Koselugo (selumetinib) is a prescription drug approved to treat a type of nerve tumor in certain children. Koselugo comes as an oral capsule.

Specifically, doctors prescribe Koselugo to treat plexiform neurofibromas (PN) in children ages 2 years and older with a genetic disorder called neurofibromatosis type 1 (NF1). PN is a type of nerve tumor that is not cancerous.

To learn more about Koselugo’s uses, see the “Uses for Koselugo” section.

Koselugo basics

Koselugo contains the active ingredient selumetinib. It belongs to a group of drugs called kinase inhibitors.

Koselugo is a brand-name medication. A generic version of the drug isn’t currently available.

Doctors prescribe Koselugo to treat nerve tumors called plexiform neurofibromas (PN) in certain children ages 2 years and older. These children have neurofibromatosis type 1 (NF1). Koselugo treats PN tumors that cause symptoms and can’t be removed fully with surgery.

NF1 is a rare genetic disorder that raises the risk of developing benign (not cancerous) and malignant (cancerous) tumors. These include PN tumors, which are benign and develop along the nerves. They may form near the surface of the skin or deeper inside the body. Children with NF1 may be born with these tumors.

Depending on where the tumors are located, they may cause symptoms such as:

  • a lump under the skin
  • pain
  • numbness
  • weakness

They may also cause other symptoms, such as problems with:

  • movement
  • hearing
  • vision
  • using a toilet
  • eating

Koselugo works to treat PN by blocking the action of certain irregular proteins that encourage the tumors to grow. This helps shrink the tumors, which may ease the symptoms they cause.

Like most drugs, Koselugo may cause mild to serious side effects. The following lists contain some of the more common side effects Koselugo may cause, but they don’t include all the possible side effects.

Keep in mind that the side effects of a drug can depend on:

  • your age
  • other health conditions you have
  • other medications you take

Your doctor or pharmacist can tell you more about potential Koselugo side effects. They can also suggest ways to help reduce side effects.

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 medications safer for everyone. It gives doctors and researchers more information about how the drug works in real life. If you develop a side effect while taking Koselugo and want to tell the FDA about it, visit MedWatch or call 800-FDA-1088.

Mild side effects

Here’s a list of some of the mild side effects that Koselugo can cause. To learn about other mild side effects, talk with your child’s doctor or pharmacist. Or read Koselugo’s prescribing information.

Mild side effects of Koselugo that have been reported include:

Mild side effects of many drugs may go away within a few days to a couple of weeks. But if they become bothersome, talk with your child’s doctor or pharmacist.

Serious side effects

Serious side effects from Koselugo can occur, but they aren’t common. If your child has serious side effects from Koselugo, call their doctor right away. If you think your child is having a medical emergency, you should call 911 or your local emergency number.

Serious side effects of Koselugo that have been reported include:

  • severe skin rash
  • severe diarrhea
  • digestive system problems, such as colitis (bowel inflammation)
  • reduced amount of blood pumped from the heart with each beat
  • eye problems, including cataracts and ocular hypertension (increased pressure in the eye)
  • muscle damage
Allergic reaction

For some people, Koselugo can cause an allergic reaction. But this side effect wasn’t reported in the drug’s studies.

In general, symptoms of an allergic reaction can be mild or serious.

What might help

If your child has mild symptoms of an allergic reaction, such as a mild rash, call their doctor right away. They may suggest a treatment to manage your child’s symptoms. They can also determine whether your child should continue Koselugo treatment.

If your child has symptoms of a severe allergic reaction, such as swelling or difficulty breathing, call 911. Or call your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

Your doctor can confirm whether your child has had a serious allergic reaction to Koselugo. If they have, the doctor may switch them to a different treatment.

The Koselugo dosage your child’s doctor prescribes will depend on several factors. These include:

  • your child’s body surface area in square meters (m²), which your doctor will calculate using your child’s height and weight
  • other medical conditions your child may have
  • other medications your child may take
  • certain side effects your child may have with Koselugo

The following information describes dosages that are commonly used or recommended. But be sure to use the dosage your child’s doctor prescribes for your child. Your child’s doctor will determine the best dosage to fit your child’s needs.

Form and strengths

Koselugo is available as an oral capsule in two strengths: 10 milligrams (mg) and 25 mg.

Dosage for PN in children with NF1

For treating PN in children ages 2 years and older with NF1, your child’s doctor will likely prescribe 25 mg per m² twice daily.

Your child’s doctor will calculate the right dosage based on your child’s height and weight.

About taking Koselugo

The following are some common questions about taking Koselugo.

  • Can Koselugo be chewed, crushed, or split? No, you should not chew, crush, or split Koselugo capsules. Your child should swallow them whole. If they have difficulty doing so, you can get tips on how to swallow pills. Or you can ask your child’s doctor or pharmacist for advice.
  • Should my child take Koselugo with food? You can take Koselugo with or without food.
  • Is there a best time of day to take Koselugo? You should take Koselugo twice daily. This means your child should take it in the morning and evening, approximately 12 hours apart. It’s best to take it around the same times each day. This helps keep a steady level of the drug in the body, which helps Koselugo work effectively.
  • What if I miss a dose of Koselugo? If your child misses a dose of Koselugo, check when their next dose is due. If the next dose is due in more than 6 hours, they should take the missed dose as soon as possible. But if the next dose is due in less than 6 hours, skip the missed dose and then give them their next dose at its usual time. Your child should not take two doses at once to make up for a missed dose. Doing so could raise their risk of side effects.
  • Will my child need to take Koselugo long term? Koselugo is typically a long-term treatment. You and your child’s doctor can determine whether it’s safe and effective for your child’s condition. If you agree that it is, your child will likely take it long term.
  • How long does Koselugo take to work? Koselugo begins to work soon after your child takes their first dose. But they likely won’t feel the drug working. And it may take several months for their symptoms to ease or reduce. Your child’s doctor will order tests throughout treatment to check whether Koselugo is working to treat your child’s condition.

