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Denileukin Diftitox

(den-ih-loo-kin dif-tih-toks)

Trade/other name(s): Ontak

Why would this drug be used?

This drug is used to treat certain patients with a type of non-Hodgkin lymphoma of the skin (cutaneous T-cell lymphoma). It is being studied to see if it is useful against other types of cancer.

How does this drug work?

Denileukin diftitox is a type of immunotherapy. It is a man-made piece of an immune system protein (interleukin-2, or IL-2) attached to fragments of diphtheria toxin. Once inside the body, the IL-2 portion of the drug attaches to the surface of cancer cells that have the IL-2 receptor protein (known as CD25). The toxin part of the drug then stops the cell from making new proteins, which causes cell death.

Before taking this medicine

Tell your doctor…

  • If you are allergic to anything, including medicines, dyes, additives, or foods.
  • If you have any medical conditions such as kidney disease, liver disease (including hepatitis), heart disease, congestive heart failure, diabetes, gout, or infections. These conditions may require that your medicine dose, regimen, or timing be changed.
  • If you are pregnant, trying to get pregnant, or if there is any chance of pregnancy. It is not known if this drug may cause birth defects if either the male or female is taking it at the time of conception or during pregnancy. Check with your doctor about what kinds of birth control can be used with this medicine.
  • If you are breast-feeding. It is not known if this drug passes into breast milk or whether or not it could affect the baby. Breast-feeding is not recommended while you are using this medicine.
  • If you think you might want to have children in the future. It is not known if this drug reduces fertility. Talk with your doctor about the possible risk with this drug and the options that may preserve your ability to have children.
  • About any other prescription or over-the-counter medicines you are taking, including vitamins and herbs. In fact, keeping a written list of each of these medicines (including the doses of each and when you take them) with you in case of emergency may help prevent complications if you get sick.

Interactions with other drugs

No serious interactions are known at this time. But this does not necessarily mean that none exist.

Check with your doctor, nurse, or pharmacist about your other medicines, herbs, and supplements, and whether alcohol can cause problems with this medicine.

Interactions with foods

No serious interactions with food are known at this time. Check with your doctor, nurse, or pharmacist about whether some foods may be a problem.

Tell all the doctors, dentists, nurses, and pharmacists you visit that you are taking this drug.

How is this drug taken or given?

Denileukin diftitox is given as an infusion into a vein, over at least 15 minutes. (It may be longer if you have any possible symptoms of an infusion reaction – see Precautions below.) You will usually get medicines to try and prevent allergic reactions before you get the drug. Treatment is given daily for 5 days in a row. This may be repeated every 3 weeks. The dose depends on your body size and other factors.


This drug can cause allergic reactions in some people during or within 24 hours of when the drug is given. Symptoms can include feeling lightheaded or dizzy (due to low blood pressure), fever or chills, flushing, chest pain, back pain, hives, increased heart rate, or shortness of breath. In rare cases these reactions can be serious. Tell your doctor or nurse right away if you notice any of these symptoms during or after being given the drug. Your doctor or nurse may give you medicine beforehand to try to prevent a reaction.

This drug can lower your white blood cell count, especially in the weeks after the drug is given. This can increase your chance of getting an infection. Be sure to let your doctor or nurse know right away if you have any signs of infection, such as fever (100.5° or higher), chills, pain when passing urine, a new cough, or bringing up sputum.

This drug may cause blood vessels to become leaky within the first few weeks after treatment. The leaky vessels allow protein-rich fluid to move from the blood into body tissues. This can cause low blood pressure and fluid may collect in your feet, abdomen, or in your lungs. Tell your doctor or nurse right away if you become dizzy or if you have shortness of breath, swelling in your hands or feet, rapid weight gain, or low urine output.

Some people who have received this drug have reported some loss of sharpness of vision and/or loss of color vision. This may be permanent.

Your doctor will probably test your blood throughout your treatment, looking for possible effects of the drug on blood counts (described below) or on other body organs. Based on the test results, you may be given medicines to help treat any effects. Your doctor may also need to reduce or delay your next dose of this drug, or even stop it altogether. Be sure to keep all your appointments for lab tests and doctor visits.

This drug may lower your red blood cell count. If this occurs, it is usually a few weeks after starting treatment. A low red blood cell count (known as anemia) can cause shortness of breath, or make you feel weak or tired all the time. Your doctor may give you medicines to help prevent or treat this condition, or you may need to get blood transfusions.

Do not get any immunizations (vaccines), either during or after treatment with this drug, without your doctor's OK. Denileukin diftitox may affect your immune system. This could make vaccinations ineffective, or could even lead to serious infections if you get a live virus vaccine during or soon after treatment. Try to avoid contact with people who have recently received a live virus vaccine, such as the oral polio vaccine or smallpox vaccine. Check with your doctor about this.

Possible side effects

You will probably not have most of the following side effects, but if you have any talk to your doctor or nurse. They can help you understand the side effects and cope with them.


  • drug reaction within 24 hours of infusion (may include low blood pressure, increased heart rate, shortness of breath, chest pain, back pain)*
  • fever and chills, weakness, aches in muscles (flu-like symptoms)
  • rash
  • infection*
  • feeling weak
  • poor appetite
  • nausea and/or vomiting
  • low blood pressure, rapid weight gain, and swelling of feet or other parts of the body*

Less common

  • diarrhea
  • sweating
  • flushing
  • rapid heart rate
  • low red blood cell count with risk of anemia and tiredness (fatigue)*
  • loss of appetite
  • weight loss
  • trouble breathing*
  • abnormal blood test results which suggest that the drug is affecting the liver (Your doctor will discuss the importance of this finding, if any.)
  • cough
  • sore throat
  • runny nose
  • low calcium level in the blood
  • itching
  • serious allergic reaction*


  • vision changes*
  • nervousness
  • confusion
  • trouble sleeping
  • constipation
  • blood clots
  • blood in the urine
  • protein in the urine
  • increase in blood pressure
  • abnormal blood test results which suggest that the drug is affecting the kidneys (Your doctor will discuss the importance of this finding, if any.)
  • death due to allergic reaction, leaky blood vessels, or other cause

*See "Precautions" section for more detailed information.

There are other side effects not listed above that can also occur in some patients. Tell your doctor or nurse if you develop these or any other problems.

FDA approval

Yes – first approved in 1999.

Disclaimer: This information does not cover all possible uses, actions, precautions, side effects, or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for talking with your doctor, who is familiar with your medical needs.

Last Medical Review: 02/11/2010
Last Revised: 02/11/2010