Key takeaways

  • Epkinly is a prescription drug used to treat certain forms of B-cell lymphoma. More common side effects include injection site reactions, muscle and bone pain, and fatigue. These side effects may be temporary, lasting a few days to weeks.
  • This drug carries a risk of potentially serious side effects including cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS).
  • It’s important to promptly report any side effects to your doctor, as severe reactions like CRS and ICANS may require you to stop Epkinly treatment.

Epkinly (epcoritamab-bysp) is used to treat the following conditions in adults:

For both of these conditions, Epkinly is used after two systemic (affecting the whole body) treatments have been tried and either they didn’t work or the cancer returned.

Note: Epkinly received accelerated approval from the Food and Drug Administration (FDA) for these uses based on early studies. Full approval is typically granted after the completion of further studies. If you have questions about this, talk with your doctor.

Epkinly comes as a liquid solution that’s given as an injection under your skin by a healthcare professional.

Epkinly contains the active ingredient epcoritamab-bysp. (The reason “-bysp” appears at the end of the drug’s name is to show that it’s distinct from similar medications that may be created in the future.)

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

This drug has boxed warnings for the risk of cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS). Boxed warnings are the most serious warnings from the Food and Drug Administration (FDA). For details, see the “Side effects explained” section.

The following list contains a few of the more common side effects reported by people receiving Epkinly in studies. Side effects can vary depending on the condition being treated.

The following were common side effects seen in those receiving Epkinly treatment for both of the drug’s indications (uses):

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

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

  • abdominal pain
  • constipation
  • cough
  • diarrhea
  • fatigue
  • fever
  • headache
  • injection site reactions, such as pain, swelling, skin rash, or itchiness
  • muscle, bone, or joint pain
  • nausea and vomiting
  • reduced appetite
  • skin rash
  • swelling caused by fluid buildup

In most cases, these side effects should be temporary. And some may be easily managed. But if you have symptoms that are ongoing or bothersome, talk with your doctor or pharmacist. And do not stop Epkinly treatment unless your doctor recommends it.

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

Serious side effects have been reported with Epkinly. These include:

If you develop serious side effects during Epkinly 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.

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 while taking Epkinly and want to tell the FDA about it, visit MedWatch or call 800-FDA-1088.

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

How do side effects of Epkinly compare with those of Rituxan?

Epkinly and Rituxan (rituximab) are both used to treat certain types of B-cell lymphoma, but their mechanism of action (how they work) is different. Epkinly is a form of immunotherapy, which is a treatment that helps your immune system attack cancer cells. Rituxan is a targeted therapy that directly attacks cancer cells. Neither drug is traditional chemotherapy.

These drugs can cause some similar side effects. For example, both can increase your risk of serious infection. But they can also cause some different side effects. For instance, Epkinly can cause CRS* and ICANS*, while Rituxan can cause serious heart, skin, kidney, and bowel problems and infusion-related reactions.

To learn more about how the side effects of these treatments compare, talk with your doctor.

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

Does Epkinly cause long-term side effects?

It’s possible. Long-term side effects include those that may start any time during treatment with a drug, even if you’ve been receiving it for a long time. They also include side effects that may not go away, even after you stop treatment.

Examples of long-term side effects reported in Epkinly’s studies include:

  • low platelet count, which can cause bruising or bleeding problems
  • low red blood cell count, which can cause tiredness and shortness of breath
  • low white blood cell count, which can increase the risk of infection

These side effects can continue for as long as you receive Epkinly injections. They may also last a long time after you’ve stopped treatment with this medication.

Talk with your doctor to learn more about possible side effects of Epkinly and how long they may last.

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

Risk of CRS

Epkinly has a boxed warning about the risk of CRS. A boxed warning is the most serious warning from the FDA. It alerts doctors and patients about drug effects that may be dangerous.

CRS was a common side effect reported in studies of Epkinly. CRS is usually mild, but in rare cases it can be severe or even life threatening.

CRS occurs when high levels of immune system proteins called cytokines are released in your body. Cytokines can cause inflammation in tissues and organs throughout your body, which can disrupt normal bodily functions.

CRS may cause symptoms such as:

CRS typically occurs within 24 hours of receiving a dose of Epkinly. It’s most likely to occur with the first four doses, especially with the third dose (which is the first full dose). Symptoms of CRS usually improve within a few days.

What might help

To help prevent CRS, your doctor will increase your Epkinly dose slowly over your first three doses. They’ll also prescribe medications to help prevent CRS before each of your first four Epkinly doses.

For example, you may be given:

If you have CRS with any of your first four Epkinly doses, your doctor may also prescribe these preventive medications before future doses.

Additionally, you’ll need to stay in the hospital for 24 hours after receiving your third dose of Epkinly (since this will be your first full dose and the most likely dose to cause CRS). This allows healthcare professionals to monitor you and treat any CRS symptoms if needed.

If you have symptoms of CRS after receiving any other dose of Epkinly, tell your doctor. They’ll decide whether you need treatment in a hospital. You should not drive or operate machinery until your symptoms have fully resolved.

If you have CRS, your doctor may delay your next Epkinly dose until your symptoms improve. But if you have severe CRS, your doctor will likely recommend stopping Epkinly treatment.

Risk of ICANS

Epkinly has a boxed warning about the risk of ICANS. A boxed warning is the most serious warning from the FDA. It alerts doctors and patients about drug effects that may be dangerous.

ICANS was a common side effect reported in studies of Epkinly. It causes symptoms that affect your brain and nerves. It’s usually mild, but in rare cases it can be severe or even life threatening.

ICANS may cause symptoms such as:

ICANS can occur within 2 weeks of receiving a dose of Epkinly and is most likely to occur with the first four doses. Symptoms of ICANS usually improve after a few days.

What might help

If you have symptoms of ICANS after receiving a dose of Epkinly, tell your doctor. They’ll decide whether you need treatment in a hospital. You should not drive or operate machinery until your symptoms have fully resolved.

If you have ICANS, your doctor may delay your next Epkinly dose until your symptoms improve. But if you have severe ICANS, your doctor will likely recommend stopping Epkinly treatment.

Allergic reaction

Like most drugs, Epkinly may cause an allergic reaction in some people. However, 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 difficult 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:

  • an antihistamine you swallow, such as Benadryl (diphenhydramine)
  • a product you apply to your skin, such as hydrocortisone cream

If your doctor confirms you’ve had a mild allergic reaction to Epkinly, they’ll decide whether you should continue treatment.

If you have symptoms of a severe allergic reaction, such as swelling or difficulty 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 Epkinly, they may have you switch to a different treatment.

The following is important information you should consider before starting treatment with Epkinly.

Boxed warnings

Epkinly has boxed warnings about the risk of CRS and ICANS. Boxed warnings are the most serious warnings from the FDA.

Risk of CRS: Epkinly can cause CRS, which is a side effect caused by high levels of inflammatory proteins called cytokines in your body. It can be severe or even life threatening.

Risk of ICANS: Epkinly can cause ICANS, which is a side effect affecting your brain and nerves. It can be severe or even life threatening.

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

Other warnings

Epkinly can sometimes cause harmful effects in people with certain conditions. This is known as a drug-condition interaction. Other factors may also affect whether Epkinly is a good treatment option for you.

Talk with your doctor about your health history before starting this drug. Be sure to tell them if any of the following factors apply to you:

  • severe kidney or liver problems
  • infection
  • past allergic reaction to Epkinly
  • pregnancy
  • breastfeeding

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.