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Denileukin (denileukin difitox) is a fusion protein, or a protein made from two different proteins, that is used to treat recurrent cutaneous T-cell lymphoma .


Cutaneous T-cell lymphoma (CTCL)is a form of non-Hodgkin's lymphoma, or an uncontrolled growth of cells in the lymph system that begins in the skin. It may spread to other organs.

Denileukin is known by the full name denileukin difitox, and also by the brand name Ontak. It causes the death of T cells or lymphocytes that are being made in enormous numbers by tricking the troublesome cells into binding with it, and then killing them.


Denileukin is a genetically engineered protein, created by fusing a piece of the toxin that causes diphtheria with interleukin-2 (also known as IL-2 or aldesleukin ). Because of the presence of IL-2 in the fusion protein denileukin, cells that have IL-2 receptors bind with it. Thus, the cells are fooled into binding with a protein they recognize, only to be killed by the toxin that is fused with it.

Not all malignant T cells and lymphocytes have IL-2 receptors. If the cells do not have the receptors, denileukin is not useful.

Recommended dosage

Denileukin is given through intravenous line. The best therapy course has not yet been determined. But the standard dose is either 9 or 18 micrograms per kilogram of body weight per day for five consecutive days, every three weeks.


Because the use of the treatment can contribute to an environment that encourages infections, largely because of the fluid that accumulates around cells, patients must be monitored closely for infection.

Oncologists using the treatment must first test the cells of the patient for receptivity to IL-2. The treatment should not be used in patients that do not have the specific receptors for IL-2 that tricks the cells into binding with denileukin. The receptors of the cells that will bind all have a component known as CD25.

About 60% of patients diagnosed with CTCL have the receptors for IL-2. The Food and Drug Administration (FDA) has approved denileukin for use in patients that have not responded to other treatments.

Side effects

Vascular leak, or the seepage of fluid from blood vessels, accumulates and causes swelling (edema) and may contribute to infection. Infection is an important and dangerous side effect. It causes some patients to discontinue treatment. Flu symptoms are common, and include pain, headache, and nausea and vomiting . Low blood pressure, skin eruptions, and liver toxicity (poisoning) are also side effects. Fast heart rate and numbness are possible side effects.


Denileukin was so recently approved for use that drug interaction studies are not available. As with all drugs, the physician in charge of the care plan must be told about all drugs a patient is taking that might interfere with the activity of the denileukin.

Diane M. Calabrese


Genetically engineered

An organism that has been modified by the intervention of humans, usually by the addition of DNA, or hereditary material, from one species to the DNA of another species.

Intravenous line

A tube that is inserted directly into a vein to carry medicine directly to the blood stream, bypassing the stomach and other digestive organs that might alter the medicine.


Metric measure that equals 2.2 pounds.

Lymphatic system

The system that collects and returns fluid in tissues to the blood vessels and produces defensive agents for fighting infection and invasion by foreign bodies.


One of the specialized white blood cells in the lymphatic system.


One-thousandth of a milligram, and one-millionth of a gram.


One-thousandth of a gram. There are one thousand grams in a kilogram. A gram is the metric measure that equals about 0.035 ounces.


A part of a cell that is a structural and functional fit for a compound to which the cell is exposed.


Returns, or keeps coming back.

T cell

A cell in the lymphatic system that contributes to immunity by attacking foreign bodies, such as bacteria and viruses, directly.