rituximab

Rituximab is a chimeric monoclonal antibody that binds CD20, a surface antigen on mature B cells. Binding leads to B-cell depletion through antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity, and induction of apoptosis. It is not active against stem cells or plasma cells and does not directly affect T cells.

Rituximab is used to treat certain B-cell malignancies, including CD20-positive non-Hodgkin lymphomas and chronic lymphocytic leukemia, typically as part of combination regimens or as monotherapy in selected settings. It is also approved for autoimmune diseases such as rheumatoid arthritis, granulomatosis with polyangiitis, and microscopic polyangiitis, where it reduces B-cell–mediated autoimmunity and inflammatory activity.

Administration is by intravenous infusion, with dosing and schedule varying by indication. Premedication with acetaminophen and an antihistamine is common to reduce infusion reactions; corticosteroids may be used in some regimens. Infusion reactions are most common with the first dose and may require slowing or stopping the infusion.

Safety concerns include infusion reactions, infections (including hepatitis B reactivation and opportunistic infections), neutropenia, and hypogammaglobulinemia. A rare but serious risk is progressive multifocal leukoencephalopathy. Use in pregnancy is cautioned; live vaccines should be avoided during treatment, and vaccination status should be reviewed prior to therapy.

Rituximab was first approved in 1997 for CD20-positive non-Hodgkin lymphoma and has since obtained additional indications. It is available in multiple markets as rituximab products, including biosimilars, which provide alternatives to the original monoclonal antibody.