 Rituximab is a type of drug known as a monoclonal antibody. It is designed to act against the cluster of differentiation antigen 20 CD20 antigen that is found on the surface of both normal B lymphocytes or on the malignant lymphoma cells. When rituximab attacks the CD20 antigen, it can kill the lymphoma cells. lenalidomide is known as an immunomodulatory drug. It is thought to work by helping the immune system fight disease. 