LILRB1-directed CAR-T cells for the treatment of hematological malignancies.

CD19 CAR-T cells have established a new standard for relapsed/refractory B-cell malignancies. However, the treatment fails in 50% of patients, often due to CD19 antigen loss. Alternative immunotherapies targeting other antigens are being tested but show limited efficacy, especially in cases of lineage switching or loss of B-cell phenotype, highlighting the need for novel targets. Herein, we identified leukocyte-immunoglobulin-like-receptor-B1 (LILRB1, CD85j) as a novel target for CAR-T cells through cell surface proteomics on patient-derived samples of high-risk B-cell acute lymphoblastic leukemia (B-ALL). LILRB1, an immune inhibitory receptor, is normally expressed only on monocytes and B-cells. We observed stable LILRB1 expression in B-ALL and B-cell non-Hodgkin lymphoma (B-NHL), even after CD20/CD19-based immunotherapies. LILRB1 CAR-T cells showed antigen-specific antitumor activity in vitro against B-ALL/B-NHL cells, including those resistant to CD19 CAR-T-cells, and in vivo in B-ALL xenografts. Additionally, we identified LILRB1 in monocytic acute myeloid leukemia (AML) and demonstrated LILRB1 CAR-T cell cytotoxicity against AML cell lines in vitro and in vivo. These findings establish LILRB1 as a novel target for cancer immunotherapy and show evidence for the preclinical efficacy of LILRB1 CAR-T cells against haematological malignancies, including cases resistant to previous lines of immunotherapy, thus holding promise for further clinical development.