Blenrep (belantamab mafodotin-blmf) is a brand-name prescription medication. The Food and Drug Administration (FDA) has approved it to treat certain forms of multiple myeloma (MM) in adults. Specifically, Blenrep is used to treat MM that’s refractory or has relapsed.

Here are some fast facts about Blenrep:

  • Active ingredient: belantamab mafodotin-blmf, which is a biologic
  • Drug class: B-cell maturation antigen-directed antibody
  • How it’s given: IV infusion
  • FDA approval year: 2020

If Blenrep is safe and effective for you, your doctor will likely recommend you receive it long term.

As with other drugs, Blenrep can cause side effects. Read on to learn about potential common, mild, and serious side effects. For a general overview of Blenrep, including details about its uses, see this article.

Blenrep can cause certain side effects, also called adverse effects, some of which are more common than others. These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

These are just a few of the more common side effects reported by people who took Blenrep in clinical trials:

  • changes in vision, including blurry vision
  • fatigue
  • nausea*
  • infusion-related reactions*
  • fever*

* For more information about this side effect, see “Side effect specifics” below.

Mild side effects can occur with Blenrep. This list doesn’t include all possible mild side effects of the drug. For more information, you can refer to Blenrep’s prescribing information.

Mild side effects that have been reported with Blenrep include:

  • fatigue
  • diarrhea or constipation
  • decreased appetite
  • joint or back pain
  • infection, such as the common cold
  • nausea*
  • fever*

These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you develop a side effect while taking Blenrep and want to tell the FDA about it, visit MedWatch.

* For more information about this side effect, see “Side effect specifics” below.

Blenrep may cause serious side effects. The list below may not include all possible serious side effects of the drug. For more information, you can refer to Blenrep’s prescribing information.

If you develop serious side effects while taking Blenrep, 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.

Serious side effects that have been reported and their symptoms include:

* For more information about this side effect, see “Side effect specifics” below.
Blenrep has a boxed warning for this side effect. This is a serious warning from the Food and Drug Administration (FDA).
‡ An allergic reaction is possible after receiving Blenrep. However, it’s not clear whether this side effect occurred in clinical trials.

Blenrep may cause several side effects. Here are some frequently asked questions about the drug’s side effects and their answers.

Does Blenrep cause hair loss?

No, Blenrep is not known to cause hair loss. This was not a reported side effect in clinical trials of the medication.

However, other drugs that may be used to treat multiple myeloma may cause hair loss. These include chemotherapy drugs.

If you’re experiencing hair loss during Blenrep treatment, talk with your doctor. They can help you determine what may be causing your hair loss. They may also be able to recommend ways to treat it. In some cases, they may recommend using an over-the-counter medication for your hair loss. This may include Rogaine (minoxidil).

Why do I need to have blood tests done during Blenrep treatment?

Your doctor will order blood tests during your Blenrep treatment to check for side effects.

Blenrep can decrease the levels of certain blood cells as a side effect.* These include platelets, lymphocytes, or neutrophils. Your doctor will likely monitor these blood cell levels throughout your treatment to be sure that they don’t get too low.

If your blood cell levels decrease, your doctor may recommend a lower dose of Blenrep. Or they may recommend pausing treatment until your levels increase again.

It’s important to get the blood tests that your doctor recommends. They are to help prevent side effects, including low blood cell levels, from becoming serious. Before you start Blenrep treatment, your doctor will advise how often you should have blood tests. If you have concerns about these tests, be sure to talk with your doctor.

* To learn more about this side effect, see the “Serious side effects of Blenrep” section above.

Are there long-term side effects of Blenrep?

Yes, long-term side effects of Blenrep are possible. However, most side effects reported in clinical trials were not long term.

It’s still important to be aware of the possible long-term side effects of Blenrep. This is so you can contact a doctor right away if you develop any.

Examples of long-term side effects can include:

  • joint or back pain
  • eye problems, including vision changes*
  • kidney problems†

If you’re concerned about developing any long-term side effects of Blenrep, talk with your doctor. They can discuss ways to help prevent or manage them.

* Blenrep has a boxed warning for this side effect. This is a serious warning from the Food and Drug Administration (FDA). For more information, see “Side effect specifics” below.
† To learn more about this side effect, see the “Serious side effects of Blenrep” section above.

Learn more about some of the side effects that Blenrep may cause. To find out how often side effects occurred in clinical trials, see the prescribing information for Blenrep.

Nausea

Some people may experience nausea from Blenrep treatment. In fact, nausea was one of the most common side effects reported in clinical trials of Blenrep.

In some cases, it’s also possible for nausea to be a symptom of another side effect. For example, you may experience nausea from kidney problems or a high blood calcium level. (To learn more about these side effects, see the “Serious side effects of Blenrep” section above.)

What you can do

If you experience nausea, talk with your doctor. They can help determine what may be causing your nausea and help treat it. In some cases, they may recommend taking a drug for this side effect.

Infusion-related reactions

Blenrep is given by IV infusion and may cause infusion-related reactions. These are reactions that can occur during or after a Blenrep infusion. Infusion-related reactions were common in clinical trials of Blenrep. (To learn more about how Blenrep is given, see this article.)

In some cases, infusion-related reactions can be serious. So it’s important to be aware of the possible symptoms of these reactions.

Symptoms can include:

What you can do

Throughout your Blenrep infusion, your doctor or another healthcare professional will monitor you for the above symptoms. If you notice any symptoms, tell your doctor right away.

If you experience a life threatening reaction, your doctor will likely stop Blenrep treatment. And they’ll likely recommend a different medication for your cancer.

In some cases, your doctor may recommend pausing your Blenrep infusion. And they may give you medications or other treatments to ease these reactions. Then, they may restart your infusion at a slower rate. This is to help prevent the reactions from occurring again.

