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Trade/other name(s): Arzerra

Why would this drug be used?

This drug is used to treat chronic lymphocytic leukemia. It is also being studied for use against other types of cancer and other conditions.

How does this drug work?

Ofatumumab is a type of immunotherapy known as a monoclonal antibody. A monoclonal antibody is a man-made version of an immune system protein that fits like a lock and key with a certain protein on the surface of cancer cells.

Ofatumumab is designed to seek out and lock onto the CD20 receptor, which is found on B lymphocytes (B cells) in the body. This receptor is on some normal B cells and also on B cells that are cancerous, as in chronic lymphocytic leukemia. By attaching to the cells, ofatumumab tags the cells for destruction by the body’s immune system.

Before taking this medicine

Tell your doctor…

  • If you are allergic to anything, including medicines, dyes, additives, or foods.
  • If you have ever tested positive for infection with the hepatitis B virus. This drug may cause reactivation of the infection in some people, which can be serious or even life threatening. Your doctor will want to monitor you carefully during treatment.
  • If you have any other medical conditions such as kidney disease, liver disease, heart disease, congestive heart failure, breathing problems, diabetes, gout, or infections. Your doctor may need to monitor you more closely during treatment.
  • If you are pregnant, trying to get pregnant, or if there is any chance of pregnancy. It is not known if this drug might cause problems if either the male or female is taking it at the time of conception or during pregnancy. Men and women who will be taking this drug should talk with their doctor about birth control, including what kinds of birth control can be used with this medicine. This drug should be used during pregnancy only if the potential benefit is thought to justify the potential risk to the fetus.
  • If you are breastfeeding. While no studies have been done, this drug may pass into breast milk and affect the baby.
  • If you think you might want to have children in the future. It is not known whether or not this drug can affect fertility. Talk with your doctor about the possible risk with this drug and the options that may preserve your ability to have children.
  • About any other prescription or over-the-counter medicines you are taking, including vitamins and herbs. In fact, keeping a written list of each of these medicines (including the doses of each and when you take them) with you in case of emergency may help prevent complications if you get sick.

Interactions with other drugs

No serious interactions with other drugs are known at this time, but this does not necessarily mean that none exist. Check with your doctor, nurse, or pharmacist about your other medicines, herbs, and supplements, and whether alcohol can cause problems with this medicine.

Interactions with foods

No serious interactions with food are known at this time. Check with your doctor, nurse, or pharmacist about whether some foods may be a problem.

Tell all the doctors, dentists, nurses, and pharmacists you visit that you are taking this drug.

How is this drug taken or given?

Ofatumumab is given as an infusion into a vein (IV). It is usually given for a total of 12 doses. The first 8 doses are given once a week. The final 4 doses are given once a month. The total length of treatment is about 6 months.

The first dose is 300 milligrams (mg). Later doses are 2,000 mg each. Each infusion is started slowly and the rate is increased over time if you’re not having any problems.

The first 2 infusions are given very slowly to see if you have any type of reaction to the infusion (see the Precautions section). If you aren’t having any problems, these infusions should take about 6 hours. Later infusions are given a little faster (over about 3 hours) if you aren’t having problems. Tell your nurse right away if you begin to feel different at all during any of the infusions.

You will be given medicines before each infusion to help reduce the risk of reactions, including acetaminophen (Tylenol), an antihistamine (by mouth or IV), and a corticosteroid (IV). These are given 30 minutes to 2 hours before the start of the ofatumumab infusion.


This drug can cause allergic reactions in some people when the drug is given, especially with the first 2 treatments. Mild reactions usually consist of fever and chills. More serious reactions happen rarely, but can be dangerous. Symptoms can include feeling lightheaded or dizzy (due to low blood pressure), fainting, headache, feeling warm or flushed, fever or chills, hives, itching, shortness of breath, changes in heart rate, pain the back or abdomen, or swelling of the face, tongue, or throat. Tell your doctor or nurse right away if you notice any of these symptoms during or after being given the drug. Your doctor or nurse will give you medicine before the infusion to try to prevent a reaction.

