectives in the treatment of CML or AML, which should be optimized in murine models (sequence and injection numbers, cell numbers, associations with ITKS or other chemotherapies) in order to Phase I clinical trial, to demonstrate the feasibility and safety of the approach to consider a demonstration of efficacy in human. Securing by the suicide cassette makes it possible to consider the use of CART-cells in an autologous or allogeneic situation (Donor Lymphocytes infusion, DU