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Generic name: ofatumumabOH-fa-TOO-mue-mab ]
Drug classes: CD20 monoclonal antibodies, Selective immunosuppressants

Medically reviewed by Philip Thornton, DipPharm. Last updated on Sep 22, 2023.

What is Arzerra?

Arzerra is a monoclonal antibody that affects the actions of the body's immune system. Monoclonal antibodies are made to target and destroy only certain cells in the body. This may help to protect healthy cells from damage.

Arzerra is used to treat chronic lymphocytic leukemia (CLL). In some patients, ofatumumab is given with chlorambucil, or with fludarabine and cyclophosphamide for the treatment of patients with relapsed CLL.

Arzerra is sometimes given after other medications have been tried without success.


If you have certain risk factors for hepatitis B, Arzerra can cause this condition to come back or get worse, which could lead to liver failure or death. You will need frequent blood tests to check your liver function.

Arzerra may cause a serious viral infection of the brain that can lead to disability or death. Call your doctor right away if you have any change in your mental state, decreased vision, or problems with speech or walking.

To be sure Arzerra is not causing harmful effects, your blood cells, kidney function, and liver function may need to be tested for several months, even after you stop using it. Do not miss any follow-up visits to your doctor.

Before you receive Arzerra, tell your doctor if you have hepatitis or severe COPD.

Before taking this medicine

To make sure Arzerra is safe for you, tell your doctor if you have ever had:

You may need to take antiviral medicine if you are found to have any risk factors for hepatitis B. Follow your doctor's dosing instructions very carefully.

You should be current on all vaccines before you start using Arzerra. Tell your doctor if you have received any vaccines within the past 4 weeks.

Tell your doctor if you are pregnant or planning to become pregnant.

Ofatumumab may harm an unborn baby. Use effective birth control to prevent pregnancy while using Arzerra.

If you use Arzerra while you are pregnant, make sure any doctor caring for your new baby knows that you used the medicine during pregnancy. Being exposed to ofatumumab in the womb could affect your baby's vaccination schedule during the first 6 months of life.

Using Arzerra during pregnancy could affect the immune system of the unborn baby. Tell your doctor if you are pregnant or if you become pregnant while using this medicine.

It is not known whether ofatumumab passes into breast milk or if it could harm a nursing baby. Tell your doctor if you are breast-feeding a baby.

How is Arzerra given?

Arzerra is given as an infusion into a vein. A healthcare provider will give you this injection. You may be given other medications to help prevent a reaction to the infusion. You may need to start using these medications up to 2 hours before the start of your ofatumumab infusion.

Your doctor will perform blood tests to make sure you do not have conditions that would prevent you from safely using Arzerra.

Arzerra is usually given in a 28-day treatment cycle. You may need to use the medicine only during the first 1 or 2 weeks of each cycle. Your dosing schedule may change with further doses. Your doctor will determine how long to treat you with ofatumumab.

Arzerra must be given slowly, and one infusion can take up to several hours to complete.

Read and carefully follow any Instructions for Use provided with your medicine. Ask your doctor or pharmacist if you don't understand all the instructions.

Prepare an injection only when you are ready to give it. Do not use if the medicine looks cloudy, has changed colors, or has particles in it. Call your pharmacist for new medicine.

You will need frequent medical tests while using Arzerra, and your next dose may be delayed based on the results.

If you've ever had hepatitis B, using Arzerra can cause this virus to become active or get worse. You may need frequent liver function tests while using this medicine and for several months after you stop.

What happens if I miss a dose?

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

What happens if I overdose?

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

What should I avoid while receiving Arzerra?

You should not receive a vaccine while using Arzerra. Some vaccines may not work as well and may not fully protect you from disease. Other vaccines may not be safe for you while you are using Arzerra. Vaccines include shots to prevent influenza, measles, mumps, rubella (MMR), rotavirus, typhoid, yellow fever, varicella (chickenpox), and herpes zoster (shingles).

Arzerra side effects

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

Some side effects may occur during the injection or up to 24 hours later. Tell your caregiver right away if you feel dizzy, tired, nauseated, light-headed, feverish, chilled, sweaty, itchy, or have a skin rash, headache, muscle pain, back pain, stomach pain, irregular heartbeats, chest tightness, trouble breathing, or swelling and irritation in your throat.

Ofatumumab may cause a serious brain infection that can lead to disability or death. Call your doctor right away if you have problems with speech, thought, vision, or muscle movement. These symptoms may start gradually and get worse quickly.

Call your doctor at once if you have:

Your cancer treatments may be delayed or permanently discontinued if you have certain side effects.

Common Arzerra side effects may include:

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.

What other drugs will affect Arzerra?

Tell your doctor about all your other medicines, especially:

This list is not complete. Other drugs may interact with ofatumumab, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

Popular FAQ

Arzerra (ofatumumab) is administered by an intravenous infusion. It is diluted into a sterile bag of 1000mL sodium chloride for intravenous infusion which is then hung up and the infusion administered into one of your veins via an intravenous line. How long the infusion takes depends on your stage of Chronic Lymphocytic Leukemia (CLL) and if you have had treatment before, but initially Arzerra is usually administered over about 6 hours. The time of the infusion may be shortened, depending on how well you tolerate Arzerra. Continue reading

Arzerra (ofatumumab) is approved by the FDA to treat patients with chronic lymphocytic leukemia (CLL), a type of slowly progressing cancer in your blood and bone marrow. It's an antibody therapy that works with the immune system to attack and destroy cancerous CD20-positive B cells. Continue reading

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Arzerra only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.