If you have a certain kind of cancer, your doctor might suggest Libtayo as a treatment option for you.

Libtayo is a prescription medication that’s used to treat certain forms of the following cancers in adults:

For each of these uses, you’ll likely receive Libtayo until your cancer worsens or you have bothersome side effects.

Libtayo is a biologic, which is a drug that’s made from parts of living organisms. The active ingredient in Libtayo is cemiplimab-rwlc. An active ingredient is what makes a drug work.

This drug comes as a solution that a healthcare professional gives as an intravenous (IV) infusion. This is an injection of medication into a vein given over a period of time.

For more information about Libtayo, including details about its uses, see this in-depth article on the drug.

Like other drugs, Libtayo can cause mild to serious side effects (also called adverse effects). Keep reading to learn more.

Some people may experience mild to serious side effects during their Libtayo treatment. Examples of Libtayo’s commonly reported side effects include:

These are just a few side effects Libtayo may cause. Additional side effects of Libtayo, mild and serious, are listed below.

Like most medications, Libtayo can cause mild side effects.

Examples of mild side effects that have been reported with Libtayo include:

* To learn more about this side effect, see the “Side effects explained” section below.

In most cases, these side effects should be temporary. And some may be easily managed, too. But if you have any symptoms that are ongoing or bother you, talk with your doctor or pharmacist. And don’t stop using Libtayo unless your doctor recommends it.

Libtayo may cause mild side effects other than the ones listed above. See the Libtayo prescribing information for details.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Libtayo, visit MedWatch.

Although rare, Libtayo may cause serious side effects.

Serious side effects that have been reported with Libtayo include:

* To learn more about this side effect, see the “Side effects explained” section below.

If you develop serious side effects during Libtayo 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.

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

Infusion reactions

You’ll receive Libtayo as an intravenous (IV) infusion (an injection of medication into a vein given over time). As a result, you may have infusion reactions from treatment with this drug. These are reactions that occur during or immediately after receiving a Libtayo IV infusion.

Serious infusion reactions were very rare in studies of Libtayo, but may still happen.

The most common infusion reactions reported in these studies include:

Other infusion reactions are possible, such as:

What might help

A healthcare professional will monitor you during your Libtayo infusions. If you have symptoms of an infusion reaction, they’ll likely slow down or pause the infusion. They may also recommend treatment for your symptoms.

But if your infusion reaction is severe, a healthcare professional will likely recommend you stop treatment with Libtayo.

Immune reactions

Libtayo treats cancer by increasing activity in your immune system. But in rare cases, this can cause your immune system to attack parts of your body by mistake. This is known as an immune reaction (also called immune-mediated reaction).

These reactions were rare in studies of Libtayo. But in extreme cases, they may lead to hospitalization or even be fatal.

Symptoms of an immune reaction are different from an allergic reaction (see “Allergic reaction” below). These symptoms vary depending on which part of your body is affected.

Immune reactions caused by Libtayo may affect any organ in your body. It’s possible to have more than one immune reaction at the same time.

These reactions may occur at any time during your Libtayo treatment. It’s also possible for them to occur even after your last dose of the drug, although this is rare.

The table below lists examples of immune reactions and symptoms reported in studies of Libtayo.

Libtayo immune reactionPossible symptoms
colitis• belly pain
bloody stool
• loose or more frequent bowel movements
hepatitisyellowing of your skin or the whites of your eyes
• nausea and vomiting
• pain on the right side of your belly
nephritisbloody urine
making less urine than usual
• swelling in your ankles or lower legs
pneumonitischest pain
• cough
• trouble breathing
thyroiditis• behavior or mood changes
feeling cold
hair loss
• weight changes

What might help

If you notice symptoms of an immune reaction while using Libtayo, contact your doctor right away. Depending on the severity of your symptoms, they’ll likely either pause or permanently stop Libtayo treatments.

To help lessen symptoms, your doctor may also prescribe treatments such as a corticosteroid. An example of this type of drug is prednisone.

Blood disorders

Blood disorders are possible with Libtayo treatment. Though rare, serious cases were reported in studies of Libtayo. These include:

These blood disorders may not cause symptoms unless they become serious. Often, mild blood disorders are only detected through results of lab tests.

What might help

During your treatment with Libtayo, your doctor will have you get blood tests. These tests will check blood levels of various substances to see if any are too high or too low.

Depending on the results, your doctor may prescribe treatment to correct levels of certain substances. They may also temporarily pause your Libtayo treatment.

