A drug used alone or with other drugs to treat certain types of B-cell non-Hodgkin lymphoma that are CD20 positive. It is used under the brand names Truxima and Rituxan to treat these cancers. Rituximab is also used under the brand name Rituxan to treat chronic lymphocytic leukemia that is CD20 positive. It is also being studied in the treatment of other conditions and types of cancer. Rituximab 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. Rituximab is a type of monoclonal antibody.