Rituximab is a monoclonal antibody that targets CD20-positive B cells, used off-label for systemic lupus erythematosus (SLE), particularly in refractory cases or when there is involvement of the kidneys, central nervous system, or blood cells.

Though not FDA-approved for SLE, it is often used when patients fail standard treatments like corticosteroids, mycophenolate, or azathioprine. Rituximab may be especially helpful in lupus nephritis and autoimmune cytopenias. It is administered as an IV infusion, typically in 2 doses spaced 2 weeks apart, and repeated as needed. Potential side effects include infusion reactions and increased risk of infection, including reactivation of hepatitis B.