According to results recently presented at the 47th annual meeting of the American Society of Clinical Oncology (ASH), the targeted agent HuMax®-CD20, which is still in clinical trials, provides anticancer activity in patients with chronic lymphocytic leukemia (CLL) who have stopped responding to Rituxan® (rituximab).

CLL is a cancer involving the lymph (immune) system; this includes lymph nodes, blood and blood vessels throughout the body, spleen, thymus, and tonsils. High quantities of this cancer are present throughout circulating blood and in bone marrow (spongy material inside large bones that produces blood-forming cells).

CLL 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, accumulating 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.

CLL is typically considered a slow-growing or low-grade cancer. Treatment for CLL often includes the targeted agent Rituxan; Rituxan is a monoclonal antibody, which is a protein developed in a laboratory. It is targeted against the antigen (protein) called CD-20 that is found on the surface of B-cells. The binding action stimulates of the immune system to kill the cell to which Rituxan is bound. It also triggers pathways involved in direct cellular death.

Since Rituxan is a targeted therapy, it is typically very well tolerated. This is particularly attractive for elderly patients or patients who have other medical conditions that make them ineligible for chemotherapy.

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HuMax-CD20 is a monoclonal antibody that is also targeted against the CD20 antigen. However, HuMax-CD20 uses different mechanisms to kill cancer than Rituxan; direct killing of the cells does not appear to occur with HuMax-CD20.

Researchers from several European medical centers recently conducted a clinical trial further evaluating HuMax-CD20 in patients with CLL. This trial included 33 patients who had stopped responding to standard therapies. Patients had received a median of five prior treatments with Rituxan. Early results were recently presented.

  • Nearly half of the patients experienced an anticancer response with HuMax-CD20 (46%).
  • The average reduction of cancerous cells in the bone marrow was from 80% to 40%.
  • HuMax-CD20 was tolerable in all patients.

The researchers concluded that HuMax-CD20 appears to be a promising new agent in the treatment of CLL that has stopped responding to Rituxan. Future trials will further evaluate HuMax-CD20 in patients with CLL.

Patients with CLL who have stopped responding to Rituxan or standard therapies may wish to speak with their physician regarding their individual risks and benefits of participation in a clinical trial further evaluating HuMax-CD20 or other promising new therapeutic agents. Two sources of information regarding ongoing clinical trials include the National Cancer Institute (www.cancer.gov) and www.cancerconsultants.com.

Reference: Coiffier B, Tilly H, Pedersen L, et al. HuMax CD20 fully human monoclonal antibody in chronic lymphocytic leukemia: early results from an ongoing phase I/II clinical trial. Blood. 2005;106:135a, abstract number 448.

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