Cord blood-derived natural killer cells engineered with a novel, highaffinity chimeric antigen receptor can eliminate acute myeloid leukemia cells with minimal C-type lectin-like molecule-1 expression

CAR NK cell therapy is expected to be developed to treat acute myeloid leukemia (AML). C-type lectin-like molecule 1 (CLL-1) is a candidate target. However, AML cells with minimal CLL-1 expression (CLL-1dim) may not be eliminated by CAR NK cells. Here we demonstrate that cord blood (CB)-derived NK cells transduced with a novel high-affinity CAR that recognizes CLL-1 can eliminate CLL-1dim AML cells. A newly established anti- CLL-1 monoclonal antibody (mAb) designated as 2-23 exhibits a higher affinity for CLL- 1 than the widely used anti-CLL-1 mAb M26. CB-derived NK cells transduced with a CAR derived from 2-23, but not M26, killed CLL-1dim AML cells in vitro. Additionally, treatment with 2-23 CAR NK cells, but not M26 CAR NK cells, significantly enhanced the survival of the mice transplanted with CLL-1dim AML cells in vivo. Furthermore, in AML patient-derived xenograft models, the 2-23 CAR NK cells expanded robustly, persisted, and eradicated AML cells.