Fever

It’s possible to develop a fever from Blenrep treatment. Fever was a common side effect in clinical trials of the drug.

A fever occurs when your body temperature rises above 100.4°F (38°C). You may also develop symptoms, including:

  • chills
  • sweating
  • headache
  • fatigue
  • muscle aches

What you can do

If you experience a fever during treatment with Blenrep, talk with your doctor. They will likely recommend you take an over-the-counter drug to decrease your fever, such as Tylenol (acetaminophen).

Eye problems

Some people may experience eye problems from Blenrep treatment. In fact, Blenrep has a boxed warning for ocular (eye-related) side effects. A boxed warning is a serious warning from the Food and Drug Administration (FDA). The purpose of a boxed warning is to alert doctors and patients about the risks of taking a medication. Eye problems were a common side effect reported by people taking Blenrep.

Eye problems may include:

  • changes in vision, including vision loss or blurry vision
  • dry eye
  • changes in your cornea (the outer layer of your eye)
  • eye irritation

Due to these risks, Blenrep is only available through a Risk Evaluation and Mitigation Strategies (REMS) program. The REMS program ensures both doctors and patients are aware of the possible eye problems that can occur with Blenrep treatment. It requires doctors to enroll in the program and complete certain training. The facilities where you’ll receive Blenrep must also be certified.

For you to receive Blenrep, you’ll need to enroll in the REMS program. You’ll also need to agree to monitoring for eye problems, including having regular vision exams. To learn more about the REMS program for Blenrep, see the website or call 855-209-9188. You can also talk with your doctor.

What you can do

Before and during Blenrep treatment, it’s important to follow your doctor’s monitoring guidelines. They’ll recommend having an eye exam before starting Blenrep treatment and before you receive each dose. Also, if you notice any vision changes, your doctor will recommend you get an eye exam.

If you do have any vision changes, your doctor may recommend pausing or stopping Blenrep treatment. This depends on the severity of your vision changes. If your symptoms ease, your doctor may recommend restarting your treatment. In some cases, they may prescribe a lower dose. (To learn more about Blenrep’s dosage, see this article.)

Also, your doctor will recommend using a lubricating eye drop four times a day during Blenrep treatment. This is to help prevent eye irritation. If you wear contact lenses, talk with your doctor to find out if they’re safe for you to wear during Blenrep treatment. (Contact lenses may worsen eye irritation.)

You should be careful when driving or operating other machinery during Blenrep treatment. If your vision worsens during treatment, driving and doing certain other activities may become dangerous.

If you’re concerned about eye-related side effects during Blenrep treatment, talk with your doctor.

Allergic reaction

As with most drugs, Blenrep can cause an allergic reaction in some people. However, it’s not clear whether this side effect occurred in clinical trials.

Symptoms can be mild or serious and can include:

  • skin rash
  • itching
  • flushing
  • swelling under your skin, typically in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What you can do

For mild symptoms of an allergic reaction, call your doctor right away. They may recommend ways to ease your symptoms and determine whether you should keep taking Blenrep. However, if your symptoms are serious and you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Tell your doctor about any other medical conditions that you have before starting treatment with Blenrep. They can help you determine if Blenrep may be safe for you.

Boxed warning: Eye problems

This drug has a boxed warning for the risk of eye problems, which can be severe. This is a serious warning from the Food and Drug Administration (FDA). For details, see the “Side effect specifics” section above.

Other precautions

Be sure to talk with your doctor about your health history before you start Blenrep treatment. This drug may not be the right treatment option for you if you have certain medical conditions or other factors that affect your health. These are considered drug-condition or drug-factor interactions. The conditions and factors to consider include:

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

Bleeding problems. If you’ve ever had bleeding problems, such as a blood clotting condition, tell your doctor before starting Blenrep treatment. Blenrep may decrease your blood platelet levels as a side effect.* So if you have a bleeding condition, receiving Blenrep may worsen it. If you have bleeding problems, talk with your doctor to see if it’s safe to receive Blenrep.

* For details about these side effects, see the “Side effect specifics” section above.

Alcohol with Blenrep

Blenrep isn’t known to interact with alcohol.

However, drinking alcohol may worsen certain side effects of Blenrep treatment. For example, both alcohol and Blenrep may cause nausea. So drinking alcohol during Blenrep treatment may make nausea worse.

If you’d like to drink alcohol during treatment with Blenrep, talk with your doctor. They can help determine whether it’s safe and how much is safe for you.

Pregnancy and breastfeeding while taking Blenrep

Blenrep is not safe to receive during pregnancy or breastfeeding. This medication has not been studied in pregnant people or animals. However, based on the way that the drug works in your body, it may cause fetal harm if you receive it during pregnancy.

Due to this risk, females* who can become pregnant should take a pregnancy test before starting Blenrep treatment. Also, females should use birth control during treatment and for at least 4 months after it ends.

If you’re male* and have partners who can become pregnant, you should also use birth control during Blenrep treatment. And you should use it for at least 6 months after stopping treatment.

In addition, it’s not known if Blenrep may pass into breast milk. And it is unknown what effects the drug may have on a child who is breastfed. Due to the possible risks, you should not breastfeed during Blenrep treatment. And you should not breastfeed for at least 3 months after your treatment ends.

* Sex and gender exist on spectrums. Use of the terms “female” and “male” in this article refers to sex assigned at birth.

You may experience side effects from treatment with Blenrep, some of which may be serious. It’s important that you’re aware of symptoms of side effects that you may experience so that you can alert your doctor if you notice any.

If you’d like to learn more about Blenrep, talk with your doctor or pharmacist. They can help answer any questions you have about side effects of the drug.

Besides talking with your doctor, you can do some research on your own. These articles might help:

Disclaimer: Medical News Today 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.