Off-the-shelf dual CAR-iNKT cell immunotherapy eradicates medullary and leptomeningeal high-risk KMT2A-rearranged leukemia.
Ren H., Elliott N., Lye B., Sharif Shohan MU., Cross JW., Field L., Ponnusamy K., Rice S., Jackson T., Leontari I., El Ouazzani N., Thomas R., Inglott S., Bartram J., Smith O., Bond J., Roberts IAG., Halsey C., Bashford-Rogers R., Milne TA., Roy A., Karadimitris A.
Current therapies, including autologous chimeric antigen receptor (CAR) T-cell immunotherapy, fail to cure half of infants with KMT2A-rearranged acute lymphoblastic leukemia (KMT2Ar-ALL), a disease characterized by frequent central nervous system involvement, poor treatment response, early relapse, and lineage switching. More effective treatment strategies, including the availability of off-the-shelf immunotherapies, is particularly relevant in infants. PROM1/CD133 is a direct target of KMT2A-fusion oncoproteins and is expressed on leukemic cells. Allogeneic invariant natural killer T (iNKT) cells, "innately" more powerful effectors than T cells, can be deployed off-the-shelf without risk of acute graft-versus-host disease. Here, we equip iNKT cells with CD19- and/or CD133-targeting CARs, and investigate their antileukemia activity against KMT2Ar-ALL in relevant in vitro and in vivo models. Compared with monospecific counterparts and dual, bispecific CAR T cells, bispecific CD19-CD133 CAR-iNKT cells have a more potent antileukemia activity, effectively targeting both CAR antigen-high and -low leukemia. Bispecific CAR-iNKT cells eradicate medullary and, notably, leptomeningeal leukemia, and induce sustained remissions without discernible hematologic toxicity. Mechanistically, the more potent antileukemia effect of CAR-iNKT cells over CAR T cells is mediated by a pronounced CAR-dependent and CAR antigen-dependent upregulation of the innate activating receptor NKG2D on CAR-iNKT cells, and its engagement by its corresponding ligands on KMT2Ar-ALL cells. This ensures effective leukemia targeting even with downregulation of CD133 or CD19. Thus, by engaging with 2 different types of leukemia-associated antigens, that is, CAR antigens and NKG2D ligands, CAR-iNKT cells provide a powerful platform for the treatment of KMT2Ar-ALL. This approach can be readily adapted for other high-risk malignancies, including those with otherwise difficult to target leptomeningeal involvement.