A Glycoengineered Anti-ROR1 Antibody, GE-zilovertamab, Selectively Enhances Antibody-Dependent Cellular Cytotoxicity Against Chronic Lymphocytic Leukemia

Background 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). Methods 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 (PBMC) effectors. Treatments included the anti-CD20 mAb rituximab, anti-ROR1 mAbs (GE-zilovertamab, zilovertamab), and the endocytosis inhibitor prochlorperazine, and ADCC was quantified. Results GE-zilovertamab showed significantly higher ADCC versus its parental antibody that was comparable to that of rituximab. We find that the endocytosis inhibitor prochlorperazine further increased this effect. Conclusions 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.