Rituxan (rituximab) is a cancer medication in a class of medications called biologic antineoplastic agents. It interferes with the growth and spread of cancer cells. It is a man-made protein designed to act just like the antibodies produced by our immune system, by seeking out a specific protein on a cell and attaching to it. Rituxan finds a protein on normal and cancerous B-cells called CD20 and attaches to it, allowing the working parts of the immune system to find and destroy the malignant B-cells. Some lymphomas and leukemias in which there are too many B cells, overactive B cells, or dysfunctional B cells may be treated with Rituxan.

Rituxan is used in combination with other cancer medications to treat non-Hodgkin's lymphoma or chronic lymphocytic leukemia. The medication may also be used with other medications to treat the symptoms of rheumatoid arthritis, Wegener's Granulomatosis, and Microscopic Polyangiitis. 

Rituxan may also be prescribed for other uses not listed here, including the management of kidney transplant recipients.