Off-the-shelf dual CAR-iNKT cell immunotherapy eradicates medullary and leptomeningeal high-risk KMT2A-rearranged leukemia
In a collaborative effort, researchers from the University of Oxford, Imperial College London, and Great Ormond Street Hospital have found that bi-specific CD19–CD133 CAR-invariant NKT cells eradicate both medullary and meningeal leukemia in KMT2A-rearranged acute lymphoblastic leukemia (ALL) models, producing deep and durable remissions. In SEM leukemia–bearing mice, a single infusion of 5×106 cells on day 6 or 107 cells on day 12 rapidly drove bioluminescence to baseline with 100 percent long-term survival. Brain histology confirmed clearance of meningeal disease, with infiltration scores falling from greater than 3 of 5 in controls to 0 of 5 following treatment. When meningeal leukemia was established prior to therapy, a day 16 dose eliminated CD19-positive cells by days 36 to 50 and prevented marrow and splenic relapse. The product also cleared primary KMT2A:AFF1 leukemia, including a patient-derived xenograft with low CD19 and CD133 expression, whereby treated mice yielded no detectable human cells at days 33 and 45.
Researchers compared the bi-specific CAR-iNKT to matched-donor CAR-T cells and found superior potency, with CAR-iNKT showcasing higher cytotoxicity and avidity across multiple KMT2A-rearranged lines and producinfg earlier, stronger effector outputs, including perforin, granzyme B, and interleukin 2 in vitro. In vivo, at a subtherapeutic 1×106 dose, CAR-iNKT reduced burden and extended survival more than CAR-T; at 5×106, CAR-iNKT drove leukemia to undetectable levels within 72 hours and achieved 100 percent leukemia-free survival, while CAR-T–treated mice relapsed. No acute graft-versus-host disease was observed, and mechanistically, CAR-iNKT upregulated the activating NK receptor NKG2D far more robustly than CAR-T following leukemia encounter.
Single-cell multiomic profiling of pre-infusion and post-infusion bone marrow CAR-iNKT revealed cytotoxic clusters enriched for perforin, granzymes, and NKG2D, together with oxidative phosphorylation and protein synthesis programs. By day 15 in leukemia-bearing mice, CAR-iNKT demonstrated heightened proliferation, recovery of interferon responses, and renewed NKG2D expression, with explanted cells weeks still expanding vigorously and retaining cytotoxicity. In a humanized cord blood model, bi-specific CAR-iNKT caused B-cell depletion but did not impair long-term hematopoiesis or CD34-positive progenitors, suggesting minimal off-tumor effects on stem cells. Overall, high-dose CD19–CD133 CAR-iNKT cells outperform CAR-T, eradicate leptomeningeal disease, and showcase off-the-shelf potential as a rapid bridge to transplant in aggressive KMT2A-rearranged ALL.
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. Published online September 3, 2025.