CD20 antigen (Rituximab target) (CD20)

The actual therapeutic target for rituximab is the CD20 antigen, a transmembrane phosphoprotein expressed primarily on the surface of normal and malignant pre-B and mature B lymphocytes. It plays a role in regulating cell cycle progression during human B-cell activation. Although its precise physiological function remains incompletely understood, it appears involved in calcium influx necessary for cell activation. Targeting this molecule with monoclonal antibodies such as rituximab leads to selective depletion of circulating and tissue-based CD20-positive B-cells via multiple mechanisms—complement-mediated lysis, antibody-dependent cellular cytotoxicity by immune effector recruitment, direct induction of apoptosis through intracellular signaling disruption—and results in clinical benefit across various cancers involving abnormal or excessive proliferation/activation of these lymphocytes as well as autoimmune disorders where pathogenic autoantibody-producing clones are present. The safety profile reflects both its efficacy at depleting pathological clones but also risks associated with broad suppression/depletion of normal humoral immunity.

Other names

B-lymphocyte antigen CD20MS4A1Bp35Leukocyte surface antigen Leu-16

Drugs targeting CD20 act by: - Binding to the CD20 antigen on B cells - Inducing complement-dependent cytotoxicity (CDC), leading to cell lysis - Triggering antibody-dependent cellular cytotoxicity (ADCC), recruiting immune effector cells to destroy targeted B cells - Inducing direct apoptosis of targeted B cells through signaling changes in calcium flux and mitochondrial pathways