Selpercatinib (Retsevmo)

Selpercatinib is a targeted cancer drug. It is also known as Retsevmo.

You pronounce selpercatinib as sel-per-ka-ti-nib.

It is a treatment for advanced Open a glossary item:

  • non small cell lung cancer that has not been treated with a RET tyrosine kinase inhibitor drug (TKI) Open a glossary item
  • thyroid cancer that has come back after treatment with lenvatinib or sorafenib
  • medullary thyroid cancer

You might have selpercatinib if:

  • your cancer has spread or can’t be removed by surgery AND
  • you have a RET gene (mutation). You have tests on the cancer cells to check for this gene change 

How does selpercatinib work?

Certain cancers have changes in the RET gene. This causes the body to make an abnormal RET protein. This protein can cause cells to grow out of control and lead to cancer. Selpercatinib blocks this protein, so may slow the growth of the cancer or help to shrink the cancer.  

How do you take selpercatinib?

Selpercatinib is a capsule that you take by mouth.

If you are on medicines to relieve heartburn, acid reflux or gastroesophageal reflux disease (GERD) you may have to take selpercatinib differently.

You must take tablets according to the instructions your doctor or pharmacist gives you.

You should take the right dose, not more or less.

Talk to your healthcare team before you stop taking a cancer drug, or if you miss a dose.

How often do you have selpercatinib?

You take selpercatinib twice a day, in the morning and evening. 

You continue taking selpercatinib for as long as the treatment is working and you are not experiencing too many side effects. 


You have blood tests before and during your treatment. They check your levels of blood cells and other substances in the blood. They also check how well your liver and kidneys are working.

You also have tests to check your heart before and during treatment. The test is called an ECG Open a glossary item.

What are the side effects of selpercatinib?

Side effects can vary from person to person. They also depend on what other treatments you're having. 

When to contact your team

Your doctor, nurse or pharmacist will go through the possible side effects. They will monitor you during treatment and check how you are at your appointments. Contact your advice line as soon as possible if:

  • you have severe side effects 

  • your side effects aren’t getting any better

  • your side effects are getting worse

Early treatment can help manage side effects better. 

Contact your advice line immediately if you have signs of infection, including a temperature above 37.5C or below 36C.

We haven't listed all the side effects here. Remember it is very unlikely that you will have all of these side effects. But you might have some of them at the same time.

Common side effects

These side effects happen in more than 10 in 100 people (more than 10%). You might have one or more of them. They include:

Increased risk of infection 

Increased risk of getting an infection is due to a drop in white blood cells. Symptoms include a change in temperature, aching muscles, headaches, feeling cold and shivery and generally unwell. You might have other symptoms depending on where the infection is.

Infections can sometimes be life threatening. You should contact your advice line urgently if you think you have an infection. 

Diarrhoea or constipation 

Tell your healthcare team if you have diarrhoea or constipation. They can give you medicine to help. 

Tiredness (fatigue)

Tiredness and weakness (fatigue) can happen during and after treatment. Doing gentle exercises each day can keep your energy up. Don't push yourself, rest when you start to feel tired and ask others for help.

Feeling or being sick

Feeling or being sick is usually well controlled with anti sickness medicines. It might help to avoid fatty or fried foods, eat small meals and snacks and take regular sips of water. Relaxation techniques might also help.

It is important to take anti sickness medicines as prescribed even if you don’t feel sick. It is easier to prevent sickness rather than treat it once it has started.

Loss of appetite

You might lose your appetite for various reasons while having cancer treatment. Sickness, taste changes or tiredness can put you off food and drinks.

Fluid build up (oedema)

A build up of fluid may cause swelling in your arms, hands, ankles, legs, face and other parts of the body. Contact your healthcare team if this happens to you.

Dry Mouth 

A dry mouth is also called xerostomia (pronounced zero-stow-mee-a). Talk to your healthcare team if you have this. They can give you artificial saliva to help with a dry mouth. It can also help to drink plenty of fluids.

High levels of creatinine in your blood

Your blood tests might show that you have high levels of a substance called creatinine.

Creatinine is a waste product made by the muscles. The kidneys remove this from our blood and get rid of it in our urine. You have blood tests to check the levels of creatinine.

Changes to the way your heart works 

You might have changes to your heart rate or rhythm. You have regular ECG tests to check the electrical activity of your heart. 


These drugs can cause bleeding from anywhere in your body. This is usually mild but there is a risk of a serious bleed. Signs of bleeding include blood in your urine or poo (stool), black stool, vomiting or coughing up blood, headaches, dizziness or feeling weak.

Contact your doctor or nurse straight away if you have any signs of bleeding.

