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Ofatumumab (Arzerra)

Find out what ofatumumab is, how you have it and other important information about having ofatumumab.

Ofatumumab is a targeted cancer drug (biological therapy) and is also known by its brand name, Arzerra.

It is a treatment for chronic lymphocytic leukaemia (CLL). You may also have it in research trials for other types of cancer. 

How it works

Ofatumumab is a type of biological therapy called a monoclonal antibody. 

Monoclonal antibodies are copies of a single antibody. They recognise and find specific proteins on the outside of cancer cells. 

Ofatumumab targets a protein called CD20 on the surface of the chronic lymphocytic leukaemic cells. The ofatumumab sticks to all the CD20 proteins it finds. Then the cells of the immune system pick out the marked cells and kill them. 

How you have it

You have ofatumumab as a drip into your bloodstream (intravenously) through a pump. 

Drugs into your bloodstream

You have the treatment through a drip into your arm. A nurse puts a small tube (a cannula) into one of your veins and connects the drip to it.

You might need a central line. This is a long plastic tube that gives the drugs into a large vein, either in your chest or through a vein in your arm. It stays in while you’re having treatment, which may be for a few months.

When you have it

You usually have ofatumumab once a week for 8 weeks. Then you have a break with no treatment for 4 or 5 weeks. You then have ofatumumab once every 4 weeks for 4 months.

Between 30 minutes to 2 hours before you have each treatment, you have an injection of corticosteroids. You also have paracetamol and an antihistamine (either as tablets or into your bloodstream). These reduce the chance of having an allergic reaction to ofatumumab.

Your first treatment with ofatumumab is a small test dose and takes around 6 hours. If this goes well the second treatment is the full dose and again takes around 6 hours. If you don’t have any problems you may be able to have further treatments over less than 6 hours.

Tests during treatment

You have blood tests before starting treatment and during your treatment. They check your levels of blood cells and other substances in the blood. They also check how well your liver and kidneys are working.

Side effects

Important information

Other medicines, foods and drink

Cancer drugs can interact with some other medicines and herbal products. Tell your doctor or pharmacist about any medicines you are taking. This includes vitamins, herbal supplements and over the counter remedies.

Pregnancy and contraception

This drug may harm a baby developing in the womb. It is important not to become pregnant or father a child while having treatment and for a year afterwards. Talk to your doctor or nurse about effective contraception before starting treatment.


You may not be able to become pregnant or father a child after treatment with this drug. Talk to your doctor before starting treatment if you think you may want to have a baby in the future. Men may be able to store sperm before starting treatment. Women may be able to store eggs or ovarian tissue but this is rare.


Do not breastfeed during this treatment or for a year afterwards because the drug might come through in the breast milk.

Treatment for other conditions

Always tell other doctors, nurses, pharmacists or dentists that you’re having this treatment if you need treatment for anything else, including teeth problems.


Don’t have immunisations with live vaccines while you’re having treatment and for at least 6 months afterwards.

In the UK, live vaccines include rubella, mumps, measles, BCG, yellow fever and shingles vaccine (Zostavax).

You can:

  • have other vaccines, but they might not give you as much protection as usual
  • have the flu vaccine
  • be in contact with other people who've had live vaccines as injections

Avoid contact with people who’ve had live vaccines taken by mouth (oral vaccines). This includes the rotavirus vaccine given to babies. The virus is in the baby’s urine for up to 2 weeks and can make you ill. So, avoid changing their nappies for 2 weeks after their vaccination if possible. Or wear disposable gloves and wash your hands well afterwards.

You also need to avoid anyone who has had oral polio or typhoid vaccination recently.

Hepatitis B

You will have a blood test to check for hepatitis B before you start treatment. Hepatitis B is a viral infection that can cause inflammation (swelling) of the liver. Ofatumumab can make hepatitis B infection active again. Your doctor may treat you with an anti viral treatment to prevent this. 

Tell your doctor if you have had hepatitis in the past.


Ofatumumab contains sodium. You will need to take account of this if you are on a controlled sodium diet.

More information about this treatment

For further information about this treatment go to the electronic Medicines Compendium (eMC) website.

You can report any side effect you have to the Medicines Health and Regulatory Authority (MHRA) as part of their Yellow Card Scheme.

Information and help

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