Enasidenib may cause a serious or life-threatening group of symptoms called differentiation syndrome. Your doctor will monitor you carefully to see whether you are developing this syndrome. If you experience any of the following symptoms, call your doctor immediately: fever, sudden weight gain, decreased urination, swelling of your arms, legs, neck, groin, or underarm area, shortness of breath, difficulty breathing, chest pain, cough, or bone pain. At the first sign that you are developing differentiation syndrome, your doctor will prescribe medications to treat the syndrome, and may tell you to stop taking enasidenib for some time.

Your doctor or pharmacist will give you the manufacturer’s patient information sheet (Medication Guide) when you begin treatment with enasidenib and each time you refill your prescription. Read the information carefully and ask your doctor or pharmacist if you have any questions. You can also visit the Food and Drug Administration (FDA) website (http://www.fda.gov/Drugs/DrugSafety/ucm085729.htm) or the manufacturer’s website to obtain the Medication Guide.

Enasidenib is used to treat a certain type of acute myeloid leukemia (AML; a type of cancer that begins in the white blood cells) that has worsened or come back after treatment with other chemotherapy medications. Enasidenib is in a class of medications called an isocitrate dehydrongenase-2 (IDH2) inhibitor. It works by slowing or stopping the growth of cancer cells.

Enasidenib comes as a tablet to take by mouth. It is usually taken once a day with or without food. Take enasidenib at around the same time every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take enasidenib exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Swallow the tablets whole with a cup (8 ounces [240 mL]) of water; do not split, chew, or crush them.

If you vomit after taking a dose of enasidenib, take another dose as soon as possible on the same day.

Your doctor may temporarily or permanently stop your treatment, decrease your dose of enasidenib, or treat you with other medications depending on the side effects that you experience. Be sure to talk to your doctor about how you are feeling during your treatment. Do not stop taking enasidenib without talking to your doctor.

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

Before taking enasidenib,

• tell your doctor and pharmacist if you are allergic to enasidenib, any other medications, or any of the ingredients in enasidenib tablets. Ask your pharmacist or check the Medication Guide for a list of the ingredients.
• tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
• tell your doctor if you are pregnant, plan to become pregnant, or plan to father a child. You should not become pregnant while you are taking enasidenib. You will need to have a negative pregnancy test before you begin taking this medication. Use effective birth control during your treatment with enasidenib and for one month after your final dose. If you are a male and your partner can become pregnant, you should use effective birth control during your treatment and for one month after your final dose. Enasidenib may decrease the effectiveness of certain oral contraceptives so talk to your doctor about birth control methods that will work for you. If you or your partner become pregnant while taking enasidenib, call your doctor.
• tell your doctor if you are breastfeeding. You should not breastfeed while you are enasidenib and for one month after your final dose.
• you should know that this medication may decrease fertility in men and women. Talk to your doctor about the risks of taking enasidenib.

Drink plenty of water or other fluids every day during your treatment with enasidenib,

Unless your doctor tells you otherwise, continue your normal diet.

Take the missed dose as soon as you remember it on the same day. However, if it is already the next day, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

Enasidenib may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• nausea
• vomiting
• diarrhea
• decreased appetite
• change in the way things taste

Some side effects can be serious. If you experience any of these symptoms or those listed in the IMPORTANT WARNING section, call your doctor immediately:

• yellowing of your eyes or skin
• muscle spasms or twitching; burning, prickling, or tingling feeling on the skin; irregular heartbeat; or seizures

Enasidenib may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom). Do not remove the desiccant (a small packet included with medication to absorb moisture) from the container.

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA’s Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can’t be awakened, immediately call emergency services at 911.

Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your body’s response to enasidenib.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.

• Idhifa^®