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How does Ibrance kill cancer?

Medically reviewed by Carmen Fookes, BPharm. Last updated on June 27, 2022.

Official answer

  • Ibrance targets two particular enzymes CDK4 and CDK6, that are important for cell division.
  • In some cancers, such as HR-positive, HER2-negative breast cancer, CDK4/6 activity is overactive and out of control in breast cancer cells.
  • By inhibiting these enzymes, Ibrance slows down cell division that leads to new cancer growth.

Ibrance (palbociclib) is a targeted treatment that helps to reduce the growth and spread of cancer cells in the body. Ibrance may be used to treat advanced or metastatic breast cancer in women with HR-positive, HER2-negative disease and is usually given when cancer has progressed or spread to other parts of the body despite other treatments.

How does Ibrance work in breast cancer?

Ibrance belongs to the class of medicines known as CDK 4/6 inhibitors.

CDK4/6 inhibitors, such as Ibrance, target particular enzymes, called CDK4 and CDK6. CDK stands for cyclin-dependent kinase, and it is an enzyme that is important for cell division. By blocking these enzymes Ibrance slows down cell division that leads to new cancer cell growth.

Some cancers, such as hormone-receptor-positive breast cancer, are more likely to have overactive and unregulated CDK4/6 activity, and CDK 4/6 inhibitors such as Ibrance are useful for treatment.

Research suggests CDK4/6 inhibitors, such as Ibrance, may increase the time people have before cancer spreads. More evidence is needed to determine their impact on overall survival.

Ibrance is normally given for 21 days in a row along with other medications, such as an aromatase inhibitor or fulvestrant. This cycle is repeated every 28 days as long as you are having a positive response to the medicine and tolerate the side effects well.


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