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CemiplimabĀ A1199

Information leaflet on Cemiplimab A1199

This leaflet provides information for patients having treatment with cemiplimab.  The leaflet will explain what cemiplimab is and when and how it is given.  It will also tell you about common side effects that you may experience.  Contact telephone numbers and details of how to obtain further information on cemiplimab are given at the end of the leaflet.

What is cemiplimab and why am I having it?

Cemiplimab is a treatment which helps your immune system to attack and destroy cancer cells. It is an immunotherapy drug, it is not a chemotherapy drug.  

How often will I receive cemiplimab?

For this treatment to be most effective, it is given at specific time intervals.  Cemiplimab is given once every 3 weeks. Your doctor will discuss with you how long you will have to continue having the treatment.

How often will I see the specialist team?

You will need to be seen in the outpatient clinic before each treatment.  At each outpatient clinic the team who prescribes your cemiplimab will check how you are feeling and discuss any problems you may have.

You will have regular blood tests.  This is so we can check how the treatment is affecting you.  If your blood results are satisfactory, your treatment will be given.

How is cemiplimab given?

Cemiplimab is given through a drip into a vein in the back of your hand or arm.

Where will my treatment be given?

The treatments will be given in the day case treatment areas at Velindre.

How long will I be in the hospital?

You will need to allow between 1 -2 hours for your treatment appointment.

Can I bring relatives and friends with me? 

You are welcome to bring someone to stay with you during your treatment. Space is limited so there is not usually room for more than one person.  Treatment areas are not suitable for young children.

Reactions during the treatment 

A small number of people may have a reaction at the time of their treatment. If you experience any of the following during the treatment please tell your nurse straight away:

  • Feeling hot and feverish
  • Chills or shivering
  • Headache
  • Dizziness or faintness
  • Problems with breathing
  • Rash
  • Feeling sick or vomiting

If any of these occur we will slow down or stop the cemiplimab until you feel better.  The treatment can then start again, usually without any further problems.

What are the possible side effects?

Some people have very few side effects whilst others may experience more.  Most of the side effects happen because Cemiplimab affects the immune system causing inflammation of other parts of the body such as your skin, bowels, lungs and hormone producing glands. Most, if not all severe side effects can be controlled by the use of steroid medication immediately either as tablets or through a drip.  Hospital admission may be needed for severe immune related reactions. 

Mostly side effects are mild and can be easily managed at home. But it is important that if you have more severe side effects that you contact Velindre Cancer Centre. The telephone number is at the end of the leaflet.  Further details of when to contact Velindre are included in the individual side effects listed below.

If you are admitted to another hospital, you must inform the doctors and the nurses that you are taking Cemiplimab.  It is possible you could be having an immune reaction and should be started on steroids. The doctors and nurses need to contact Velindre Cancer Centre for advice.  They can either telephone the treatment helpline or speak to your oncologist.

You will be given an alert card, please show this to the nurses or doctors if you are admitted to any hospital. 

Side effects may continue for up to 18 months after treatment. If you are admitted to hospital or see your GP during this period, inform the doctor you have had Cemiplimab, an immune therapy.

Sometimes cancer drugs can have very serious side effects which can be life threatening. It is important to inform Velindre cancer centre if you are concerned about any side-effects.

Effects on the bowels  

This treatment may cause diarrhoea.  
If you experience diarrhoea it is important that you drink plenty of fluids.  You will be given some medication to control diarrhoea please take these as instructed. 

Please note:
If you have any of the symptoms below you must inform Velindre Cancer Centre immediately, the telephone numbers are at the end of the leaflet. 

  • 4 or more bowel movements in 24 hours above what is normal for you.
  • if you have any problems with diarrhoea or an increase in bowel movements which lasts for more than 3 days.
  • If you have stomach pains with or without diarrhoea 
  • Or if you have blood or mucus in your bowel motions

There is a risk of inflammation of the bowel (colitis) or rupture of the bowel (perforation) in a small number of patients. 

Effects on the skin
You may develop an itching skin rash which can be treated with moisturising cream.  However if you get a severe skin reaction you may need to be treated in hospital. 

Please contact Velindre Cancer Centre if:

  • If the rash covers more than half of your body and is painful.
  • If you have large blisters or your skin is peeling.
  • If your skin feels very raw.
  • If you have itchy eyes.
  • If you have mouth ulcers.  

Effects on your hormone glands

Cemiplimab can cause inflammation of the glands that produce hormones (chemicals that control many of the body’s functions). Symptoms will vary depending on which glands are affected. Although it is rare it is possible that this may result in you developing diabetes. If your hormone glands are affected this may be a permanent problem but medication can be prescribed to replace the hormones if required. 

