How Verzenio Works for Metastatic Breast Cancer

Written by Dena Westphalen, PharmD
Medically Reviewed by Shawn Bookwalter, BCPS, MSHI, MS, PharmD on September 22, 2026

Verzenio (abemaciclib) is a medicine that is used for certain types of breast cancer. It is used to treat breast cancer that is hormone receptor (HR)-positive and human epidermal growth factor receptor 2 (HER2)-negative. It can be used to treat early breast cancer or breast cancer that is advanced or has spread to other parts of the body (metastatic). It may also be used for advanced or metastatic breast cancer with a specific gene change called an ESR1 mutation in certain people. This article will focus on Verzenio treating metastatic breast cancer. 

Verzenio is a type of medicine called a kinase inhibitor. Kinases are enzymes in the body that can send and receive signals to help your cells do important functions. Verzenio blocks the action of cyclin-dependent kinases 4 and 6 (CDK4 and CDK6). Kinases CDK4 and CDK6 send signals to help cancer cells grow and multiply. Verzenio blocks the activity of CDK4 and CDK6 to help stop cancer cells from growing and multiplying and to make tumors shrink in size. 

Metastatic breast cancer that is hormone receptor (HR)-positive and human epidermal growth factor receptor 2 (HER2)-negative may be treated by Verzenio. Metastatic breast cancer means the cancer has spread to other parts of the body. The cancer may or may not have been previously treated with hormone therapy. Verzenio is usually used along with another medicine. It may also be used alone to treat breast cancer that has progressed after both hormone therapy and chemotherapy after the cancer has spread.

Verzenio may also be used for advanced or metastatic breast cancer that has a specific gene change called an ESR1 mutation, in people whose cancer kept growing after at least one hormone therapy.

Verzenio is taken as a tablet that you will swallow. You will usually take Verzenio twice a day, and you can take it with or without food. You should try to take your Verzenio doses around the same times every day. Verzenio should be taken whole, and you should not crush or chew the tablets. Do not take tablets that are broken, cracked, or damaged, and you should contact your pharmacy about getting damaged tablets replaced. If you vomit after taking a dose of Verzenio, skip the dose and do not take an extra dose. Take your next Verzenio dose as scheduled. 

You will continue taking Verzenio for as long as possible. This means you will take it until your cancer progresses or you have side effects that make it not safe for you to take. If you have certain side effects, your health care provider may change or pause your doses of Verzenio. In some cases, they may need to have you stop taking Verzenio completely.

The FDA approved Verzenio for HR-positive, HER2-negative metastatic breast cancer based on clinical trials that looked at how effective Verzenio was for treating the cancer. It was first approved by the FDA in 2017.

In the MONARCH 3 clinical trial, people took either Verzenio combined with a hormone therapy called an aromatase inhibitor or a placebo with an aromatase inhibitor for HR-positive, HER2-negative metastatic breast cancer that had no prior treatment for metastatic disease. A placebo is used in clinical trials as a control so that the potential benefit of a medicine in a group of people can be compared in a similar group of people who did not receive a medicine. An aromatase inhibitor works to block estrogen in the body. In this clinical trial, either anastrozole or letrozole was used as the aromatase inhibitor medicine.

  • The clinical trial included 493 people, with 328 people taking Verzenio. 
  • In this study, 58% people were White, 30% were Asian, 1.6% were Black or African American, 1.4% were American Indian or Alaska Native, 0.2% were Native Hawaiian or Other Pacific Islander, 0.4% were multiple races, and race was not reported for 7.9%. 
  • Participants were followed to see how long it took for their breast cancer to progress, meaning that the cancer grew or spread. This measurement is called progression-free survival. 
  • The median progression-free survival was 28.2 months for Verzenio plus an aromatase inhibitor, compared to 14.8 months for a placebo plus an aromatase inhibitor. This means that half of the people who took Verzenio did not have their cancer progress for at least 28.2 months, compared to 14.8 months for people who took the placebo.

In the MONARCH 2 clinical trial, people took either Verzenio combined with a hormone therapy called fulvestrant or a placebo with fulvestrant for HR-positive, HER2-negative metastatic breast cancer that had not been treated with chemotherapy for metastatic disease but did previously have treatment with hormone therapy. Fulvestrant works to block estrogen in the body.

  • The clinical trial included 669 people, with 446 people taking Verzenio. 
  • In this study, 56% of people were White, 32% were Asian, 3.9% were American Indian or Alaska Native, 2.1% were Black or African American, and race was not reported for 6.3%. 
  • The median progression-free survival was 16.4 months for Verzenio plus fulvestrant, compared to 9.3 months for the placebo plus fulvestrant. This means that half of the people who took Verzenio did not have their cancer progress for at least 16.4 months compared to 9.3 months for people who took placebo.

In the MONARCH 1 clinical trial, people took Verzenio for HR-positive, HER2-negative metastatic breast cancer that had been previously treated with hormone therapy and one to two chemotherapy regimens while it was metastatic. Verzenio was not compared against any other medicine. 

