Rituximab (Rituxan) has been cleared for marketing by the FDA. Previously known as the C2B8 antibody, rituximab(Drug information on rituximab), is a single-agent monoclonal antibody therapy for relapsed or refractory, low-grade or follicular, CD20-positive, B-cell non-Hodgkins lymphoma, rituximab is the first new single-agent therapy for non-Hodgkins lymphoma in 10 years and the first licensed for the treatment of cancer in the United States.
In the ongoing pivotal trial being conducted in 31 US sites, rituximab, when used alone, produced a 48% overall response rate, and 80 of 166 patients experienced tumor shrinkage of 50% or more following four weekly infusions. The median duration of response is projected to be 10 to 12 months. These preliminary results corroborated those seen in earlier studies.
In clinical trials, the most common adverse events associated with rituximab were infusion-related, consisting mainly of mild to moderate flu-like symptoms (eg, fevers, chills, rigors), which occurred in the majority of patients during the first infusion. Other events that occurred with less frequency included nausea, rashes, fatigue, and headache.
More serious events included hypotension, wheezing, sensation of tongue or throat swelling, and recurrence of cardiac events in patients with a history of angina or arrhythmia. These symptoms were usually limited in duration to the period of infusion and decreased with subsequent infusions.
Turning Point in Lymphoma Treatment
Rituxan presents an important turning point in the treatment of lymphoma, said Myron Czuczman, MD, assistant professor of medicine, Roswell Park Cancer Institute, Buffalo, New York, and a key investigator. Although it is not a cure, we finally have a cancer agent that can be effective with less serious side effects than with conventional chemotherapy. Treatment can also be completed in 22 days, unlike the typical 4- to 6-month chemotherapy regimen. This is exciting news, especially for elderly patients and relapsed patients who have failed at least one standard treatment regimen.
There are approximately 250,000 patients in the United States with B-cell non-Hodgkins lymphomas, approximately one-half of whom have low-grade or follicular lymphoma. A portion of these patients will have multiple relapses and may be eligible for rituximab therapy. Currently, standard treatment for these patients consists of chemotherapy and/or radiotherapy.
Rituximab works by binding to a particular protein (the CD20 antigen) on the surface of mature B-cells and B-cell tumors and recruiting the bodys natural defenses to attack and kill both malignant and normal mature B-cells. Stem cells present in the bone marrow lack the CD20 antigen and, therefore, are not affected by the treatment. In clinical studies, B-cells returned to normal levels within several months after completion of treatment.