This drug may cause reactivation of hepatitis B virus (HBV) infection in some people, which can be serious or even life threatening. Your doctor may want to test your blood for signs of HBV infection before starting treatment. If your blood shows signs of an old infection, your doctor will order blood tests during your treatment to see if the virus has become active again. If it has, treatment with this drug will need to be stopped for a time. Tell your doctor or nurse right away if you notice possible symptoms of hepatitis, such as dark urine, yellowing of the skin or eyes (jaundice). This can happen up to a year or possibly even longer after the drug is finished.

This drug can cause the rapid killing of large numbers of tumor cells. When the cells die, they break open and release their contents into the bloodstream. This, called tumor lysis syndrome, can lead to kidney failure and might also affect the heart and nervous system. This is most common during the first cycle of treatment. If your doctor thinks you are at risk for this, you will get medicines and lots of fluids before and during treatment to help the body get rid of these substances. Tell your doctor or nurse if you have nausea, vomiting, diarrhea, or tiredness or if you feel weak or faint, have trouble breathing, or notice swelling after the first infusion.

Your doctor will probably test your blood throughout your treatment, looking for possible effects on blood counts (described below), kidneys, or other body organs. Based on the test results, you may be given medicines to help treat any effects. Your doctor may also need to reduce or delay your next dose of this drug, or even stop it altogether.

This drug can lower your white blood cell count, especially in the weeks after the drug is given. It may also have other effects on your immune system. This can increase your chance of getting infections. Be sure to let your doctor or nurse know right away if you have any signs of infection, such as fever, chills, pain when passing urine, new onset of cough, or bringing up sputum.

This drug may lower your platelet count in the weeks after it is given, which can increase your risk of bleeding. Speak with your doctor before taking any drugs or supplements that might affect your body’s ability to stop bleeding, such as aspirin or aspirin-containing medicines, warfarin (Coumadin), or vitamin E. Tell your doctor right away if you have unusual bruising, or bleeding such as nosebleeds, bleeding gums when you brush your teeth, or black, tarry stools.

In rare cases, use of this drug may lead to a serious brain infection known as progressive multifocal encephalopathy (PML). Tell your doctor or nurse right away if you notice any new symptoms such as confusion, feeling dizzy, loss of balance, trouble talking or walking, or vision problems.

Do not get any immunizations (vaccinations), either during or after treatment with this drug, without your doctor’s OK. This drug may affect your immune system, which could make vaccinations less effective, or could even lead to serious infections. Try to avoid contact with people who have recently received a live virus vaccine, such as the oral polio vaccine, smallpox vaccine, or nasal spray versions of the flu vaccine. Check with your doctor about this.

Rarely, this drug may cause a blockage (obstruction) in the intestines, which can stop food from passing through. Tell your doctor or nurse right away if you have symptoms such as fever, pain or bloating in the abdomen, nausea, vomiting, diarrhea, or constipation.

Possible side effects

Most of the following side effects probably will not occur. Your doctor or nurse will want to discuss specific care instructions with you. They can help you understand these side effects and help you deal with them.


  • Mild allergic reaction, especially with first 2 infusions (may include fever, chills, itching, hives, nausea, shortness of breath, mouth or facial swelling, dizziness)*
  • Infections in the lungs (pneumonia) or bronchi (bronchitis)
  • Lowered white blood cell count with increased risk of infections*
  • Fever

Less common

  • Allergic reaction with third and later infusions (same symptoms as above)*
  • Other types of infections*
  • Lowered red blood cell count (anemia)
  • Skin rash
  • Trouble sleeping
  • Feeling tired
  • Headache
  • Chills
  • Swelling in the hands or feet
  • Changes in blood pressure
  • Rapid heart rate
  • Cough
  • Shortness of breath
  • Diarrhea
  • Nausea
  • Back pain


  • Serious allergic reaction*
  • Lowered platelet count with increased risk of bleeding*
  • Reactivation of hepatitis B virus infection*
  • Tumor lysis syndrome*
  • Intestinal blockage (obstruction) *
  • Brain infection (progressive multifocal leukoencephalopathy)*
  • Death due to liver failure, brain infection, other serious infections

*See the “Precautions” section for more detailed information.

There are other side effects not listed above that can also occur in some patients. Tell your doctor or nurse if you develop these or any other problems.

FDA approval

Yes – first approved in 2009

Disclaimer: This information may not cover all possible uses, actions, precautions, side effects, or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for talking with your doctor, who is familiar with your medical needs.

Last Medical Review: 11/07/2013
Last Revised: 04/17/2014