A glycoengineered anti-ROR1 antibody, GE-zilovertamab, selectively enhances antibody-dependent cellular cytotoxicity against chronic lymphocytic leukemia

Abstract Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is selectively expressed on chronic lymphocytic leukemia (CLL) B cells and certain cancers, but is absent from normal B cells and healthy adult tissues. GE-zilovertamab, an afucosylated anti-ROR1 IgG1 antibody, is engineered to increase FcγRIIIA binding and thereby enhance antibody-dependent cellular cytotoxicity (ADCC). Co-culture assays were performed using CLL cell lines (MEC1, MEC1-ROR1) and primary CLL cells with Jurkat-Lucia™ NFAT-CD16, NK, or peripheral blood mononuclear cell effectors. Treatments included the anti-CD20 mAb rituximab, anti-ROR1 mAbs (GE-zilovertamab, zilovertamab), and the endocytosis inhibitor prochlorperazine, and ADCC was quantified. GE-zilovertamab showed significantly higher ADCC than its parental antibody and activity that was comparable to that of rituximab. We find that the endocytosis inhibitor prochlorperazine further increased this effect. GE-zilovertamab is a promising next-generation immunotherapeutic for CLL, combining selective targeting of ROR1 with the potential to reduce therapy-induced immunodeficiency compared with anti-CD20 antibodies. Statement of Significance An afucosylated anti-receptor tyrosine kinase-like orphan receptor 1 antibody potently kills receptor tyrosine kinase-like orphan receptor 1-expressing leukemic B cells while sparing normal B cells, and this selective cytotoxicity is further enhanced by prochlorperazine. This combination has the potential to advance leukemia immunotherapy by targeting malignant cells while preserving humoral immunity, thereby addressing infection risks associated with anti-CD20 antibody regimens.