rituksimab

Rituximab, marketed as Rituxan in the United States and MabThera elsewhere, is a chimeric monoclonal antibody that targets CD20, a surface protein on most mature B lymphocytes. It is used to treat CD20-positive B-cell malignancies such as non-Hodgkin lymphoma and chronic lymphocytic leukemia/small lymphocytic lymphoma, as well as several autoimmune diseases including rheumatoid arthritis, granulomatosis with polyangiitis, microscopic polyangiitis, and pemphigus vulgaris. In many indications it is given in combination with other therapies.

Rituximab binds CD20 and depletes B cells through mechanisms such as antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity, and apoptosis. It does not directly target plasma cells, so antibody levels may recover after treatment ends.

Administration is by intravenous infusion, with premedication to reduce infusion reactions. Dosing varies by disease: for various non-Hodgkin lymphomas, typical regimens involve 375 mg/m2 given once weekly for several weeks, often with chemotherapy; for CLL/SLL, regimens usually start with 375 mg/m2 and then 500 mg/m2 per cycle. In autoimmune diseases, schedules depend on the protocol and disease activity.

Common adverse effects include infusion reactions, fever, and nausea. Rituximab increases infection risk due to B-cell depletion and can reactivate hepatitis B; rare cases of progressive multifocal leukoencephalopathy have been reported. Long-term use may cause hypogammaglobulinemia. Vaccination responses may be reduced, and live vaccines are generally avoided during treatment.

Rituximab was approved by the U.S. FDA in 1997 for relapsed or refractory CD20-positive NHL and has since gained additional indications. Biosimilars are available in many markets.