CD20 x CD3

Class

T-cell engaging bispecific antibody

Pathway

CD8/TCR-based T-cell engager bridging CD3+ T cells to CD20+ B cells for B-cell depletion

CD20 x CD3 bispecific antibodies are engineered to bind two different targets at once: CD20, a protein found on the surface of B lymphocytes (including malignant B cells in many lymphomas and leukemias), and CD3, part of the receptor complex present on nearly all T cells. By attaching to both cell types simultaneously, the antibody physically links a T cell to a B cell, creating a forced contact point called an immune synapse. This contact activates the T cell and triggers it to kill the attached B cell, regardless of what antigen that T cell would normally recognize. The biological rationale is to redirect a patient's existing T-cell population toward malignant or otherwise unwanted B cells without requiring prior immune priming against a tumor-specific antigen. This mechanism is broadly relevant in B-cell cancers, such as non-Hodgkin lymphomas and certain leukemias, where CD20 is consistently and stably expressed, and in some autoimmune diseases driven by pathogenic B cells. Compared with an antibody that targets CD20 alone, adding a CD3-binding arm converts B-cell elimination from a passive process, dependent on complement or natural killer cells, into an active, T-cell-driven killing mechanism that can operate even where those other effector systems are weak.