Kesimpta (ofatumumab) is a prescription drug that’s used to treat multiple sclerosis. Kesimpta can cause side effects that range from mild to serious. Examples include headache, back pain, and certain infections.
Kesimpta is used in adults to treat certain types of multiple sclerosis (MS). These include:
It’s also used to treat clinically isolated syndrome (CIS), which is often (but not always) the first sign of MS.
Kesimpta is a biologic drug, which means it’s made from living cells. It contains the active ingredient ofatumumab. (An active ingredient is what makes a drug work.) Kesimpta comes as a liquid solution for injection under the skin.
Keep reading to learn about the common, mild, and serious side effects Kesimpta can cause. For a general overview of the drug, including details about its uses, see this article.
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 this side effect, see the “Side effects explained” section below.
Mild side effects have been reported with Kesimpta. These include:
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 above. See the drug’s prescribing information for details.
* To learn more about this side effect, see the “Side effects explained” section below.
† An allergic reaction is possible after using Kesimpta, but this side effect wasn’t reported in studies.
In rare cases, serious side effects can happen with Kesimpta. These may include:
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.
* To learn more about this side effect, see the “Side effects explained” section below.
† An allergic reaction is possible after using Kesimpta, but this side effect wasn’t reported in studies.
Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Kesimpta, visit MedWatch.
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 for treating 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.
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 weaken your immune system, 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 weaken your immune system, 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.
Allergic reaction
Like most drugs, Kesimpta can cause an allergic reaction in some people. But this side effect wasn’t reported in the drug’s studies. Symptoms can be mild to serious and can include:
- skin rash
- itchiness
- flushing (temporary warmth, redness, or deepening of skin color)
- swelling under your skin (usually in your eyelids, lips, hands, or feet)
- swelling of your mouth, tongue, or throat, which can make it hard to breathe
What might help
If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms. Examples include:
If your doctor confirms you’ve had a mild allergic reaction to Kesimpta, they’ll decide if you should continue using it.
If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.
If your doctor confirms you’ve had a serious allergic reaction to Kesimpta, they may have you switch to a different treatment.
Keeping track of side effects
During your Kesimpta treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start taking a new drug or using a combination of treatments.
Your side effect notes can include things such as:
- what dose of the drug you were taking when you had the side effect
- how soon you had the side effect after starting that dose
- what your symptoms were
- how your symptoms affected your daily activities
- what other medications you were taking
- any other information you feel is important
Taking notes and sharing them with your doctor will help them learn more about how Kesimpta affects you. They can then use this information to adjust your treatment plan if needed.
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 those described below.
Hepatitis B virus (HBV). Hepatitis B is a liver infection caused by the hepatitis B virus (HBV). If you’ve had an HBV infection in the past, tell your doctor. Kesimpta can increase your risk of the virus coming back. Your doctor will test you for HBV before you begin treatment with this medication.
If you have an active infection, they’ll treat the infection before you begin Kesimpta. In some cases, they may recommend a different type of treatment for your condition. This is because Kesimpta can lower your body’s ability to fight an HBV infection, which could cause serious liver damage.
Allergic reaction. If you’ve had an allergic reaction to Kesimpta or any of its ingredients, your doctor will likely not prescribe it for you. Ask them about other medications that might be better options.
Infection. Tell your doctor if you have a current infection. Because Kesimpta can lower your body’s ability to fight infections, they’ll treat your infection before having you start Kesimpta.
Recent vaccine. You should not get any live or non-live vaccines while you’re being treated with Kesimpta. Do not start Kesimpta if you’ve had a live vaccine in the past 4 weeks. Kesimpta weakens your immune system, which can increase your risk of getting an infection from the vaccine.
Tell your doctor about any vaccines you’ve had recently. They’ll likely recommend that you avoid live vaccines during Kesimpta treatment and for a while after your last dose.
Examples of live vaccines include those for:
It also includes the flu vaccine given as a nasal spray (FluMist).
Kesimpta can also weaken your response to non-live vaccines. (These don’t contain any live viruses or bacteria.) Examples include vaccines for:
It also includes the flu vaccine that’s given as an injection under your skin.
Tell your doctor if you’ve had any non-live vaccines recently. They’ll likely recommend that you wait at least 2 weeks after your last vaccine to begin Kesimpta treatment. They’ll also probably suggest that you avoid any vaccines during your treatment with this medication and for a while after your last dose.
Ask your doctor when it’s safe to take a vaccine after your treatment with Kesimpta is finished.
Alcohol and Kesimpta
There isn’t any safety information available about drinking alcohol while using Kesimpta. If you plan to drink during treatment with this drug, ask your doctor what amount, if any, is safe for you to consume.
Pregnancy and breastfeeding with Kesimpta
Kesimpta may not be safe to use while you’re pregnant or breastfeeding. Females* should use an effective type of birth control during treatment with this drug and for 6 months after their last dose.
If you’re a male,* ask your doctor about risks and birth control options while you’re using Kesimpta.
There isn’t any information about the safety of using Kesimpta while breastfeeding. Talk with your doctor to learn about any safety concerns regarding treatment with this medication while breastfeeding.
If you’re pregnant or breastfeeding, or planning to become pregnant or breastfeed, talk with your doctor. They can discuss with you the risks and benefits of Kesimpta use during these times.
* In this article, we use the terms “male” and “female” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.
Kesimpta is used to treat multiple sclerosis (MS). Some people may experience mild side effects from this drug. In rare cases, serious side effects (such as low immunoglobulins), have occurred in people using Kesimpta. If you have questions about side effects this drug can cause, talk with your doctor.
Examples of questions to help get you started include:
To learn more about Kesimpta, see these articles:
To get information on different conditions and tips for improving your health, subscribe to any of Healthline’s newsletters. You may also want to check out the online communities at Bezzy. It’s a place where people with certain conditions can find support and connect with others.
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.
