Return to Leukemia Health News

BL22 Immunotoxin Produces High Responses in Hairy Cell Leukemia

Results from an early-phase clinical trial evaluating an innovative form of treatment involving a toxin from bacteria has demonstrated high anti-cancer activity in patients with hairy cell leukemia, as recently reported in the New England Journal of Medicine. These results are consistent with results from preliminary trials evaluating BL22.

Hairy cell leukemia is a cancer that involves the blood and bone marrow. It is called hairy cell leukemia because these cancer cells have a "hairy" appearance when viewed under a microscope. This disease is characterized by the production of atypical B-lymphocytes, which are immune cells that are produced in the bone marrow (spongy material inside bones). B-lymphocytes have a specific function in aiding the body to fight infection. When hairy cell leukemia develops, the cancerous lymphocytes accumulate in the blood, bone marrow, lymph nodes and spleen. This results in overcrowding of these areas, suppressing the formation and function of blood cells and immune cells that are normally present, particularly in the bone marrow. Additionally, the cancerous lymphocytes themselves do not function normally, which leads to a further decrease in the ability of the body to fight infection. Standard treatment for hairy cell leukemia consists of chemotherapy, biological therapy (utilizing the body’s immune system to fight cancer) and/or high-dose chemotherapy with stem cell transplantation.

Therapy approaches involving biological strategies are emerging as potentially promising treatment options for patients with cancer. BL22, a recombinant immunotoxin, is a novel biological agent currently being evaluated in clinical trials for patients with hairy cell leukemia. BL22 is made up of two different biological components that are fused together through laboratory processes. One component of BL22 is a toxin that is produced by the bacteria species Pseudomonas. The second component of BL22 is a monoclonal antibody. Monoclonal antibodies are proteins that bind only to specific molecules found on the surface of a particular type of cell. The monoclonal antibody used in BL22 combines with a protein called CD22 that is found specifically on cancerous B-lymphocytes. Once the monoclonal antibody binds to the cancerous cell, the attached Pseudomonas toxin is delivered into the cell and destroys it.

One important aspect of BL22 is that it targets only B-lymphocytes, while sparing healthy cells. This is in stark contrast to chemotherapy or radiation which cause cellular destruction to healthy tissue while producing anti-cancer effects. Often, the side effects caused by chemotherapy or radiation are so severe that treatment scheduling and dosages are affected and only suboptimal regimens can be administered.

Researchers from the National Cancer Institute recently conducted a clinical trial evaluating different doses of BL22 in 16 patients who stopped responding to a standard chemotherapy agent, cladribine. Following treatment, 11 patients achieved complete disappearance of their cancer and 2 patients achieved a partial disappearance of their cancer. The 3 patients who did not respond to treatment had been given low doses of BL22 or had pre-existing antibodies to the toxin. Approximately 16 months following treatment, 3 of the 11 patients achieving complete remission experienced a cancer recurrence. These patients were re-treated with BL22 and all 3 achieved a second complete remission. Side effects caused by the treatment were transient.

These results show very promising anti-cancer effects of BL22 in patients with hairy cell leukemia who have stopped responding to cladribine. The next phase of clinical trials will begin shortly for patients with hairy cell leukemia. Additionally, patients with other forms of leukemia which are CD22 positive are currently being considered for enrollment in these trials. Patients with hairy cell leukemia may wish to speak with their physician about the risks and benefits of participation in a clinical trial evaluating BL22 or other forms of promising biological therapy. Two sources of information about ongoing clinical trials include comprehensive, easy-to-use listing services provided by the National Cancer Institute (cancer.gov) and eCancerTrials.com, which also provides personalized clinical trial searches on behalf of individuals. ( New England Journal of Medicine, Vol 345, No 4, pp 241-247, 2001)

© 1998-2005 CancerConsultants.com All Rights Reserved.

This page is an advertisement of the Consumer Justice Group, LLC. The opinions expressed herein are those of the Consumer Justice Group. The Group is a Washington, DC law firm. This website is not a solicitation for business in any other jurisdiction. The laws of the District of Columbia apply to this website. The information contained herein is not legal advice. All trademarks and copyrights are those of their respective owners.