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Denileukin Diftitox (Ontak®)

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Please use for reference only.

OncoLink Team
Last Modified: September 23, 2015

Pronounced: DEN-i-LOO-kin DIF-ti-tox
Classification: Biologic Response Modifier

About Denileukin Diftitox

Denileukin diftitox is a type of medication called a "biologic response modifier". It is designed to target the CD25 component of the IL-2 receptor, which is found on the malignant cells of patients with certain cancers. When bound to the receptor, the drug inhibits synthesis of certain proteins, causing cell death. The medication only works in tumors that have the CD25 receptor, so testing should be done for this before starting the medication.

How to Take Denileukin Diftitox

Denileukin diftitox is given through intravenous (IV, into a vein) infusion, over a period of 30-60 minutes, but can take longer depending on the patient's reaction to the infusion. It is given for 5 consecutive days, every 21 days. The actual dose is dependent on your body size. Acetaminophen (Tylenol) and diphenhydramine (Benadryl) will be given prior to the infusion to lower the risk of an infusion reaction.

Possible Side Effects of Denileukin Diftitox

There are a number of things you can do to manage the side effects of denileukin diftitox. Talk to your doctor or nurse about these recommendations. They can help you decide what will work best for you. These are some of the most common side effects:

Infusion-Related Side Effects

The infusion can cause a reaction that may lead to chills, fever, low blood pressure, nausea and vomiting. You will receive Tylenol and diphenhydramine prior to the infusion to help prevent these reactions. Some patients will also receive a steroid before the infusion to prevent a reaction. Reactions are most common 24-48 hours after the infusion. Your doctor or nurse will tell you what to do if this happens.

Capillary Leak Syndrome

Capillary leak syndrome is a potentially serious complication in which fluids from the veins and capillaries leak into the tissue outside the bloodstream. This results in low blood pressure and poor blood flow to the internal organs. Capillary leak syndrome is characterized by the presence of 2 or more of the following 3 symptoms: low blood pressure, swelling, and low levels of protein in the blood (hypoalbuminemia). Your doctor will monitor these levels while you are taking denileukin diftitox. You should notify your doctor immediately if you notice dizziness (especially when changing position), sudden swelling or rapid weight gain, little or no urine output (for 8-12 hours), shortness of breath, difficulty breathing, irregular heart beats, or chest pain. This syndrome generally occurs within 2 weeks of treatment.

Vision Changes

This medication can lead to changes in vision, including blurry vision and a loss of color vision. While this resolved in some patients, visual changes did not resolve in most patients.


Fatigue is very common during cancer treatment and is an overwhelming feeling of exhaustion that is not usually relieved by rest. While on cancer treatment, and for a period after, you may need to adjust your schedule to manage fatigue. Plan times to rest during the day and conserve energy for more important activities. Exercise can help combat fatigue; a simple daily walk with a friend can help.  Talk to your healthcare team for helpful tips on dealing with this side effect.

Nausea and/or Vomiting

Talk to your doctor or nurse so they can prescribe medications to help you manage nausea and vomiting. In addition, dietary changes may help. Avoid things that may worsen the symptoms, such as heavy or greasy/fatty, spicy or acidic foods (lemons, tomatoes, oranges). Try antacids, (e.g. milk of magnesia, calcium tablets such as Tums), saltines, or ginger ale to lessen symptoms.

Call your doctor or nurse if you are unable to keep fluids down for more than 12 hours or if you feel lightheaded or dizzy at any time.


Your oncology team can recommend medications to relieve diarrhea. Also, try eating low-fiber, bland foods, such as white rice and boiled or baked chicken. Avoid raw fruits, vegetables, whole grain breads, cereals and seeds. Soluble fiber is found in some foods and absorbs fluid, which can help relieve diarrhea. Foods high in soluble fiber include: applesauce, bananas (ripe), canned fruit, orange sections, boiled potatoes, white rice, products made with white flour, oatmeal, cream of rice, cream of wheat, and farina. Drink 8-10 glasses on non-alcoholic, un-caffeinated fluid a day to prevent dehydration.

Reproductive Concerns

Exposure of an unborn child to this medication could cause birth defects, so you should not become pregnant or father a child while on this medication. Effective birth control is necessary during treatment.  Even if your menstrual cycle stops or you believe you are not producing sperm, you could still be fertile and conceive.  You should consult with your healthcare team before breastfeeding while receiving this medication.