According to a recent article published in an early online edition of the Journal of Clinical Oncology, the biologic agent Ontak® (denileukin diftitox) appears effective for some patients with relapsed non-Hodgkin’s lymphoma.

Non-Hodgkin’s lymphoma (NHL) is a form of cancer that begins in the cells of the lymph system. The lymph system includes the spleen, thymus, tonsils, bone marrow, lymph nodes and circulating immune cells. The main cells in the lymph system are lymphocytes, of which there are two types: B and T-cells. B-cells and T-cells have a very specific function in aiding the body to fight infection. NHL is characterized by the excessive accumulation of atypical (cancerous) lymphocytes. These lymphocytes can crowd the lymph system and suppress the formation and function of other immune and blood cells. Most cases of NHL involve B-cells and may be referred to as B-cell NHL. While NHL is categorized by the type of lymphocyte it involves, it is also further defined by the rate at which the cancer grows, based on the appearance of the cells under a microscope. High-grade or aggressive NHL is the fastest growing and low-grade or indolent lymphoma is the slowest growing.

Recurrent lymphoma is cancer that has returned following therapy and refractory lymphoma is cancer that has stopped responding to standard therapies. Researchers continue to evaluate novel therapeutic approaches for patients with recurrent NHL, including newer agents referred to as biologic therapies.

Ontak® is a biologic agent that is approved for the treatment of cutaneous T-cell lymphoma. Ontak® is a type of agent that is comprised of two separate proteins that have been fused together through laboratory processes. One of the proteins that make up Ontak® is a laboratory-derived poison (toxin) that is identical to the toxin produced by the bacteria Corynebacterium diphtheriae, commonly known as diphtheria. The other protein segment of Ontak® is called interleukin-2 (IL-2), which is a naturally occurring immune substance responsible for stimulating some immune processes. The IL-2 segment of Ontak® binds to IL-2 receptors (CD25 antigen) on lymphocytes (both normal and cancerous) and then delivers the diphtheria toxin into the cell. Once inside, the toxin destroys the cell. Ontak® is currently in clinical trials for the treatment of various cancers.

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Researchers from the University of Texas M.D. Anderson Cancer Center recently conducted a clinical trial to evaluate Ontak® in the treatment of B-cell NHL that had stopped responding to standard therapies. This trial included 45 patients, 71% of whom did not respond to their last chemotherapy treatment and all of whom were previously treated with the biologic agent Rituxan® (rituximab). Following treatment with Ontak®, nearly one-quarter (24.5%) of patients achieved a partial or complete disappearance of their cancer and an additional 20% achieved a stabilization of their cancer. The average duration of anti-cancer responses on Ontak® was 7 months and progression-free survival was 24% at 20 months. Side effects caused by Ontak® were generally mild and reversible.

The researchers concluded that Ontak® produces clinical responses in a substantial portion of patients with recurrent B-cell NHL and is generally well-tolerated. The researchers state that treatment with Ontak® for recurrent or refractory NHL should be further pursued in future clinical trials, either alone or in combination with other treatments.

Patients with B-cell NHL that has stopped responding to standard therapies may wish to speak with their physician about their individual risks and benefits of participating in a clinical trial further evaluating Ontak® or other promising therapeutic agents. Two sources of information regarding ongoing clinical trials include the National Cancer Institute (cancer.gov) and www.cancerconsultants.com. Personalized clinical trial searches are also performed on behalf of patients at cancerconsultants.com.

Reference: Dang N, Hagemeister F, Pro B, et al. Phase II study of denieleukin diftitox for relapsed/refractory B-cell non-Hodgkin’s lymphoma. Journal of Clinical Oncology. 2004. Early online publication available at: http://www.jco.org/cgi/content/abstract/JCO.2004.03.071v1. Accessed September 2004.

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