This medication is used to treat a certain nervous system disorder that affects the eye (optic) nerve and spinal cord (neuromyelitis optica spectrum disorder-NMOSD). Inebilizumab belongs to a class of drugs known as monoclonal antibodies. It is not a cure for NMOSD but is thought to help by preventing immune system cells from attacking the nerves in your brain and spinal cord. This effect may help to reduce the risk of attacks and delay or slow disability.

Read the Medication Guide and, if available, the Patient Information Leaflet provided by your pharmacist before you start receiving inebilizumab and each time you get a refill. If you have any questions, ask your doctor or pharmacist.

This medication is given by slow injection into a vein as directed by your doctor. The injection is given by a health care professional, usually over about 90 minutes. The first 2 doses are usually given 2 weeks apart. Later doses are usually given every 6 months.

Infusion reactions may happen during or right after the infusion of this drug. Your doctor may prescribe other medications (such as acetaminophen, diphenhydramine, corticosteroids) before each treatment to help prevent these side effects. Tell your doctor right away if you have any symptoms of infusion reactions such as nausea, fever, flushing, mild rash/itching, shortness of breath, tiredness, headache, or muscle aches. Your doctor may give you other medications to help with these side effects or may slow down or stop your treatment for some time.

Tell your doctor if your condition does not get better or if it gets worse.

See also How to Use section.

Joint pain, back pain, or headache may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

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.

This medication may lower your ability to fight infections. This may make you more likely to get a serious (rarely fatal) infection or make any infection you have worse. Tell your doctor right away if you have any signs of infection (such as sore throat that doesn't go away, fever, chills, cough, painful/frequent urination).

This medication may increase your risk of getting a rare but very serious (possibly fatal) brain infection (progressive multifocal leukoencephalopathy-PML). Get medical help right away if you have any of these side effects:

• clumsiness
• loss of coordination/balance
• weakness
• sudden change in your thinking (such as confusion, difficulty concentrating, memory loss)
• difficulty talking/walking
• seizure
• vision changes

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 using inebilizumab, tell your doctor or pharmacist if you are allergic to it; or if you have any other 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:

• current/recent infection (especially of hepatitis B)

Inebilizumab can make you more likely to get infections or may make current infections worse. Stay away from anyone who has an infection that may easily spread (such as chickenpox, COVID-19, measles, flu). Talk to your doctor if you have been exposed to an infection or for more details.

Tell your doctor your vaccine history and ask if you need to get any vaccines before starting treatment with this medication. Your doctor may direct you to have any required vaccines at least 4 weeks before starting this medication. Tell your health care professional that you are using inebilizumab before having any immunizations/vaccinations. Avoid contact with people who have recently received live vaccines (such as flu vaccine inhaled through the nose).

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

Tell your doctor if you are pregnant or plan to become pregnant. You should not become pregnant while using inebilizumab. Inebilizumab may harm an unborn baby. Ask about reliable forms of birth control while using this medication and for 6 months after the last dose. If you become pregnant, talk to your doctor right away about the risks and benefits of this medication.

It is unknown if this medication passes into breast milk. Consult your doctor before breastfeeding.

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.

Some products that may interact with this drug are:

• other drugs that weaken the immune system/increase the risk of infection (such as natalizumab, rituximab)

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 complete blood count, tests for hepatitis B) should be done before you start using this medication and while you are using it. Keep all medical and lab appointments.

It is important to get each dose of this medication as scheduled. If you miss a dose, ask your doctor or pharmacist right away for a new dosing schedule.

Not applicable. This medication is given in a clinic or hospital 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).