Key Takeaways

  • Kesimpta is a prescription drug used to treat specific types of multiple sclerosis (MS) as well as clinically isolated syndrome (CIS).
  • Common side effects of Kesimpta include back pain, upper respiratory infection, urinary tract infection, injection site reaction, and headache.
  • Serious side effects from Kesimpta are rare but may include reduced immune system activity, injection-related side effects, and progressive multifocal leukoencephalopathy (PML).

Kesimpta (ofatumumab) is used in adults to treat:

Kesimpta is a biologic drug, which means it’s made from living cells.

Keep reading to learn about the common, mild, and serious side effects Kesimpta can cause.

Some people may experience mild to serious side effects during Kesimpta treatment. Side effects can vary based on the severity of your condition and other individual factors.

Examples of Kesimpta’s commonly reported side effects include:

To learn more about some of these side effects, see the “Side effects explained” section.

Mild side effects have been reported with Kesimpta. These include:

  • back pain
  • headache
  • urinary tract infection
  • upper respiratory infection
  • injection site reaction (a reaction around the area where Kesimpta is injected)

To learn more about some of these side effects, see the “Side effects explained” section.

In most cases, these side effects should be temporary. And some may be easily managed. But if you have symptoms that are ongoing or bother you, talk with your doctor or pharmacist.

Kesimpta may cause mild side effects other than those listed here. See the drug’s prescribing information for details.

In rare cases, serious side effects can happen with Kesimpta. These may include:

To learn more about PML, see the “Side effects explained” section.

If you develop serious side effects during Kesimpta treatment, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. Sharing your experience helps make medication safer for everyone by giving doctors and researchers more information about how the drug works in real life. If you develop a side effect during treatment with Kesimpta and want to tell the FDA about it, visit MedWatch or call 800-FDA-1088.

Allergic reaction

For some people, Kesimpta can cause an allergic reaction.

In general, symptoms of allergic reaction can be mild or serious. A life threatening allergic reaction called anaphylaxis is also possible with Kesimpta.

Symptoms of allergic reaction may include:

  • swelling or irritation in your face, mouth, or throat
  • rash or itchy skin
  • wheezing or trouble breathing
  • low pulse
  • nausea
  • dizziness
  • fast heart rate

Ways to manage

For mild allergic reaction symptoms, such as a mild rash, call your doctor right away. They may recommend treatments to help manage your symptoms. They’ll also let you know whether you should keep taking the medication.

For severe allergic reaction symptoms, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms require immediate medical care because they can become life threatening. If you’ve had a serious allergic reaction to Kesimpta, your doctor will have you stop Kesimpta treatment.

Long-term side effects are possible with Kesimpta, but in most cases side effects are temporary.

Possible long-term side effects of Kesimpta include serious infections and reactivation of existing hepatitis B virus. These side effects are serious and could last a long time or require long-term treatment.

Most other side effects are temporary and may go away as your body gets used to Kesimpta or after being treated.

If you have questions about what to expect with Kesimpta treatment or side effects that last a long time or won’t go away, be sure to talk with your doctor.

Get answers to some frequently asked questions about Kesimpta’s side effects.

Are there patient reviews about Kesimpta’s side effects?

The manufacturer of Kesimpta doesn’t list side effect reviews on its website. But you can learn more about side effects reported in studies of the drug by reading Kesimpta’s prescribing information.

If you have questions or concerns about Kesimpta’s side effects, talk with your doctor.

Does Kesimpta cause hair loss?

It’s not likely. Hair loss wasn’t reported as a side effect in the drug’s studies. If you experience hair loss during treatment, it’s probably not caused by Kesimpta.

However, hair loss is a possible side effect of other medications (such as azathioprine) that are sometimes taken with Kesimpta to treat multiple sclerosis (MS).

If you’re concerned about hair loss, talk with your doctor. They can discuss possible causes and how to manage hair loss.

Could Kesimpta cause cancer?

No, Kesimpta is not known to cause cancer. This wasn’t a reported side effect in studies of the drug.

