B-lymphocyte antigen CD19, B-lymphocyte antigen CD20, and T-cell surface glycoprotein CD3 epsilon complex (CD19-CD3 and CD20-CD3)

The CD19–CD3 and CD20–CD3 protein–protein interfaces are the structural contact regions formed when multispecific therapeutic agents, such as bispecific T-cell engagers (BiTEs) or bispecific antibodies (BsAbs), simultaneously bind to B-cell surface antigens and the T-cell receptor complex (Labrijn et al., 2019, Nature Reviews Drug Discovery). CD19 and CD20 are well-characterized biomarkers for B-lymphocytes and are highly expressed in various hematologic malignancies, including B-cell acute lymphoblastic leukemia and non-Hodgkin lymphoma (UniProt P15391, P11836). CD3, specifically the epsilon subunit (CD3e), is a key signaling component of the T-cell receptor complex (UniProt P07766). By physically bridging a cytotoxic T-cell to a target B-cell, these drugs create a synthetic immunological synapse at these interfaces, bypassing the requirement for MHC-restricted antigen presentation. This interaction triggers T-cell activation, leading to the release of perforin and granzymes that induce rapid apoptosis of the malignant B-cell. Clinically approved drugs targeting these interfaces, such as blinatumomab (CD19-CD3) and mosunetuzumab (CD20-CD3), have demonstrated significant efficacy in relapsed or refractory settings, though they require careful management of immune-mediated toxicities like cytokine release syndrome (FDA Label: Blincyto, Lunsumio).

Other names

CD19xCD3CD20xCD3CD19/CD20/CD3 trispecificB-cell T-cell engager interfacesBiTE targetsBispecific antibody interfaces

T-cell redirection via bispecific or multispecific antibody binding, which facilitates the formation of an artificial immunological synapse between a cytotoxic T-cell (via CD3 epsilon) and a target B-cell (via CD19 or CD20), leading to MHC-independent T-cell activation and granzyme/perforin-mediated B-cell lysis.