It is important to contact Velindre cancer Centre if you have the following: 

  • a headache that will not go away
  • nausea and vomiting
  • severe mood swings.
  • severe tiredness (mild to moderate tiredness is  common with cemiplimab) 
  • If you have a noticeable increase in energy levels or restlessness.
  • If you feel forgetful and/or confused

Effects on your lungs 

Cemiplimab may cause inflammation to your lungs. If you develop new problems with feeling short of breath or a dry cough please contact Velindre for advice. 

Effects on the liver

This is rare, but if you are affected you may feel more tired than usual and may also feel sick or vomit.  Your doctor will give you anti sickness medicine to take.  

Please contact Velindre Cancer Centre if:

  • If you vomit more than once in 24 hours despite taking anti sickness medication.

More severe effects on the liver are very rare but can be very serious so you should contact Velindre Cancer Centre if:

  • If you have yellowing of your skin and the whites of your eyes.
  • If you have darker urine than normal.
  • If you have unusual bruising or bleeding

Tiredness and fatigue 

Cemiplimab can make you feel more tired than usual.  It is important to listen to your body and rest if you need to, but carry out your normal activities if you feel able.  Some people find it beneficial to take gentle exercise as well as taking rest.  If you are sleeping more than 50% during the daytime you need to contact Velindre Cancer Centre on the treatment helpline. The telephone number is at the end of the leaflet.

Loss of appetite 

You may experience a loss of appetite and some people may feel sick whilst taking cemiplimab but this can usually be well controlled with anti sickness medication.  If you are sick more than once in 24 hours despite taking regular anti-sickness medicine, you should contact Velindre Cancer Centre for advice.  The telephone number is at the end of the leaflet.

Effects on the nerves

You may have numbness or tingling in your hands or feet.  

Please contact Velindre Cancer Centre if:

  • If numbness in your hands and feet is severe.
  • If you develop weakness in your arms or legs
  • If you become dizzy or giddy.
  • If you become very drowsy and have difficulty staying awake.

Myalgia (pain in the muscles)

Some patients may experience myalgia which is muscle or joint pain.   If you already have painkillers at home you may find they relieve the pain.  If this does not work please contact Velindre Cancer Centre.  The telephone number is at the end of the leaflet.


You are at an increased risk of picking up infections because your white blood cells which help fight infections can be reduced by this treatment.  Contact Velindre Cancer Centre immediately if you develop any signs of infection, for example flu like symptoms or a temperature above 37.5°centigrade.  The telephone number is at the end of the leaflet.

Hair loss

Cemiplimab should not make you lose your hair.  However, a small number of people may experience some hair thinning.  We have a leaflet that tells you more about coping with hair loss.  Please ask your nurse if you would like a copy.

Risk of blood clots: 

A diagnosis of cancer can increase your risk of developing a blood clot (thrombosis), and having cancer treatment may increase this risk further.  It is important to tell your doctor immediately if you have symptoms such as pain, redness and swelling in your leg, or breathlessness and chest pain.  

Blood clots can be very serious.  However, most clots can usually be successfully treated with drugs to thin the blood.  Your doctor or nurse can give you more information.

Other side effects: 

You may have these additional side effects, if so please contact Velindre Cancer Centre:

  • Increased frequency of passing urine and/or thirst.
  • Dizziness or light headedness.
  • Decreased urine output.
  • Blurred vision or red sore eyes.

Other information

It is important you do not become pregnant, breastfeed or father a child whilst having cemiplimab treatment and for a year after treatment.  

Manufacturer’s patient information leaflets

Velindre leaflets provide information about very common and commonly reported side-effects (we are unable to list all of the common side effects), for more information regarding these and the less common side-effects please refer to the manufacturers patient information leaflets, obtained from Velindre pharmacy and/or on the internet at Sometimes patients may find these leaflets difficult to read however. Please ask if you would like a copy from your doctor or from Velindre pharmacy

Contact telephone numbers

Velindre Cancer Centre 029 2061 5888
If you are unwell at home and need immediate advice at any time of the day or night ask for the treatment helpline

Pharmacy department 029 2061 5888 ext 6223
Monday – Friday 9am – 5pm for queries about your medicines

Macmillan freephone Helpline 0808 808 0000

Tenovus freephone 0808 808 1010
cancer helpline 

This information is also available in Welsh

This leaflet was written by health professionals.  The information contained in this leaflet is evidence based.  The leaflet has been approved by doctors, nurses, pharmacists and patients.  It is reviewed and updated every 2 years.

Prepared November 2019