This medication is used to treat a certain blood clotting disease (hemophilia B). Hemophilia B is a genetic disorder caused by lack of a certain clotting protein (factor IX), or caused by clotting protein that does not work properly. Etranacogene dezaparvovec belongs to a class of drugs known as gene therapy. It works by helping to increase your body's production of normal factor IX. This effect may decrease bleeding problems due to hemophilia B.

This medication is given as a one-time dose. Your doctor will do lab/medical tests before and after you receive treatment to monitor for side effects and to see how well it works for you.

This product is given by slow injection into a vein as directed by your doctor. The dosage is based on your body weight. Your doctor will closely monitor you for side effects during and for at least 3 hours after the injection.

Infusion reactions may happen during the infusion of this drug. Tell your doctor right away if you have any symptoms of infusion reactions such as chest tightness, headache, abdominal pain, dizziness, lightheadedness, shaking chills, flushing, or flu-like symptoms. Your doctor may give you other medications to help with these side effects or may slow down or stop your treatment for some time.

See also How to Use section.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Etranacogene dezaparvovec may rarely cause serious (possibly fatal) liver disease. Get medical help right away if you have any symptoms of liver damage, such as:

• nausea/vomiting that doesn't stop
• loss of appetite
• stomach/abdominal pain
• yellowing eyes/skin
• dark urine

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before receiving this product, tell your doctor or pharmacist if you have any allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• liver problems (including cirrhosis, fatty liver disease, hepatitis B or C)
• increased risk of liver problems (such as due to regular overuse of alcohol)

This drug may make you dizzy. Alcohol or marijuana (cannabis) can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

This product is not usually used by women. It is unlikely to be used during pregnancy or breastfeeding. Consult your doctor if you have any questions about this product.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669.

Lab and/or medical tests (such as liver function, factor IX activity and inhibitor levels) must be done before you start and after you receive this medication. Keep all medical and lab appointments.

After receiving this treatment, do not donate blood, organs, tissues, or cells.

Not applicable.

Not applicable. This type of product is given in a hospital or clinic and will not be stored at home.

Your condition can cause complications in a medical emergency. For information about enrolling in MedicAlert, call 1-888-633-4298 (US) or 1-800-668-1507 (Canada).