Rituxan, also known as rituximab, is a drug that is used in the treatment of certain types of cancer and autoimmune diseases. This drug is a monoclonal antibody, which means it targets specific cells in the body. 

Rituxan is approved for use in the treatment of non-Hodgkin’s lymphoma (NHL), chronic lymphocytic leukemia (CLL), rheumatoid arthritis (RA), and granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA), which are types of vasculitis.

Antibodies are an integral part of the body’s immune system.  Normally, the body creates antibodies in response to an antigen, such as a protein in a germ, that has entered the body. The antibodies attach to the antigen in order to mark it for destruction by the immune system. 

When given to the patient, these monoclonal antibodies will attach to matching antigens like a key fits a lock. Since monoclonal antibodies target only specific cells, they may cause less toxicity to healthy cells. 

Rituxan works by targeting the CD20 antigen on normal cells and B-cells, then the body’s natural immune defenses are recruited to attack and kill the marked B-cells.  

In NHL and CLL, B-cells can become cancerous and multiply uncontrollably. By destroying these cancerous B-cells, Rituxan can help to slow or stop the progression of the disease. 

In RA and vasculitis, B-cells play a role in the autoimmune response that causes inflammation and tissue damage. By targeting and destroying these B-cells, Rituxan can help to reduce inflammation and slow the progression of these diseases.

Stem cells (young cells in the bone marrow that will develop into the various types of cells) do not have the CD20 antigen. This allows healthy B-cells to regenerate after treatment.