  • The clinical trial included 132 people who took Verzenio. In this study, 85% of people were White, 4.5% were Black or African American, 1.5% were Asian, and race was not reported for 9.1%. 
  • When the results were independently reviewed, 17% of people had either a complete or partial response to the medicine. This means that their tumor either went away (complete response) or significantly shrank in size (partial response). 
  • The median duration of response was 7.2 months. This means that half of the people who had a response had their tumors continue responding for at least 7.2 months. 

In 2026, the FDA approved Verzenio in combination with imlunestrant for advanced or metastatic breast cancer that is estrogen receptor (ER)-positive, HER2-negative, and has a specific gene change called an ESR1 mutation. ER-positive means the cancer grows in response to the hormone estrogen. ESR1 is a gene found in some cancer cells. When these gene has a change (mutation), the cancer may keep growing even when estrogen is blocked by hormone therapy. A blood test approved by the FDA can check if your cancer has this gene change.

  • The clinical trial that led to this approval was called EMBER-3. In EMBER-3, people whose cancer had kept growing after using at least one hormone therapy took either Verzenio plus imlunestrant or imlunestrant alone. Imlunestrant is a hormone therapy that works to block estrogen in the body. All people in the study were tested for the ESR1 mutation using a blood test approved by the FDA.
  • The study looked at 159 people with the ESR1 mutation, with 67 taking Verzenio plus imlunestrant and 92 taking imlunestrant alone. In this study, 60% of people were White, 27% were Asian, 5% were Black, 0.6% were American Indian or Alaskan Native, 0.6% were multiple races, and 7% had race missing. 
  • The median progression-free survival was 11.1 months for Verzenio plus imlunestrant, compared to 5.5 months for imlunestrant alone. This means that half of the people who took Verzenio did not have their cancer progress for at least 11.1 months, compared to 5.5 months for people who took imlunestrant alone.

Your results may differ from what was seen in clinical studies. 

Verzenio will start working as soon as you start taking it. Your health care provider will usually do a scan to see how your cancer is responding to the treatment 6 weeks after you start your medicine. They may choose to do the scan earlier or later than 6 weeks. 

Your health care provider will also do regular bloodwork to monitor how Verzenio is working in your body. These tests will monitor your blood counts, such as white blood cells, neutrophils, and platelets, so that your health care provider knows that you can continue to take Verzenio safely. If you have certain side effects, such as a cough, your health care provider may do more tests to make sure it is safe for you to continue to take Verzenio. 

Side effects are common with medicines that treat cancer, including Verzenio. It is important to tell your health care provider about any side effects you have while you’re taking Verzenio or after. They can help to find out if your side effects are serious or provide more information to help you manage the side effects.

Your health care provider will have you do bloodwork regularly while taking Verzenio. It’s important to go to all of your bloodwork appointments so that your health care provider can make sure Verzenio is safe for you. These tests will make sure you do not have any problems with your blood cell counts that make it unsafe for you to take Verzenio. This is because Verzenio can cause low white blood cell counts, also called neutropenia. If not treated, neutropenia can cause serious infections that can be dangerous and even life-threatening.

You can ask your health care provider what else you can do to prevent or treat common side effects. For example, you can help to prevent and treat nausea, vomiting, and diarrhea by eating bland foods and having multiple small meals throughout the day instead of three large meals. They may also recommend you keep certain over-the-counter medicines on hand to treat common side effects like diarrhea and let you know what to do if you have severe diarrhea. They will also tell you how to watch for severe side effects, such as lung problems or blood clots, and what to do if you have these side effects.

If you have certain side effects while you take Verzenio, your health care provider may need to change your dose of medicine, pause your doses, or even stop your medicine altogether. This will depend on the side effect you have, how severe it is, and what treatment it needs. If your Verzenio dose needs to be lowered, the medicine will continue to work in your body. If your medicine is paused, it is possible that your health care provider will restart the medication at the same dose or at a lower dose once your side effect is treated and gets better.

While taking Verzenio, you will need to avoid grapefruit. You should not eat grapefruit or drink any juice that has grapefruit. This is because grapefruit can block your body’s ability to break down (metabolize) Verzenio, causing too much of the medicine to stay in your body and increasing your risk of side effects. 

While taking Verzenio, you should not take ketoconazole, an antifungal medicine that is used to treat some infections. It can cause too much Verzenio to stay in your body and increase your risk of dangerous side effects. 

If you are taking certain medications, your dose of Verzenio may need to be lowered. Tell your health care provider about all medications and supplements you are taking or plan to take while taking Verzenio. They will help to tell you how to take Verzenio so it can be safe and effective for treating your cancer. 

If you have certain health conditions, such as liver problems, your dose of Verzenio may need to be changed to once daily. Do not change your dose on your own. Talk with your health care provider about your health history so they can decide what dosage is right for you.

The maker of Verzenio has a financial assistance program and may be able to offer coupons or savings for Verzenio. 

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