A drug used alone or with other drugs to treat certain types of chronic lymphocytic leukemia and B-cell non-Hodgkin lymphoma that are CD20 positive. It is also being studied in the treatment of other conditions and types of cancer. Rituxan binds to a protein called CD20, which is found on B cells and some types of cancer cells. This may help the immune system kill cancer cells. Rituxan contains the active ingredient rituximab. It is a type of monoclonal antibody.