High temperature (fever)

If you get a high temperature, let your healthcare team know straight away. Ask them if you can take paracetamol to help lower your temperature.

Skin rash 

Tell your doctor if you have any rashes or itching, particularly if your rash becomes red, painful or looks like acne.

Moisturising your skin regularly helps to reduce the risk of skin side effects. Your doctor or nurse will tell you what lotions, creams or gels to use.

Don't go swimming if you have a rash as the chlorine in the water can make it worse.

Cover up and use a high factor sunblock if you’re going out in the sun.

Do not use products to treat acne.


Let your doctor or nurse know if you have headaches. They can give you painkillers such as paracetamol to help.


This drug might make you feel dizzy. You might also feel dizzy when standing or moving around. Or it might feel like the world is spinning.

Don’t drive or operate machinery if you have this.

High blood pressure

Tell your doctor or nurse if you have headaches, nosebleeds, blurred or double vision or shortness of breath. Your nurse checks your blood pressure regularly. 

Changes in levels of minerals in your blood

You might have changes in levels of minerals in your blood, such as low magnesium. You have regular blood tests during treatment to check this.

Liver changes 

The changes are usually very mild and unlikely to cause symptoms. They will almost certainly go back to normal when treatment is finished. 

You have regular blood tests throughout your treatment so your doctor can check this.

Tummy (abdominal) pain

You might have pain in your tummy including upper or lower tummy pain. Tell your treatment team if you have this. They can check the cause and give you medicine to help. 

Occasional side effects

Between 1 and 10 out of every 100 people (between 1 and 10%) might have an allergic reaction with selpercatinib. Symptoms of an allergic reaction include a rash, shortness of breath, redness or swelling of the face and dizziness.

Some allergic reactions can be life threatening, alert your nurse or doctor straightaway if notice any of these symptoms.

Coping with side effects

We have more information about side effects and tips on how to cope with them.

What else do you need to know?

Other medicines, food and drink 

Cancer drugs can interact with medicines, herbal products, and some food and drinks. We are unable to list all the possible interactions that may happen. An example is grapefruit or grapefruit juice which can increase the side effects of certain drugs.

Tell your healthcare team about any medicines you are taking. This includes vitamins, herbal supplements and over the counter remedies. Also let them know about any other medical conditions or allergies you may have.

Loss of fertility 

It is not known whether this treatment affects fertility Open a glossary item in people. Talk to your doctor before starting treatment if you think you may want to have a baby in the future.

Pregnancy and contraception 

This drug may harm a baby developing in your womb. It is important not to become pregnant or get someone pregnant while you are having treatment with this drug and for at least 1 week afterwards.

Talk to your doctor or nurse about effective contraception before starting treatment. Let them know straight away if you or your partner become pregnant while having treatment.


It is not known whether this drug comes through into the breast milk. Doctors usually advise that you don’t breastfeed during this treatment and for at least 1 week after your last dose. 

Other conditions

If you are having tests or treatment for anything else, always mention your cancer treatment. For example, if you are visiting your dentist.


Don’t have immunisations with live vaccines while you’re having treatment and for up to 12 months afterwards. The length of time depends on the treatment you are having. Ask your doctor or pharmacist how long you should avoid live vaccinations.

In the UK, live vaccines include rubella, mumps, measles, BCG, yellow fever and one of the shingles vaccines called Zostavax.

You can have:

  • other vaccines, but they might not give you as much protection as usual
  • the flu vaccine (as an injection)
  • the coronavirus (COVID-19) vaccine - talk to your doctor or pharmacist about the best time to have it in relation to your cancer treatment

Members of your household who are aged 5 years or over are also able to have the COVID-19 vaccine. This is to help lower your risk of getting COVID-19 while having cancer treatment and until your immune system Open a glossary item recovers from treatment.

Contact with others who have had immunisations - You can be in contact with other people who have had live vaccines as injections. Avoid close contact with people who have recently had live vaccines taken by mouth (oral vaccines) such as the oral typhoid vaccine. Sometimes people who have had the live shingles vaccine can get a shingles type rash. If this happens they should keep the area covered.

If your immune system is severely weakened, you should avoid contact with children who have had the flu vaccine as a nasal spray as this is a live vaccine. This is for 2 weeks following their vaccination.

Babies have the live rotavirus vaccine. The virus is in the baby’s poo for about 2 weeks and could make you ill if your immunity is low. Get someone else to change their nappies during this time if you can. If this isn't possible, wash your hands well after changing their nappy.

More information about this treatment

For further information about this treatment and possible side effects go to the electronic Medicines Compendium (eMC) website. You can find the patient information leaflet on this website.

You can report any side effect you have to the Medicines Health and Regulatory Authority (MHRA) as part of their Yellow Card Scheme.

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