Other drugs used to treat MS may cause cancer in rare cases. For example, Ocrevus may increase the risk of certain cancers, including breast cancer. But Kesimpta is not known to affect your risk of developing cancer.

If you have questions about your cancer risk, talk with your doctor.

To learn more about how the side effects of Kesimpta and Ocrevus compare, see the following question. This Kesimpta vs. Ocrevus article also provides an in-depth comparison of the two drugs.

How do the side effects of Kesimpta compare with those of Ocrevus?

Kesimpta and Ocrevus are both approved to treat types of MS. They have some similar and a few different side effects.

Some side effects of both drugs include:

Other side effects reported with Ocrevus include:

Your doctor can provide more information about the risks and benefits of each medication, including how their side effects compare.

Learn more about some of the side effects Kesimpta may cause.

Headache

You may experience headaches during Kesimpta treatment. This was a common side effect of the drug reported in studies.

What might help

If you’re having headaches with Kesimpta, tell your doctor. They can suggest ways to manage this side effect. For example, they may suggest over-the-counter (OTC) products such as Advil (ibuprofen) or Tylenol (acetaminophen) in some cases.

Do not take any new drugs without talking with your doctor or pharmacist first. They’ll make sure there are no known interactions between Kesimpta and these other medications.

Upper respiratory infection

Because Kesimpta can reduce your immune system activity, your risk of mild to serious infection is increased during your treatment with the drug. Mild infections, such as upper respiratory infection, were commonly reported in the drug’s studies. Symptoms may include:

  • runny nose
  • cough
  • sneezing
  • mucus production

What might help

If you experience symptoms of an upper respiratory infection, call your doctor. They can discuss your symptoms with you and suggest ways to help manage them. For mild symptoms, they may suggest certain OTC medications. But you may need a prescription drug to treat more serious infections.

Be sure to discuss your symptoms with your doctor before taking any new drugs. They’ll be able to tell you whether they’re safe.

Urinary tract infection

Kesimpta can cause urinary tract infections (UTIs). This was a commonly reported side effect in the drug’s studies. Symptoms can include:

What might help

Tell your doctor if you experience symptoms of a UTI. They’ll treat your UTI and may stop your Kesimpta treatment depending on the severity of your infection.

Progressive multifocal leukoencephalopathy (PML)

Kesimpta can reduce your immune system activity, which can increase your risk of developing certain infections, including PML. This is a serious viral infection that affects certain nerve cells in the brain. This side effect was reported in the drug’s studies.

There is no known cure for PML. Symptoms include:

What might help

Tell your doctor right away if you experience symptoms of PML. Some symptoms may also be related to your condition. If you experience any of these symptoms, your doctor will stop your Kesimpta treatment and determine whether you have PML. If they confirm that you do, they’ll have you permanently stop Kesimpta.

Injection site reaction

Kesimpta can cause injection site reactions. This was a common side effect reported in the drug’s studies.

You’ll inject your dose of Kesimpta into your upper arm, your lower abdomen, or the front of your thigh. You may experience certain reactions around these areas from the injection. The risk of a reaction is highest with your first dose of Kesimpta. Examples of site reactions include:

  • itching
  • pain
  • skin redness or discoloration
  • swelling

What might help

Tell your doctor if you experience an injection site reaction with Kesimpta. They’ll recommend ways to help manage this side effect.

Do not inject Kesimpta into areas that are discolored, bruised, tender, or hard. You should also avoid injecting the drug into moles, stretch marks, or scarred areas.

Kesimpta may not be right for you if you have certain medical conditions. (This is known as a drug-condition interaction.) Other factors may also affect whether Kesimpta is a good treatment option for you. Talk with your doctor about your health history before starting Kesimpta. Factors to consider include:

  • hepatitis B
  • active infection
  • any recent vaccinations you’ve had
  • previous allergic reaction to this or a similar drug
  • pregnancy
  • breastfeeding
  • alcohol consumption

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.