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 Jan 17, 2025.

What is ofatumumab?

Ofatumumab is used 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.

• Ofatumumab slows the progression and risk of relapses for specific forms of relapsing multiple sclerosis (MS) when administered as Kesimpta, once a month.
• Ofatumumab was also used to help control the progression of CLL as Arzerra, but it is now discontinued.

Ofatumumab received FDA approval on October 26, 2009 under the brand name Kesimpta for MS and Arzerra for CLL.

How does ofatumumab work?

Ofatumumab's mechanism of action is thought to involve binding to and decreasing numbers of B cells. These are a type of white blood cell called B-lymphocytes that produce antibodies and are more abundant in people with MS, particularly those with active disease. Kesimpta binds to CD20, a protein on the surface of pre-B and mature B cells, triggering their destruction. By reducing numbers of B-cells Kesimpta slows the progression and reduces the relapse rate of MS. In CLL, Arzerra depletes both normal and malignant B cells expressing CD20.

Ofatumumab belongs to the drug class called CD20 monoclonal antibodies.

Indications and FDA approvals

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 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.

Related/similar drugs

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?

MS (Kesimpta brand)

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

• Use exactly as directed by your healthcare provider.
• Ofatumumab 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 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.

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?

Ofatumumab is made by Novartis, a multinational pharmaceutical company headquartered in Basel, Switzerland. Novartis was founded in 1996 through the merger of Ciba-Geigy and Sandoz. Some of Novartis's other notable medications include:

• Entresto (for heart failure)
• Cosentyx (for psoriasis and arthritis)
• Gilenya (for multiple sclerosis)
• Zolgensma (for spinal muscular atrophy)
• Leqvio (for cholesterol management)
• Xolair (for asthma and allergic conditions)
• Tasigna (for leukemia)
• Tafinlar (for melanoma)
• Promacta (for blood disorders)
• Kisqali (for breast cancer).

Commercials for ofatumumab have featured various actresses, most notably Jamie-Lynn Sigler, best known for her role as Meadow Soprano on The Sopranos (HBO). Sigler also has MS.

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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