Overdose

Do not give your child more Koselugo than your child’s doctor prescribes. Doing so could lead to harmful effects.

What to do in case of overdose

Call your doctor if you think your child has taken too much Koselugo. You can also call 800-222-1222 to reach America’s Poison Centers or use its online resource. But if your child has severe symptoms, immediately call 911 or your local emergency number. Or go to the nearest emergency room.

Koselugo can interact with several other medications. It can also interact with certain supplements and foods.

Before starting Koselugo, talk with your child’s doctor and pharmacist. Tell them about all prescription, over-the-counter, and other drugs your child takes. Also tell them about any vitamins, herbs, or supplements your child takes. Sharing this information can help avoid potential interactions.

Interactions with medications, foods, and supplements

The following table highlights medications, supplements, and foods that can interact with Koselugo. This list does not contain all drugs that may interact with Koselugo. If you have questions about interactions that may affect your child, ask your child’s doctor or pharmacist.

Medications that can interact with Koselugo• certain antifungals, such as fluconazole (Diflucan) and itraconazole (Sporanox)

• certain antibiotics, such as clarithromycin and rifampin (Rifadin, Rimactane)

• certain HIV medications, such as ritonavir (Norvir) and cobicistat (Tybost)

• the antidepressant nefazodone

• certain seizure medications, such as phenytoin (Dilantin, Phenytek) and carbamazepine (Tegretol, others)

• certain blood thinners, such as warfarin (Jantoven) or clopidogrel (Plavix)
Vitamins or supplements that can interact with Koselugo• St. John’s wort

• vitamin E
Foods that can interact with Koselugo• grapefruit and grapefruit juice

Koselugo and alcohol

Alcohol is not known to interact with Koselugo. But drinking alcohol could worsen certain side effects of Koselugo. These include:

  • nausea
  • diarrhea
  • headache

If you have questions about alcohol use with Koselugo, talk with your doctor or your child’s doctor.

Whether or not you have health insurance, cost may be a factor when you’re considering Koselugo. What you’ll pay for Koselugo may depend on several things, such as your child’s treatment plan and the pharmacy you use.

A few things to consider regarding Koselugo’s price are:

  • Generic form: Koselugo is not currently available as a generic drug. Generics usually cost less than brand-name drugs.
  • Savings program: If you have questions about how to pay for your child’s prescription, talk with your child’s doctor or pharmacist. A program called OneSource may also be available.

The following is important information to consider and discuss with your child’s doctor or pharmacist before starting Koselugo.

Pregnancy and Koselugo

Koselugo may cause fetal harm if taken during pregnancy. If your child is able to become pregnant, talk with their doctor before they start this drug. The doctor may suggest birth control options to use during treatment with Koselugo.

Birth control and Koselugo

Koselugo may cause fetal harm if taken during pregnancy. Therefore, if your child is sexually active and they or their partner can become pregnant, talk with their doctor about birth control options during Koselugo treatment.

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

For females taking Koselugo

It’s recommended that females who can become pregnant use birth control during treatment with Koselugo. It’s also recommended that they use it for at least 1 week after taking the last dose.

For males taking Koselugo

Males with partners who can become pregnant should use birth control during treatment with Koselugo and for at least 1 week after the last dose.

Koselugo and breastfeeding

Breastfeeding is not recommended while taking Koselugo and for 1 week after the last dose. You can talk with your healthcare team for more information.

Before your child starts taking Koselugo, discuss their health history with their doctor. Koselugo may not be right for your child if they have certain medical conditions or other factors affecting their health. Be sure to talk with your child’s doctor if any of the following apply to your child:

Note: For more information about the potential negative effects of Koselugo, see the “Side effects of Koselugo” section.

Here are answers to some commonly asked questions about Koselugo.

Can Koselugo be used for adults?

Koselugo is not approved for use in adults. Doctors prescribe Koselugo to treat PN in children ages 2 years and older with the genetic disorder NF1. PN is a type of nerve tumor that is not cancerous.

But doctors sometimes may prescribe Koselugo off-label to treat PN in adults with NF1. (Off-label use is when doctors prescribe a drug for a purpose other than what it’s approved to treat or help prevent.)

If you’re an adult with NF1, talk with your doctor about whether Koselugo may be right for you.

Who is the manufacturer of Koselugo?

Alexion Pharmaceuticals, which specializes in treatments for rare diseases, manufactures Koselugo. Alexion is part of AstraZeneca Rare Disease. AstraZeneca partners with Merck to develop and market Koselugo.

Is Koselugo chemotherapy?

No, Koselugo is not chemotherapy. Instead, it’s a type of treatment called targeted therapy.

Chemotherapy is a traditional treatment for tumors. It works by killing all cells that are multiplying quickly in your body. Because of this, it can include healthy cells as well as tumor cells and cause many side effects.

Targeted therapies such as Koselugo block specific proteins or processes that help tumor cells multiply quickly. Compared to chemotherapy, these therapies tend to cause fewer effects on healthy cells in your body and thus fewer side effects. But they still can cause mild and serious side effects. (See the “Side effects of Koselugo” section for Koselugo’s side effect details.)

Other drugs, such as mirdametinib (Gomekli), are available that can treat your condition. If you’d like to explore an alternative to Koselugo, talk with your doctor. They can tell you about other medications that might work well for you.

Disclaimer: MyistyClan 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.