Ofatumumab is used to treat a certain type of cancer (chronic lymphocytic leukemia - CLL). Ofatumumab belongs to a class of drugs known as monoclonal antibodies. This medication works by stopping the growth of cancer cells.

This medication is given by slow injection into a vein by a health care professional. The dosage and treatment schedule is based on your medical condition and response to treatment.

Serious (rarely fatal) infusion reactions may happen during the infusion of this drug and for up to 24 hours afterward. These reactions occur more often during the first and second treatments. Your doctor may prescribe other medications (including acetaminophen, an antihistamine such as diphenhydramine, a corticosteroid such as methylprednisolone) before each treatment to help prevent these side effects. Tell your doctor right away if you have any symptoms of infusion reactions such as chest pain, flushing, wheezing, trouble breathing, dizziness, fainting, pounding/irregular heartbeat, fever, chills, back/stomach pain, or rash/itching. Your doctor may stop your treatment for some time.

See also Warning and How to Use sections.

Nausea, vomiting, diarrhea, tiredness, swelling of hands/ankles/feet, or trouble sleeping may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

People using this medication may have serious side effects. However, you have been prescribed this drug because your doctor has judged that the benefit to you is greater than the risk of side effects. Careful monitoring by your doctor may decrease your risk.

This medication decreases bone marrow function, an effect that may lead to a low number of blood cells such as red cells, white cells, and platelets. This effect can cause anemia, decrease your body's ability to fight an infection, or cause easy bruising/bleeding. Your doctor will order blood tests to check for this side effect. It is important to keep all medical/lab test appointments. Tell your doctor right away if you develop any of the following symptoms:

• easy bruising/bleeding
• pale skin
• unusual tiredness
• signs of infection (such as sore throat that doesn't go away, fever, chills, cough)

Ofatumumab sometimes causes side effects due to the rapid destruction of cancer cells (tumor lysis syndrome). To lower your risk, your doctor may add a medication and tell you to drink plenty of fluids. Tell your doctor right away if you have symptoms such as:

• low back/side pain (flank pain)
• signs of kidney problems (such as painful urination, pink/bloody urine, change in the amount of urine)
• muscle spasms/weakness

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 medication, tell your doctor or pharmacist if you are allergic to it; or if you have ever had a severe reaction 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:

• breathing problems (such as chronic obstructive pulmonary disease - COPD, asthma)
• liver disease (such as hepatitis B)
• heart disease (such as chest pain, heart attack)
• immune system problems (such as HIV)

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).

Ofatumumab 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 health care professional that you are using ofatumumab before having any immunizations/vaccinations. Avoid contact with people who have recently received live vaccines (such as flu vaccine inhaled through the nose).

To lower the chance of getting cut, bruised, or injured, use caution with sharp objects like razors and nail cutters, and avoid activities such as contact sports.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

It is unknown if this drug 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 include:

• 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, platelets, liver/kidney function, blood mineral levels, hepatitis B virus) should be done while you are using this medication. Keep all medical and lab appointments. Consult your doctor for more details.

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 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).