CAR T-cells for CD1-positive cancer

Diego Sanchéz, Heleia Roca, Francisco Gutiérrez, Clara Bueno, Pablo Menéndez
Josep Carreras Leukemi Research Institution

The choice of the antigen against which we wish to re-direct T-cells represents a major advance to solve the problems associated with the shared expression of T-cell markers between normal and malignant T-cells. We identified that CD1a, a lipid-presenting molecule, is a suitable target for 5 treating a large subset of T-ALL, i.e. cortical T-ALL. We developed and functionally characterized CD1a-specific CARTs, which displayed robust cytotoxicity against T-ALL cell lines and primary cortical CD1a+ T-ALL cells both in vitro and in vivo in xenograft models. The CD1a CARTs continuously expanded 200-fold, similar to MOCK T-10 cells, demonstrating that redirecting CARTs against CD1a antigen does not induce T-cell fratricide. Also, the use of CD1a CARTs for cortical T-ALL bypasses the need for sophisticatedgenome editingbased disruption of target antigens in T-cells prior to CAR transduction as a strategy to avoid selfantigen-driven fratricide 15-17,19. We further demonstrated that in steady-state hematopoiesis, CD1a is exclusively expressed in a subset of cortical CD34+CD7+ thymic T progenitors, whereas earlier 15 CD34highCD7high T-progenitors lack CD1a. In addition, neither normal CD34+ HSPCs nor mature Tcells from multiple tissues express CD1a during ontogeny, thereby minimizing the risk of ontarget/off-tumor toxicity. Indeed, when human fetal thymus-derived CD7+ thymocytes were exposed to CD1a CARTs, only the CD1a+ cortical thymocytes were eliminated by the CD1a CARTs, while developmentally earlier and later thymic T-lineagepopulations (CD34+ and CD34-) were not targeted, 20 limiting the on-target/off-tumor effects to a developmentally transient thymic population of cortical thymocytes and further confirming thefratricide resistant nature of CD1a CARTs. The exclusive thymic localization of cortical thymocytes, and the fact that thymic subpopulations of CD34+CD7+CD1a- T-cell progenitors physiologically/constantly maturing into functional T cells25 reside upstream of CD1a+ cortical thymocytes, provides an additional level of safety for the use of CD1a CARTs in patients with R/R T-ALL. We do not expect irreversible toxicities or severe T-cell aplasia attributed to CD1a CARTs for the following reasons: i) the CD1a+ thymocyte population is a transient thymic T-cell fraction, eventually regenerated by upstream CD1a- T-cell progenitors; ii) CD1a CARTs themselves respond normally to viral antigens and therefore are likely to be protective 30 against pathogens; iii) the clinical use of specific antibodies against CD5 or CD7 42 did not reveal severe or irreversible toxicities; iv) there are multiple studies that demonstrate extrathymic maturation of T-cells and a balance between the innate and adaptive immune system that may, at least in part, guarantee immunological protection in patients who haveundergone partial or total thymectomy 45-47. 35 Thus, in one aspect, the present invention provides a chimeric antigen receptor (CAR) comprising an extracellular domain comprising a CD1a targeting-moiety, a transmembrane domain, and an intracellular signaling domain. The present invention also provides a nucleic acid encoding the CAR of the present invention. Further, 5 the present invention provides a cell comprising the nucleic acid and/or CAR of the present invention. And, the present invention provides a pharmaceutical composition comprising a plurality of cells in accordance with the present invention and a pharmaceutically acceptable carrier or diluent. The cell of the present invention or pharmaceutical composition of the present invention is provided 10 for use as a medicament. In particular, the present invention provides a method of treating a CD1apositive cancer comprising administering the cell of the present invention or the pharmaceutical composition of the present invention to a patient in need thereof.

Filing date: 14 Feb, 2019

EP19382104.8