Abemaciclib (Verzenios)

Abemaciclib is a targeted therapy drug. 

Abemaciclib belongs to a group of drugs called CDK4/6 (cyclin dependent kinase) inhibitors. These drugs block the action of kinase, which is a protein that helps cells to grow and divide. This stops the growth and spread of cancer.

Abemaciclib is the drug’s non-branded name. You may hear it called by its brand name Verzenios.

Abemaciclib is used to treat breast cancer that is oestrogen receptor positive (ER-positive) and HER2-negative. Men and women can both take it.

You may be offered abemaciclib if you have: 

• Primary breast cancer that your treatment team think has a higher risk of coming back (recurrence). If you have abemaciclib after surgery, it’s called adjuvant treatment
• Locally advanced breast cancer
• Metastatic (secondary) breast cancer

You take abemaciclib as a tablet twice a day. The usual dose of abemaciclib is 300mg, taken as two 150mg tablets. 

You must take your tablets:

• About the same times each day, about 12 hours apart
• Whole with water (do not crush, chew or dissolve them)

You can take them with or without food.

Abemaciclib and hormone therapy

Abemaciclib is always given alongside a hormone therapy drug to treat breast cancer.

The hormone therapy drug you take will depend on whether you’ve been prescribed abemaciclib for primary breast cancer or for locally advanced or metastatic breast cancer.

Abemaciclib for primary breast cancer

If you’re prescribed abemaciclib after surgery for primary breast cancer, you may have it with: 

• An aromatase inhibitor (anastrozole, exemestane or letrozole)
• Tamoxifen

The drug that’s recommended will depend on your circumstances.

If you have not been through the menopause

If you have not been through the menopause (when your periods stop), you may also have treatment to stop your ovaries producing oestrogen, either temporarily or permanently. This is called ovarian suppression. Your treatment team will talk to you about this.

If you’re a man

Men who are prescribed abemaciclib for primary breast cancer will usually have it with tamoxifen. Or they may be given an aromatase inhibitor with an injection to suppress their testosterone production.

Abemaciclib for locally advanced or metastatic breast cancer

If you’re prescribed abemaciclib for locally advanced or metastatic breast cancer you may have it with:

• An aromatase inhibitor (if you have not already had hormone therapy for locally advanced or metastatic breast cancer)
• Fulvestrant (if you have had an aromatase inhibitor for locally advanced or metastatic breast cancer)

If you have not had hormone therapy for locally advanced or metastatic breast cancer but you did have hormone therapy for primary breast cancer, you may be offered either of these drugs alongside abemaciclib. The drug that’s recommended will depend on your circumstances.

Abemaciclib is offered in the same way to both men and women with locally advanced or metastatic breast cancer.

You may be prescribed abemaciclib if you have not been through the menopause (are premenopausal). If this is the case, you may have abemaciclib with another drug, to stop your ovaries producing oestrogen (ovarian suppression). Your treatment team will talk to you about this.

Taking abemaciclib with an aromatase inhibitor

Aromatase inhibitors are tablets taken once a day.

Taking abemaciclib with fulvestrant

Fulvestrant is given in 2 injections, 1 in each buttock. These are known as intramuscular injections. They are usually given every 2 weeks for the first 3 doses, then every 4 weeks for as long as you’re having abemaciclib. 

Taking abemaciclib with tamoxifen

Tamoxifen is a tablet taken once a day.

What if I miss a dose?

If you miss a dose of abemaciclib, or you’re sick (vomit) soon after taking it, do not take an extra dose to make up for the one you missed.

Take the next dose at your usual time and speak to someone in your treatment team.

How long will I take abemaciclib for?

If you have primary breast cancer, you’ll usually take abemaciclib for 2 years alongside hormone therapy. After this you’ll stop taking abemaciclib, but you’ll continue to have hormone therapy for a total of 5 or 10 years.

If you have locally advanced or metastatic breast cancer, you’ll have abemaciclib alongside hormone therapy for as long as your treatment team feels you’re benefiting from the treatment and any side effects are manageable.

Like any treatment, abemaciclib can cause side effects. Everyone reacts differently to drugs and some people have more side effects than others. These side effects can usually be managed and those described here will not affect everyone. 

As abemaciclib is given with hormone therapy, it’s sometimes difficult to know which side effects are being caused by which treatment. 

If you’re worried about any side effects, regardless of whether they’re listed here, talk to your treatment team. 