Urinary tract infection

It’s possible to have a urinary tract infection (UTI) as a side effect of Libtayo.

These infections weren’t common in studies of Libtayo. But they can be serious in rare cases.

Symptoms of a mild UTI can include:

Symptoms of a more serious UTI may include:

  • fever or chills
  • pain in your upper back and sides
  • nausea and vomiting

What might help

If you notice symptoms of a UTI while you’re receiving Libtayo, contact your doctor right away. They’ll likely want to test your urine for infection. This test also helps them determine the best treatment for your UTI.

Your doctor will also recommend whether you should continue receiving Libtayo while treating your UTI.

Allergic reaction

Like most drugs, Libtayo can cause an allergic reaction in some people. This side effect was rare in studies of Libtayo.

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. To manage symptoms, they may suggest an over-the-counter antihistamine you take by mouth, such as Benadryl (diphenhydramine). Or they may recommend a product you apply to your skin, such as hydrocortisone cream.

If your doctor confirms you had a mild allergic reaction to Libtayo, 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 had a serious allergic reaction to Libtayo, they may have you switch to a different treatment.

Keeping track of side effects

During your Libtayo treatment, consider keeping 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 new drugs or using a combination of treatments.

Your side effect notes can include things such as:

  • what dose of 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 it affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Keeping notes and sharing them with your doctor will help them learn more about how Libtayo affects you. They can then use this information to adjust your treatment plan if needed.

Libtayo may not be right for you if you have certain medical conditions or other factors that affect your health. Talk with your doctor about your health history before starting Libtayo. The list below includes factors to consider.

Autoimmune conditions. Libtayo can cause immune system problems. If you have an autoimmune condition, such as lupus, you may have a higher risk of this Libtayo side effect. Your condition may also worsen from using this drug. Before you start Libtayo treatment, tell your doctor about any autoimmune conditions you have. This will help them determine whether Libtayo is safe for you.

Organ or stem cell transplant. If you’ve had an organ transplant or certain kind of stem cell transplant, taking Libtayo may result in serious side effects. For example, Libtayo may cause your body to reject an organ transplant. If you’ve had either type of transplant, your doctor will likely not prescribe Libtayo. They’ll discuss safer treatment options with you instead.

Nervous system conditions. Treatment with Libtayo can result in immune system problems. This may worsen existing nervous system conditions, such as myasthenia gravis. Tell your doctor about any nervous system conditions you have. They can discuss with you whether Libtayo is a safe treatment option.

Allergic reaction. If you’ve had an allergic reaction to Libtayo or any of its ingredients, your doctor will likely not prescribe Libtayo. Ask them what other medications are better options for you.

Alcohol and Libtayo

There’s no known interaction between using Libtayo and drinking alcohol.

But alcohol could worsen or increase the risk of certain Libtayo side effects, including:

If you drink alcohol, talk with your doctor about how much is safe to consume while you’re receiving Libtayo.

Pregnancy and breastfeeding while receiving Libtayo

Libtayo is not safe to use during pregnancy or while breastfeeding.

If you can become pregnant, your doctor will give you a pregnancy test before prescribing Libtayo. They’ll also recommend you use effective birth control while receiving the drug and for at least 4 months after your last dose.

Your doctor will also recommend that you avoid breastfeeding during Libtayo treatment and for at least 4 months after your last dose.

Like most drugs, Libtayo can cause side effects, including some serious ones in rare cases.

If you’re interested in learning more about the side effects of Libtayo, talk with your doctor or pharmacist. Ask questions to get the answers you need to feel confident about your cancer treatment. Here are a few examples to consider:

  • Are there ways I can lower my risk of side effects from Libtayo?
  • Do other medications I take raise my risk of side effects with Libtayo?
  • How do Libtayo’s side effects compare with those of other treatments for my condition?


Will Libtayo cause my hair to fall out?



It’s very unlikely. Hair loss wasn’t a side effect reported in studies of Libtayo.

But hair loss can be a symptom of thyroid or hormone gland problems. In rare cases, Libtayo can cause immune reactions that affect the thyroid or other hormone glands. With immune reactions, your immune system mistakenly attacks parts of your body. These reactions are different from an allergic reaction. Immune reactions can cause hair loss as well as other symptoms.

If you notice hair loss during Libtayo treatment, contact your doctor. This may be a sign of a thyroid or hormone gland problem. If your doctor confirms you’re having an immune reaction to Libtayo, they will likely pause or permanently stop your Libtayo treatment.

The Healthline Pharmacist TeamAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.
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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.