What is Ibrance® (palbociclib)?

Reviewed by: HU Medical Review Board | Last reviewed: June 2023

Ibrance is an oral targeted therapy. It is used to treat people with advanced or metastatic breast cancer that is hormone receptor-positive and human epidermal growth factor receptor 2 (HER2) negative. It is used in combination with certain hormone therapies.1

What is the ingredient in Ibrance?

The active ingredient in Ibrance is palbociclib.1

How does palbociclib work?

Palbociclib is a type of drug known as a kinase inhibitor. These drugs block certain proteins that control cellular functions like signaling, cell division, and survival. Palbociclib is a CDK 4/6 inhibitor. CDK4 and CDK6 are proteins that are important during a cell’s growth cycles. In cancer cells, CDK4 and CDK6 may be overactive, which may cause the cancer cells to grow uncontrollably. By blocking CDK4/6, palbociclib can help slow the growth of breast cancer cells. However, it may also interfere with the normal growth of healthy cells.1,2

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Hormone receptor-positive breast cancer cells are stimulated by the presence of hormones like estrogen. This can increase the activity of CDK4/6. Palbociclib is used along with certain hormone therapies to work against cancer cells in 2 ways:1,3

  • Blocking the hormone receptors (hormone therapy)
  • Blocking the enzymes CDK4/6 (palbociclib)

In clinical trials, the combination of hormone therapy and palbociclib was more effective in slowing tumor growth than either of these treatments alone.1,3

What are the possible side effects of palbociclib?

The most common side effects of palbociclib include:1

  • Infections
  • Fatigue
  • Nausea, vomiting
  • Mouth sores and swelling
  • Anemia (lowered red blood cell counts)
  • Hair loss
  • Diarrhea
  • Lowered platelet levels
  • Rash
  • Decreased appetite
  • Weakness
  • Fever

Palbociclib may also cause serious side effects, including:1

  • Low white blood cell counts (neutropenia) – Not having enough white blood cells can put you at risk for infections. Your doctor should check your white blood cell counts before and during treatment.
  • Lung problems (pneumonitis) – Tell your doctor right away if you have new or worsening signs of lung problems. This includes trouble breathing, shortness of breath, cough, and chest pain.

These are not all the possible side effects of palbociclib. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment with palbociclib.

Things to know about palbociclib

Do not eat grapefruit or drink grapefruit juice during treatment with palbociclib. These products may increase the levels of palbociclib in the body, which can increase the potential for side effects.1,3

Before taking palbociclib, tell your doctor if you have:1,3

  • Fever, chills, or other signs of an infection
  • Liver problems
  • Kidney problems

Palbociclib can harm an unborn baby. If you or your partner can become pregnant, you should use birth control during treatment and for some time after the last dose of palbociclib. You should also not breastfeed during treatment with palbociclib and for some time after the last dose. Talk to your doctor about your options for birth control and breastfeeding while taking palbociclib.1,3

Before beginning treatment for breast cancer, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you are taking. This includes over-the-counter drugs.

For more information, read the full prescribing information of palbociclib.