Common side effects of abemaciclib include:

• Effects on the blood
• Diarrhoea
• Liver changes
• Extreme tiredness (cancer-related fatigue)
• Nausea and vomiting
• Loss of appetite
• Change in taste
• Skin changes
• Hair thinning and hair loss
• Sore mouth

Effects on the blood 

Abemaciclib can temporarily affect the number of blood cells in the body. Blood is made up of red cells, white cells and platelets. 

You’ll have regular blood tests. If these show the number of blood cells is too low, your next treatment may be delayed.

Your treatment team may change the dose of a drug to suit you and help manage its side effects. This may help you stay on the treatment for longer. 

Risk of infection 

Not having enough white blood cells can increase your risk of getting an infection. 

Before starting abemaciclib, you should be given a 24-hour contact number or told who to contact if you feel unwell at any time during your treatment, including overnight or at the weekends.

You may need treatment if you get an infection.

Sometimes your treatment team may recommend injections of drugs called growth factors. This helps the body make more white blood cells to reduce your risk of infection.

Anaemia 

Having too few red blood cells is called anaemia. If you feel breathless, dizzy or particularly tired, let your treatment team know.

Bruising and bleeding 

Abemaciclib can reduce the number of platelets. Platelets help the blood to clot.

If your platelets are low, you may: 

• Bruise more easily 
• Have nosebleeds 
• Notice that your gums bleed when you brush your teeth 
• Take longer to stop bleeding if you cut yourself 

Tell your treatment team if you have any of these symptoms. 

Diarrhoea

Diarrhoea is a very common side effect of abemaciclib and can sometimes be severe. 

You’re most likely to have severe diarrhoea in the first month of treatment.

Your treatment team will prescribe anti-diarrhoea medicine so you have it available at home before you start your treatment. If you get diarrhoea, you should start the anti-diarrhoea medicine straight away. Make sure to drink plenty of fluids.

If the diarrhoea continues despite the anti-diarrhoea medicine, or you have diarrhoea 3 or more times in 24 hours, compared to what’s usual to you, contact your treatment team.

Reducing the amount of fibre that you eat can sometimes help with diarrhoea, but speak with your treatment team before making any changes to your diet.

If you develop severe diarrhoea while taking abemaciclib, your doctor may reduce the dose, delay your next cycle of treatment or stop your treatment completely.

Liver changes

Abemaciclib can affect how the liver works. This does not usually cause any symptoms.

You’ll have blood tests to check your liver enzyme levels during treatment. Treatment may need to be delayed or the dose reduced if the blood tests show any problems with your liver. Liver enzyme levels usually return to normal once treatment is paused or stopped.

Extreme tiredness (cancer-related fatigue) 

Fatigue is extreme tiredness that does not go away with rest or sleep.

Fatigue is a common side effect of abemaciclib and may last for weeks or months after your treatment has finished.

Fatigue may affect how you cope with your cancer and its treatment. It can also make everyday activities harder and affect your quality of life. 

If you think you have fatigue, tell your GP or treatment team. They can assess you and offer advice on how to manage your energy levels. 

Find out more about managing fatigue.

Nausea and vomiting

You may feel sick (nausea) or be sick (vomit). Your treatment team can prescribe anti-sickness drugs to help with this if needed. Contact your treatment team if you’re sick 3 or more times in 24 hours or are finding it difficult to eat and drink.

Loss of appetite

You may not feel like eating, especially if you feel sick. It might help to eat small meals regularly and drink plenty of liquids.

Change in taste

Your sense of taste may change and some food may taste different, for example more salty, bitter or metallic. 

It can help to try different types of food to see what tastes best to you.

Skin changes

You might get a rash anywhere on your body.

You may also have dry skin. You may notice your skin is scaly, rough, tight or itchy.

Your treatment team may suggest drugs such as antihistamines to reduce any itching.

It may also help to:

• Use a moisturiser regularly and avoid perfumed products
• Use high factor sunscreen when out in the sun
• Protect your hands when doing household or outdoor chores
• Rinse and dry your hands carefully, particularly after contact with cleaning products
• Pat your skin dry with a soft towel, rather than rubbing vigorously
• Take care when shaving
• Wear clothing made of natural fibres (such as cotton) where possible and wash clothes in mild detergent

Hair thinning and hair loss

Taking abemaciclib and hormone therapy can cause hair thinning or hair loss.

Find out more about hair loss. 

Sore mouth 

Looking after your mouth, including your teeth and gums, is very important during treatment.

You may be given mouthwash to try to reduce soreness and prevent mouth ulcers developing. It’s a good idea to use a small, soft toothbrush during this time.

See your dentist for a check-up before treatment begins. Avoid dental work during these treatments if possible.

If you do need to have dental work during treatment, talk with your treatment team about the best time to have this. 

