uPAR-targeting CAR-NK cells enhance cytotoxicity against acute myeloid leukemia

Background: Relapsed/refractory acute myeloid leukemia (AML) remains difficult to treat, highlighting the need for new therapies. NK cell-based immunotherapy offers potent antitumor activity with low risk of GVHD or severe CRS. The urokinase plasminogen activator receptor (uPAR), encoded by PLAUR , is highly expressed on malignant and senescent cells while largely absent from healthy HSCs and most normal vital organs. We found PLAUR significantly upregulated in AML and confirmed strong uPAR surface expression on primary blasts. Based on this favorable profile, we developed an off-the-shelf uPAR-targeted CAR-NK platform with a CD28 costimulatory domain and secreted IL-15 to enhance persistence. Methods: Cord blood-derived NK cells were preactivated with IL-12/15/18 and transduced to express (i) uPAR-CAR, (ii) IL-15, or (iii) uPAR-CAR/IL-15. CAR expression, cytokine production, and phenotype were assessed by flow cytometry, ELISA, and CyTOF, respectively. Antileukemic activity against AML cell lines (MV4-11, THP-1, OCI-AML3) and primary blasts was tested by IncuCyte real-time killing and Annexin V staining. Long-term activity was assessed by sequential tumor rechallenge. In vivo efficacy was evaluated in NSG mice engrafted with luciferase-labeled OCI-AML3 and treated with a single NK infusion. Results: uPAR was highly expressed on AML blasts but minimal on healthy HSCs/HSPCs, confirming its suitability as a CAR-NK target. uPAR-CAR/IL-15 NK cells were efficiently generated, secreted IL-15, and expanded robustly. In vitro, they showed markedly enhanced and antigen-specific killing of all uPAR+ AML lines and primary blasts compared with CAR-only, IL-15-only, or non-transduced NK cells ( p < 0.0001), while PLAUR -knockout cells resisted killing. uPAR-CAR/IL-15 NK cells produced more IFN-gamma and TNF-alpha and maintained superior function during repeated tumor exposure, with CyTOF revealing an activation/cytotoxicity-enriched metacluster. In vivo, a single uPAR-CAR/IL-15 NK infusion significantly reduced leukemia burden, delayed progression, and improved NK persistence in bone marrow. Compared with non-transduced NKs, tumor burden in peripheral blood ( p < 0.05), bone marrow ( p = 0.001), and spleen ( p < 0.01) was substantially reduced, with no observed toxicity or weight loss. Taken together, uPAR is a safe, selective AML target. uPAR-CAR NK cells, particularly when armored with IL-15, display potent, antigen-specific, and durable antileukemic activity, supporting advancement of this platform for AML therapy.