CD19 x CD3

Class

T-cell engaging bispecific antibody (T-cell engager, TCE)

Pathway

Bridges CD19+ B cells with CD3+ T cells to drive T-cell-mediated B-cell killing/depletion

CD19 is a surface protein expressed on B cells across most stages of their development, from early precursors through mature forms, and it remains present on the majority of B-cell cancers, including many leukemias and lymphomas. CD3 is a signaling component of the T-cell receptor complex, found on nearly all T cells. A CD19 x CD3 bispecific antibody carries two distinct binding arms: one grips CD19 on a B cell, the other grips CD3 on a T cell. By binding both simultaneously, the molecule physically links the two cells together, forming an artificial immune synapse without requiring the T cell to recognize its usual antigen target. This forced contact activates the T cell, which then releases cytotoxic proteins that kill the attached B cell. Because activation does not depend on the T cell's native receptor specificity, this approach can recruit a broad portion of a patient's existing T-cell population against B cells bearing CD19, rather than relying on tumor-specific immune recognition developing naturally. This mechanism is relevant across B-cell malignancies and has also been explored in autoimmune conditions where depleting CD19-positive B cells, including those producing harmful autoantibodies, may reduce disease activity.