Belzutifan (WELIREG®)

Belzutifan comes in tablets. This means you can take it at home.

You may have it with other cancer drugs.

During a course of treatment, you will meet someone from your cancer team, such as a:

• cancer doctor
• specialist nurse
• specialist pharmacist.

This is who we mean when we mention doctor, nurse or pharmacist in this information.

During your course of treatment, you will have regular blood tests. This is to check that it is safe for you to have treatment.

You will meet with a doctor, nurse or pharmacist before you have treatment. They will talk to you about your blood results and ask how you have been feeling. If your blood results are okay, the pharmacy team will prepare your targeted therapy. .

You take belzutifan once a day, every day. You usually keep taking this treatment as long as it is effective and the side effects are manageable.

Your cancer team will discuss your treatment plan with you. They will give you the tablets to take home. Always take them exactly as they tell you to. This is important to make sure they work as well as possible for you.

Your cancer team may also give you anti-sickness drugs and other medicines to take home. Take all your tablets exactly as they tell you to.

Belzutifan can be taken with or without food.

Make sure you:

• swallow them whole with a glass of water
• do not chew, break or crush them
• take them at the same time every day.

If you forget to take the tablets, take the missed dose as soon as possible within the same day. If a full day has passed, do not take a double dose. Contact the hospital on the 24-hour number you have been given for advice.

Other things to remember about your tablets:

• Keep them in the original package and at room temperature, away from moisture, heat and direct sunlight.
• Keep them safe, where children cannot see or reach them.
• If you are sick (vomit) just after taking them, do not take an extra dose. Take your next dose at the usual time.
• Do not throw away unused tablets. Return them to your cancer team at the hospital.

This treatment can reduce the number of red blood cells in your blood. Red blood cells carry oxygen around the body. If the number of red blood cells is low, this is called anaemia. You may feel:

• very low in energy
• breathless 
• dizzy and light-headed. 

If you have these symptoms, contact the hospital straight away on the 24-hour number. You may need treatment for anaemia. If you are very anaemic, you may need a drip to give you extra red blood cells. This is called a blood transfusion.

Belzutifan can cause lower than normal oxygen levels in the body. Your doctor, nurse or pharmacist can talk to you more about this. Your cancer team will check your blood oxygen levels before starting belzutifan and regularly throughout treatment. If you have any of the following symptoms, contact the hospital straight away on the 24-hour number:

• cough
• breathlessness
• fast heart rate
• feeling agitated or confused.

It is important to follow any specific advice your cancer treatment team gives you. Always call 999 if you are struggling to breathe.

Smoking increases your risk of low oxygen levels and breathing problems. If you smoke, ask your doctor, nurse or pharmacist for advice about stopping.

Feeling tired is a common side effect of this treatment. Try to pace yourself and plan your day so you have time to rest. Gentle exercise, like short walks, can help you feel less tired.

If you feel sleepy, do not drive or use machinery.

You may feel sick during this treatment, but this is usually mild. Your doctor, nurse or pharmacist may prescribe you anti-sickness drugs to help prevent or control sickness. Take the drugs exactly as they tell you to. If you feel sick, take small sips of fluid often and eat small amounts regularly. It is important to drink enough fluids.

If you continue to feel sick, or if you are sick (vomit) 1 to 2 times in 24 hours, contact the hospital on the 24-hour number as soon as possible. They will give you advice.

This treatment may cause headaches. If you have headaches, tell your doctor, nurse or pharmacist. They can give you advice about painkillers that may help. Tell them if the headache does not get better, or gets worse.

Cancer and some cancer treatments can increase the risk of a blood clot. Contact the hospital straight away on the 24-hour number if you have any of these symptoms during or after treatment:

• throbbing pain or swelling in a leg or arm
• reddening of the skin in the area – if you have black or brown skin, this can be harder to notice, but the skin might become darker
• suddenly feeling breathless or coughing.

Always call 999 if you have:

• chest pain
• difficulty breathing.

A blood clot is serious, but it can be treated with drugs called anticoagulants. These thin the blood. Your doctor, nurse or pharmacist can give you more information about preventing and treating blood clots.

Some medicines can affect how this treatment works or be harmful while you are having it. Always tell your cancer doctor, nurse or pharmacist about any drugs you are taking or planning to take, such as: 

• medicines you have been prescribed
• medicines you buy in a shop, pharmacy or online
• vitamins or supplements 
• herbal drugs and complementary or homeopathic therapies
• recreational drugs – for example, cannabis.

Cancer doctors usually recommend that people with cancer have vaccinations for flu and coronavirus (covid). They may also recommend other vaccines, such as Shingrix^® for shingles. These all help reduce your risk of serious illness from these infections. Most people can have these vaccines, including people with weak immune systems.

You should not have live vaccines if your immune system is weak. This includes if you are having or recently had chemotherapy, radiotherapy or other cancer treatments that affect your immune system. Live vaccines can make you unwell because they contain a very weak version of the illness they protect you against. There are several live vaccines, including the yellow fever vaccine.

It is important to ask your doctor, nurse or pharmacist for advice about having vaccinations. They can explain what vaccines are right for you and when it is best to have them.

Your doctor, nurse or pharmacist will advise you not to get pregnant or make someone pregnant while having this treatment and for some time afterwards. The drugs may harm a developing baby. It is important to use contraception to prevent pregnancy. Follow their advice about:

• what types of contraception to use 
• how long after treatment you should continue to use contraception. 

You are advised not to breastfeed while having this treatment, or for some time after treatment ends. This is because the drugs could be passed to the baby through breast milk. 

Your doctor, nurse or pharmacist can give you more information.

Some cancer drugs can affect whether you can get pregnant or make someone pregnant. If you are worried about this, it is important to talk with your doctor before you start treatment.

If you need medical treatment for any reason other than cancer, always tell the healthcare professional that you are having cancer treatment. Give them the contact details for your cancer doctor or cancer team so they can ask for advice.

If you have appointments with a dentist, always tell them you are having cancer treatment. Talk to your cancer team before you have any dental treatment.