ofatumumab

Pronunciation: OH-fa-TOO-mue-mab
Generic name: ofatumumab
Brand names: Arzerra (discontinued), Kesimpta
Dosage form: injection for intravenous infusion, injection for subcutaneous use,
Drug classes: CD20 monoclonal antibodies, Selective immunosuppressants

Medically reviewed by Carmen Pope, BPharm. Last updated on Nov 25, 2024.

What is ofatumumab?

Ofatumumab (brand names Kesimpta and Arzerra) is a monoclonal antibody that is approved to treat multiple sclerosis (MS) under the brand name Kesimpta and chronic lymphocytic leukemia (CLL) under the brand name Arzerra. The Arzerra brand has been discontinued.

• Ofatumuab (Kesimpta brand) slows the progression and risk of relapses for specific forms of relapsing multiple sclerosis (MS). Kesimpta is a once-a-month injection given under the skin (subcutaneously) that you can self-administer in your own home.
• Ofatumuab (Arzerra brand) helps control the progression of CLL by destroying malignant B lymphocytes. Arzerra is given as an intravenous infusion by a healthcare provider on a 28-day cycle, usually in combination with other medicines.

Ofatumumab belongs to the drug class called CD20 monoclonal antibodies and targets B-cell antigens. Sometimes it is called B-cell therapy or B-cell depletion therapy. Ofatumumab works by binding to and decreasing B-cells. This slows the progression, reduces the relapse rate of MS, and depletes both normal and malignant B cells expressing CD20 in CLL.

On October 26, 2009, ofatumumab gained FDA approval for MS under the brand Kesimpta and for CLL under the brand Arzerra.

How does ofatumumab work?

Ofatumumab for MS

MS is a chronic, ongoing disease that causes damage to the brain, spinal cord, and optic nerves. This causes nerve signals to be interrupted and results in symptoms of numbness, tingling, mood changes, memory problems, pain, fatigue, blindness, and/or paralysis.

It is thought that B-cells (B-lymphocytes) play a critical role in MS which causes the immune system to attack nerves. Ofatumumab's mechanism of action for MS involves binding to and decreasing B-cells, which may slow your immune system attacking your nerves. This may decrease inflammation and reduce MS symptoms, slow your disability progression, and lower relapse rate.

Ofatumumab for CLL

Ofatumumab's mechanism of action for CLL involves targeting CD20-positive B lymphocytes. It binds to a different part of the CD20 protein than other monoclonal antibodies, which can make it effective even when similar treatments have failed. This activates the complement system to destroy cancer cells and also helps natural killer cells identify and destroy marked B cells.

Ofatumumab infusion also directly triggers cell death in targeted cells. Through these multiple mechanisms of action, ofatumumab depletes both normal and malignant B cells that express CD20. Ofatumumab belongs to the drug class called CD20 monoclonal antibodies.

What is the difference between Kesimpta and Arzerra?

Arzerra (ofatumumab) contains the same active ingredient as Kesimpta (ofatumumab) but they are NOT interchangeable. They are used to treat different conditions (Arzerra is used for CLL and Kesimpta is used for MS) and are given by different routes of administration (Arzerra is given by intravenous infusion and Kesimpta is given by subcutaneous injection).

What is ofatumumab used for?

Ofatumumab for MS

Ofatumumab (brand name Kesimpta) is used in adults with specific types of relapsing forms of multiple sclerosis (MS) including:

• clinically isolated syndrome (CIS)
• relapsing-remitting MS (RRMS)
• active secondary progressive disease (active SPMS).

Ofatumumab for CLL

Ofatumumab (brand name Arzerra) is used for CLL:

• in combination with chlorambucil, for the treatment of previously untreated patients with CLL for whom fludarabine-based therapy is considered inappropriate
• in combination with fludarabine and cyclophosphamide for the treatment of patients with relapsed CLL
• for extended treatment of patients who are in complete or partial response after at least two lines of therapy for recurrent or progressive CLL
• for the treatment of patients with CLL refractory to fludarabine and alemtuzumab.

Ofatumumab side effects

The most common ofatumumab side effects are:

• infusion-related reactions;
• irritation where the injection was given;
• fever, low blood cell counts;
• cold symptoms such as stuffy nose, sneezing, sore throat;
• cough, chest tightness, trouble breathing, lung infection;
• diarrhea, nausea;
• rash; or
• headache, tiredness.

Serious side effects and warnings

Ofatumumab can cause the following serious side effects.

Infusion-related reactions. Some side effects may occur during the ofatumumab intravenous injection (Arzerra brand) 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.

Infections. Serious infections can happen during treatment with ofatumumab. If you have an active infection, your healthcare provider should delay your treatment until your infection is gone. Ofatumumab taken before or after other medicines that weaken the immune system may increase your risk of getting infections. Tell your healthcare provider right away if you have any infections or get any symptoms, including painful and frequent urination, nasal congestion, runny nose, sore throat, fever, chills, cough, or body aches.

Hepatitis B virus (HBV) reactivation. Before starting treatment with ofatumumab, your healthcare provider will do blood tests to check for HBV. If you have ever had HBV infection, the HBV may become active again during or after treatment. Hepatitis B virus becoming active again (called reactivation) may cause serious liver problems, including liver failure or death. You should not receive this medicine if you have active hepatitis B liver disease. Your healthcare provider will monitor you for HBV infection during and after you stop using this medicine. Tell your healthcare provider right away if you get worsening tiredness or yellowing of your skin or white part of your eyes during treatment.

