Pronunciation: key-simp-ta
Generic name: ofatumumab
Dosage form: 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 Kesimpta?

Kesimpta (ofatumumab) is an FDA-approved medicine used to slow the progression and risk of relapses for specific forms of relapsing multiple sclerosis (MS). It is a once-a-month injection given under the skin (subcutaneously) that you can self-administer in your own home.

Kesimpta'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 the destruction of the cell. Kesimpta will not cure MS but clinical trials show it slows its progression and reduces the rate of relapse.

Kesimpta belongs to the drug class called CD20 monoclonal antibodies. Kesimpta may also be called a selective immunosuppressant.

Kesimpta gained FDA approval on October 26, 2009. There is no Kesimpta generic (more correctly called a biosimilar). 

What is Kesimpta used for?

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).

Clinical trials have shown Kesimpta starts to work to lower B cells within a week. Symptoms of MS may take a bit longer to resolve.

Important Note: Arzerra Vs Kesimpta

Although Arzerra contains the same active ingredient as Kesimpta (ofatumumab), they are NOT interchangeable.

• They are used to treat different conditions (Arzerra is used for CLL and Kesimpta is used for MS).
• They are given by different routes of administration (Arzerra is given by intravenous infusion and Kesimpta is given by subcutaneous injection).

Kesimpta side effects

The most common side effects of Kesimpta are:

• upper respiratory tract infections (these are typically viral infections that cause sneezing, nasal congestion, a headache, and a sore throat)
• headache.

See What are 8 key Kesimpta side effects to watch out for?

Serious side effects and warnings

Kesimpta can cause the following serious side effects.

Infections. Clinical trials have reported serious infections associated with Kesimpta. If you have an active infection, your healthcare provider should delay your treatment until your infection is gone. Kesimpta 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, your healthcare provider will do blood tests to check for HBV. If you have ever had an 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 this medicine. 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. Kesimpta taken before or after other medicines that weaken the immune system could increase your risk of getting infections.

Injection-related reactions. Injection-related reactions are a common side effect of Kesimpta. These can happen within 24 hours (1 day) following the first injection and with later injections. There are 2 kinds of reactions:

• at or near the injection site: redness of the skin, swelling, itching and pain. Talk with your healthcare
  provider if you have any of these signs and symptoms.
• those that may happen when certain substances are released in your body: fever, headache, pain in the muscles, chills, tiredness, rash, hives, trouble breathing, swelling of the face, eyelids, lips, mouth, tongue and throat, and feeling faint, or chest tightness. Contact your healthcare provider right away if you experience any of these signs and symptoms, especially if they become worse or you have new severe signs of reactions after subsequent injections. It could be a sign of an allergic reaction, which can be serious.

Low immunoglobulins. Kesimpta may cause a decrease in some types of antibodies. Your healthcare provider will do blood tests to check your blood immunoglobulin levels.

These are not all the possible side effects of Kesimpta. Call your healthcare provider for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Related/similar drugs

Before using Kesimpta

Do not use Kesimpta if you:

• have an active hepatitis B virus infection
• have had an allergic reaction to ofatumumab or a life-threatening injection-related reaction to Kesimpta.

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 Kesimpta.
  • Talk to your healthcare provider about vaccinations for your baby if you used Kesimpta during your pregnancy.
• are pregnant, think you might be pregnant, or plan to become pregnant
• are breastfeeding or plan to breastfeed.

Pregnancy

It is not known if this medicine 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 your 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 this medicine 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 Kesimpta?

See the detailed Instructions for Use that come with the Kesimpta Package Insert for information about how to prepare and inject a dose of this medicine and how to properly throw away (dispose of) used pens or prefilled syringes.

• Use Kesimpta exactly as your healthcare provider tells you to use it.
• 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. See Where and how is Kesimpta injected? for more information.
• Your healthcare provider will show you how to prepare and 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.

Kesimpta dosing

• Initial dosing: Kesimpta 20 mg of Kesimpta given by subcutaneous injection at Weeks 0, 1, and 2.
• Subsequent dosing: Kesimpta 20 mg administered monthly starting at week 4.
• There is no injection at Week 3.

What happens if I miss a dose?

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 Kesimpta?

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 Kesimpta, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here. Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements. Know the medicines you take. Keep a list of them to show your healthcare provider and pharmacist when you get a new medicine.

How should I store Kesimpta?

Store Kesimpta in a refrigerator between 36°F to 46°F (2°C to 8°C). Keep it in the original carton until ready for use to protect it from light.

If needed, Kesimpta may be stored for up to 7 days at room temperature, up to 86°F (30°C ). Write the date taken out of the refrigerator in the space provided on the carton.

If stored below 86°F (30°C), unused Kesimpta may be returned to the refrigerator and must be used within the next 7 days. If this Kesimpta is not used within those 7 days, then discard the medicine.

Do not freeze. Do not shake.

Keep Kesimpta and all medicines out of the reach of children.

What are the ingredients in Kesimpta?

Active ingredient: ofatumumab
Inactive ingredients: Sensoready pen and prefilled syringe: arginine, disodium edetate, polysorbate 80, sodium acetate trihydrate, sodium chloride, and Water for Injection. Hydrochloric acid may be added.

Available as Kesimpta 20 mg/0.4 mL solution in a single-dose prefilled Sensoready Pen and Kesimpta 20 mg/0.4 mL solution in a single-dose prefilled syringe.

Who makes Kesimpta?

Kesimpta 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 Kesimpta 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.

Kesimpta 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 Kesimpta.

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