Rituxan is a therapeutic antibody that binds to a particular protein -- the CD20 antigen -- on the surface of normal and malignant B-cells. It then recruits the body's natural defenses to attack and kill the marked B-cells. Stem cells (B-cell progenitors) in bone marrow lack the CD20 antigen, allowing healthy B-cells to regenerate after treatment and return to normal levels within several months.

Rituxan is indicated as a single-agent treatment for relapsed or refractory low-grade or follicular, CD20-positive, B-cell NHL. More than 300,000 patients have been treated with Rituxan worldwide since approval. Genentech and Biogen Idec co-market Rituxan in the United States. Roche markets Rituxan in the rest of the world, except Japan, where Rituxan is co-marketed by Roche, Chugai and Zenyaku Kogyo Co. Ltd.