Emapalumab is used together with a medicine called dexamethasone to treat hemophagocytic lymphohistiocytosis (HLH), a rare disease that is sometimes inherited. HLH causes your immune system to attack healthy blood cells, which can lead to serious or life-threatening side effects on your spleen or liver. Emapalumab is for use in adults and children as young as newborn.

Emapalumab is given after other treatments did not work or have stopped working.

Emapalumab may also be used for purposes not listed in this medication guide.

Emapalumab affects your immune system. You may get infections more easily, even serious or fatal infections. Call your doctor if you have a fever, chills, night sweats, skin sores, cough, trouble breathing, or cough with bloody mucus.

Before you start treatment with emapalumab, your doctor may perform tests to make sure you do not have tuberculosis or other infections.

Emapalumab is given as an infusion into a vein, usually once every 3 or 4 days. A healthcare provider will give you this injection.

emapalumab must be given slowly, and the infusion can take about 1 hour to complete.

Emapalumab affects your immune system. You may get infections more easily, even serious or fatal infections. You will need blood tests to help your doctor determine how long to treat you with this medicine.

You may be given other medications to help prevent serious infections. Keep using these medicines for as long as your doctor has prescribed.

Tell your doctor if you have ever had tuberculosis or if anyone in your household has tuberculosis. Also tell your doctor if you have recently traveled. Tuberculosis and some fungal infections are more common in certain parts of the world, and you may have been exposed during travel.

Tell your doctor if you have ever had:

• a positive tuberculosis (TB) skin test;

• any type of infection (active or recent);

• histoplasmosis (a fungal infection);

• herpes zoster (shingles); or

• if you are scheduled to receive a vaccine.

Tell your doctor if you are pregnant or breastfeeding.

Call your doctor for instructions if you miss an appointment for your emapalumab injection.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Do not receive a "live" vaccine while using emapalumab and for at least 4 weeks after your last dose. Live vaccines include measles, mumps, rubella (MMR), polio, rotavirus, typhoid, yellow fever, varicella (chickenpox), zoster (shingles), and nasal flu (influenza) vaccine.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Some side effects may occur during the injection. Tell your caregiver if you feel feverish, chilled, sweaty, itchy, light-headed, nauseated, or if you have chest pain, shortness of breath, or skin rash or redness.

You may get infections more easily, even serious or fatal infections. Call your doctor right away if you have signs of infection such as:

• fever, chills, night sweats;

• loss of appetite, weight loss;

• feeling very tired;

• warmth, redness, or painful sores on your skin;

• cough, trouble breathing;

• mouth and throat ulcers;

• cough with bloody mucus; or

• any other new or worsening signs of infection.

Common side effects of emapalumab may include:

• fever; or

• increased blood pressure.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Other drugs may affect emapalumab, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.