Definition

An engineered immunoglobulin M (IgM) bispecific antibody, with potential antineoplastic activity. Anti-CD20/CD3 bispecific IgM antibody IGM2323 contains ten high affinity binding domains for the tumor-associated antigen (TAA) CD20, and one binding domain for CD3, a T-cell surface antigen. Upon administration, IGM2323 binds to both T cells and CD20-expressing B-lineage tumor cells. The resulting cross-linkage may trigger a potent cytotoxic T-lymphocyte (CTL) response against the CD20-expressing tumor B cells. Additionally, IGM-2323 induces complement-dependent cytotoxicity (CDC) to a greater extent than anti-CD20/anti-CD3 IgG bispecific antibodies, thereby further enhancing the killing CD20-expressing tumor cells. The extra binding units of IGM-2323 may bind cancer cells that express relatively low amounts of CD20. Also, compared to IgG format bispecific T-cell engaging antibodies, IGM2323 appears to induce less cytokine release, which may reduce the risk of cytokine release syndrome (CRS). CD20 is exclusively expressed on B-cells during most stages of B cell development and is often overexpressed in B-cell malignancies.