Trending topics and news in HCT and Cellular Therapy

Off-the-shelf Dual CAR-iNKT Cell Immunotherapy Eradicates Medullary and Leptomeningeal High-risk KMT2A-rearranged Leukemia

Researchers at Imperial College London and the University of Oxford have found a bispecific CD19 and CD133 chimeric antigen receptor (CAR) engineered into invariant natural killer T cells can eradicate high-risk KMT2A rearranged acute lymphoblastic leukemia (ALL) in vivo, including difficult meningeal disease, with curative survival in multiple xenograft models. Published in Blood, the study shows that combining two leukemia antigens in a single CAR and deploying it in an iNKT cell platform can overcome antigen heterogeneity and deliver deeper remissions than monospecific CAR approaches.

KMT2A rearranged ALL, particularly in infants, has aggressive biology and a high propensity for relapse and extramedullary spread, and current CAR T strategies can be limited by antigen escape, sanctuary sites such as the CNS, and variable antigen density. The authors therefore designed a bispecific CAR targeting CD19 and the stem-like marker CD133 and expressed it in iNKT cells, which have innate-like cytotoxic features and distinct trafficking properties. They tested activity in several mouse models, including an aggressive SEM leukemia model with medullary, splenic, hepatic, and leptomeningeal involvement, and then extended the approach to a primary CRISPR-engineered KMT2A::AFF1 model and a patient-derived xenograft, using tumor burden monitoring, histology of brain meninges, and flow cytometry of marrow and spleen to assess clearance.

In the SEM leukemia model, treatment with 5×10⁶ bispecific CAR iNKT cells on day 6 (about 2% marrow leukemia) or 1×10⁷ cells on day 12 (about 15% marrow leukemia) eliminated detectable disease by bioluminescence and resulted in 100% long-term survival. Untreated mice developed heavy meningeal infiltration, exceeding grade 3 out of 5, whereas treated animals had no detectable meningeal leukemia. In the primary CRISPRKMT2A::AFF1 model, CD133 was present on about 65% of CD19+ blasts, and treatment at first engraftment with 5×10⁶ bispecific CAR iNKT cells yielded 100% survival beyond 60 days with no detectable HLA class I positive leukemia in marrow or spleen (P < .0001). A KMT2A::AFF1 patient-derived xenograft treated with 5×10⁶ cells on day 15 showed no detectable human cells at days 33 and 45. Mechanistically, iNKT cytotoxicity depended strongly on NKG2D, with NKG2D upregulated to nearly 100% after leukemia exposure and antibody blockade causing a concentration dependent reduction in killing. These findings are important because they support a practical route to reduce relapse and CNS failure in high risk ALL by pairing bispecific antigen coverage with an effector cell type that can deliver potent, multi receptor mediated cytotoxicity.

Reference:

Ren H, Elliott N, Lye B, et al. Off-the-shelf dual CAR-iNKT cell immunotherapy eradicates medullary and leptomeningeal high-risk KMT2A-rearranged leukemia. Blood. 2026;147(2):180-196.

http://doi.org/10.1182/blood.2025029302