If you’re having difficulty registering with a dentist, let your treatment team know.

Other common side effects

Other common side effects include:

• Dizziness
• Headaches

Your treatment team can advise you on how to manage these.

Damage to the lungs (interstitial lung disease)

Abemaciclib can cause interstitial lung disease (ILD). ILD can cause inflammation in your lungs, which can lead to scarring.

If abemaciclib has caused inflammation to your lungs, you may need to stop treatment temporarily to prevent further damage. You may have steroids to treat the inflammation.

Contact your treatment team straight away if you have:

• Shortness of breath 
• A cough, with or without a high temperature 
• Any new or worsening breathing problems, such as chest tightness or wheezing 

These symptoms could have a number of causes including side effects of treatment or a lung infection. It’s important to let your treatment team know so that they can find out the cause. You may need a chest x-ray or CT scan to check what’s causing your symptoms.  

Other less common side effects

Other less common side effects include:

• Watery eyes
• Muscle weakness
• Indigestion
• Changes to your nails

Your treatment team can advise you on how to manage these.

Blood clots

People with breast cancer have a higher risk of blood clots. Having abemaciclib also increases the risk of blood clots such as a DVT (deep vein thrombosis). 

If you have a DVT, there’s a risk part of the blood clot could break away and travel to the lung. This is known as a pulmonary embolism (PE).

Blood clots can be life-threatening and should be treated quickly. 

Heart attack and stroke

Abemaciclib, when given with hormone treatment for metastatic breast cancer, has the potential to increase the risk of heart attack or stroke. It may not be suitable for people with existing heart conditions. Your treatment team will talk to you about this.

Medicines and food to avoid when taking abemaciclib

When taking abemaciclib:

• Do not take supplements containing St John’s Wort
• Do not eat grapefruit or drink grapefruit juice

Some drugs should not be taken with abemaciclib. These include some commonly prescribed antibiotics, antifungal, antiviral and anti-epileptic drugs. 

Tell your treatment team about any prescribed or over-the-counter medicines you’re taking, especially medicine that contains ketoconazole. This might include antifungal creams, gels or shampoos used to treat skin infections such as athlete’s foot. 

If a healthcare professional, such as your GP or dentist, prescribes you a new drug, tell them you’re taking abemaciclib.

Always ask your treatment team before taking any herbal medicines or supplements.

Abemaciclib contains lactose. If you’re lactose intolerant, discuss this with your treatment team.

Sex, contraception and pregnancy

You can still have sex during treatment. It’s thought some drugs used to treat breast cancer cannot pass into vaginal fluids or semen, but this cannot be completely ruled out. 

Most treatment teams will advise using barrier methods of contraception, such as condoms or female condoms, during treatment and for at least 3 weeks after your last dose.

You’re advised not to become pregnant while having treatment because abemaciclib can harm a developing baby. If you have not been through the menopause, talk to your team about the most suitable method of contraception for you. It’s still possible to become pregnant even if your periods are irregular or have stopped naturally or because of treatment for breast cancer.

Fertility

If you’re a woman 

It’s not known if abemaciclib affects fertility in women.

Conversations about fertility can be hard. It’s important to discuss any fertility concerns with your treatment team before you begin your treatment. They will be able to talk to you about fertility preservation options.

If you’re a man

Abemaciclib may affect fertility in men. You may want to talk to your treatment team about sperm preservation before starting treatment.

Abemaciclib and breastfeeding

You’ll be advised not to breastfeed during treatment and for at least 3 weeks after your last dose of abemaciclib. This is because there’s a risk the drug could be passed on through your breast milk.

Vaccinations and travel

If you’re planning a holiday or need to travel overseas, check with your treatment team first. 

You should not have any live vaccines while you’re having treatment.

For more information about vaccines, including COVID-19 and flu vaccines, see our information on vaccines and breast cancer.

Being diagnosed with breast cancer can make you feel lonely and isolated. But there’s support available. And you might find it helpful to talk to someone who knows what it’s like. 

You can call our helpline to speak to one of our nurses if you’ve got any questions or worries. See the bottom of this page for ways to get in touch.

And you can join our online forum to speak to others who are having similar treatment to you.

If you’ve been diagnosed with primary breast cancer, our Someone Like Me service will match you with a trained volunteer who’s had a similar experience to you. They'll be a phone call or email away to answer your questions, offer support or simply listen. Because there’s nothing like finding someone who really understands.

And our Living with Secondary Breast Cancer groups let you share experiences with other people who are also dealing with the uncertainty and challenges of metastatic breast cancer.