Researchers from the MD Anderson Cancer Center have reported that the combination of Rituxan® (rituximab) and granulocyte macrophage-colony stimulating factor (Leukine®, sargramostim) is well tolerated and very effective in the treatment of chronic lymphocytic leukemia (CLL). The results of this phase II clinical trial were presented at the 47th annual meeting of the American Society of Hematology in December, 2005.
Chronic lymphocytic leukemia is the most common form of adult leukemia. The American Cancer Society estimates that approximately 8,000 people will be diagnosed with CLL this year. Currently, there are approximately 60,000 people in the U.S. living with CLL.
CLL is characterized by the production of atypical lymphocytes. Lymphocytes are specialized immune cells that exist in two forms: B- and T-cells. These cells are produced in the bone marrow and each serves a specific function in fighting infection.
The large majority of CLL cases involve mature B-lymphocytes that tend to live much longer than normal. B-lymphocytes accumulate in the blood, bone marrow, lymph nodes, and spleen. This results in overcrowding of these areas and suppression of the formation and function of blood and immune cells. Additionally, the cancerous lymphocytes themselves do not function normally, leading to a further decrease in the body’s ability to fight infection.
Rituxan is a monoclonal antibody that has been designed to recognize and bind to a part of B-cells known as the CD20 antigen. The binding of Rituxan stimulates the immune system to attack the B-cells; other properties of Rituxan are speculated to be involved in the direct killing or disabling of the B-cell.
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Leukine enhances the expression of the CD20 antigen on B-cells. Enhanced expression of CD20 may increase the ability of Rituxan to bind to and kill cancerous B-cells.
To evaluate the combination of Rituxan and Leukine in the treatment of CLL, researchers conducted a phase II clinical trial among 85 patients with CLL. The study included three groups of patients: patients with previously untreated CLL and Rai stage 0-II (low- or intermediate-risk CLL); previously untreated patients over the age of 70 years; and previously treated patients with evidence of active disease.
- Among the patients over the age of 70, 86% experienced at least a partial reduction in detectable CLL following treatment, and 50% experienced a complete disappearance of detectable CLL.
- Among the patients with Rai stage 0-II, 80% experienced at least a partial reduction in detectable CLL following treatment, and 40% experienced a complete disappearance of detectable CLL.
- Among patients with previously treated, active CLL, 47% experienced at least a partial reduction in detectable CLL, and 17% experienced a complete disappearance of detectable CLL.
The researchers conclude that the combination of Rituxan and Leukine for the treatment of CLL “is well tolerated and associated with an encouragingly high response rate.”
Reference: Ferrajoli A, O’Brien SM, Faderl SH et al. Rituximab plus GM-CSF for Patients with Chronic Lymphocytic Leukemia. Blood. 2005;106:214a, abstract number 721.
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