Progressive Multifocal Leukoencephalopathy (PML). PML may happen with ofatumumab. PML is a rare, serious brain infection caused by a virus that may get worse over days or weeks. PML can result in death or severe disability. Tell your healthcare provider right away if you have any new or worsening neurologic signs or symptoms. These may include weakness on one side of your body, loss of coordination in arms and legs, vision problems, and changes in thinking and memory which may lead to confusion and personality changes.

Weakened immune system. Ofatumumab taken before or after other medicines that weaken the immune system could increase your risk of getting infections.

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

Call your doctor at once if you have:

• signs and symptoms of infusion reactions including fever, chills, rash, or breathing problems within
  24 hours of the infusion
• pain, redness, swelling, or itching where the medicine was injected;
• symptoms of hepatitis including worsening fatigue, yellow discoloration of skin or eyes, right-sided upper stomach pain, vomiting, loss of appetite, or not feeling well;
• signs of a lung or other infection - fever, chills, cough, chest pain, feeling short of breath;
• low blood cell counts - fever, chills, tiredness, mouth sores, skin sores, easy bruising, unusual bleeding, pale skin, cold hands and feet, feeling light-headed or short of breath, petechiae, pallor, worsening weakness, or fatigue ;
• signs of tumor cell breakdown - tiredness, weakness, muscle cramps, nausea, vomiting, diarrhea, fast or slow heart rate, tingling in your hands and feet or around your mouth.
• new neurological symptoms such as confusion, dizziness or loss of balance, difficulty talking or walking, or vision problems.

To be sure ofatumumab 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.

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 the FDA at 1-800-FDA-1088.

Who should not take ofatumumab?

Do not use this medicine if you:

• have active hepatitis B virus infection
•  are allergic to ofatumumab, Arzerra, Kesimpta, or any of the inactive ingredients in the injection.

Before using ofatumumab

Before using this medicine, tell your healthcare provider about all of your medical conditions, including if you:

• have or think you have an infection including HBV or PML. 
• have ever taken, currently take, or plan to take medicines that affect your immune system. These medicines could increase your risk of getting an infection.
• have had a recent vaccination or are scheduled to receive any vaccinations.
  • You should receive any required ‘live’ or ‘live-attenuated’ vaccines at least 4 weeks before you start treatment. You should not receive ‘live’ or ‘live-attenuated’ vaccines while you are being treated with this medicine and until your healthcare provider tells you that your immune system is no longer weakened.
  • Whenever possible, you should receive any ‘non-live’ vaccines at least 2 weeks before you start treatment with ofatumumab.
  • Talk to your healthcare provider about vaccinations for your baby if you used ofatumumab during your pregnancy.
• are pregnant, think that you might be pregnant, or plan to become pregnant. 
• are breastfeeding or plan to breastfeed. 

Pregnancy

It is not known if ofatumumab will harm your unborn baby. Females who can become pregnant should use birth control (contraception) during treatment with this medicine and for 6 months after their last treatment. Talk with your healthcare provider about what birth control method is right for you during this time.

Breastfeeding

It is not known if ofatumumab passes into your breast milk. Talk to your healthcare provider about the best way to feed your baby if you take this medicine.

How should I use ofatumumab?

Ofatumumab for MS (Kesimpta brand)

See the detailed Instructions for Use that comes with ofatumumab for information about how to use the Kesimpta autoinjector and how to properly throw away (dispose of) used autoinjectors.

• Use ofatumumab exactly as your healthcare provider tells you to use it.
• Ofatumumab (brand name Kesimpta) is given as an injection under your skin (subcutaneous injection), in your thigh or stomach area (abdomen) by you or a caregiver. A caregiver may also give you an injection in your upper outer arm.
• Your healthcare provider will show you how to inject this medicine the right way before you use it for the first time.
• Do not inject into areas where the skin is tender, bruised, red, scaly or hard. Avoid areas with moles, scars, or stretch marks.
• The initial dosing is 20 mg of ofatumumab given by subcutaneous injection at Weeks 0, 1, and 2. There is no injection at Week 3. Starting at Week 4 and then every month, the recommended dose is 20 mg of ofatumumab administered by subcutaneous injection.
• If you miss an injection at Week 0, 1, or 2, talk to your healthcare provider. If you miss a monthly injection, give it as soon as possible without waiting until the next scheduled dose. After that, use your injections a month apart.

Ofatumumab for CLL (Arzerra brand)

Ofatumumab (brand name 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 ofatumumab.

Ofatumumab is usually given during 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.

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

Related/similar drugs

Imbruvica, Jaypirca, Venclexta, Vumerity, Avonex, Betaseron, Briumvi, Extavia, Ocrevus, Rebif

What other drugs will affect ofatumumab?

Tell your doctor about all your other medicines, especially drugs that weaken the immune system such as

• cancer medicine
• steroids
• medicines to prevent organ transplant rejection.

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

Who makes ofatumumab?

Novartis Pharmaceuticals Corporation makes ofatumumab for MS under the brand name Kesimpta.

Novartis Pharmaceuticals Corporation makes ofatumumab for CLL under the brand name Arzerra.

Ofatumumab Biosimilars

Biosimilar and interchangeable products are biological products that are highly similar to and have no clinically meaningful differences from the reference product.

Reference products

These are biological products that have already been approved by the FDA, against which biosimilar products are compared. There are 2 for ofatumumab.

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Further information

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