How effective is Ibrance?

Key Points

• In clinical studies of Ibrance plus letrozole, patients with HR+, HER2- advanced or metastatic breast cancer saw a significant delay of disease progression of a median of 24.8 months versus 14.5 months for those that received letrozole and placebo.
• In clinical studies of Ibrance plus fulvestrant, a delay of disease progression was demonstrated for a median of 9.5 months compared to 4.6 months for the group that took fulvestrant plus placebo.
• A reduction in tumor size was also seen in each group.

Ibrance (generic name: palbociclib), from Pfizer, is an oral treatment used in adults to treat hormone-receptor-positive, HER2-negative breast cancer that is advanced or has spread in the body (metastatic).

• It is used in combination with an oral hormonal therapy called an aromatase inhibitor for postmenopausal women or men who have not been treated with hormonal therapy before.
• It is also approved for use in combination with fulvestrant intramuscular injection for those whose disease worsens after using an aromatase inhibitor.
• Women who have not reached menopause are treated with Ibrance plus fulvestrant therapy and a luteinizing hormone-releasing hormone (LHRH) agonist to suppress ovarian function.

Aromatase inhibitors include medicines such as anastrozole (Arimidex), exemestane (Aromasin), and letrozole (Femara). Fulvestrant (Faslodex) is considered an estrogen receptor antagonist.

Effectiveness of Ibrance plus an aromatase inhibitor

• In a Phase 3 clinical study of 666 postmenopausal women with HR+/HER2- metastatic breast cancer who had not received prior hormone therapy for their metastatic disease, the combination of Ibrance and letrozole significantly delayed the progression of their disease for a median time of 24.8 months versus 14.5 months for those that received letrozole and placebo (an inactive treatment).
• Patients taking Ibrance with letrozole reduced their risk of disease progression by 42% compared to those taking letrozole and placebo.
• For patients taking Ibrance plus letrozole, over half (55%) saw their tumor size shrink compared to about 44% of those who took letrozole and placebo.

Effectiveness of Ibrance plus fulvestrant

• Ibrance plus fulvestrant was compared to Ibrance plus placebo in a Phase 3 clinical trial of 521 women with HR+/HER2- metastatic breast cancer, regardless of their menopausal state. These women had already received hormone therapy for breast cancer (early stage or metastatic).
• The group who received Ibrance plus fulvestrant had a delay in disease progression for a median of 9.5 months compared to 4.6 months for the group that took fulvestrant plus placebo. Patients taking Ibrance with fulvestrant reduced their risk of disease progression by 54% compared to those taking fulvestrant and placebo.
• For patients taking Ibrance plus fulvestrant, about 25% saw their tumor size shrink compared to about 11% who took fulvestrant and placebo.

How does Ibrance work in breast cancer?

Ibrance is considered a cyclin-dependent kinase (CDK) 4/6 inhibitor. Some cancer cells have proteins like CDK that promote rapid growth. Ibrance blocks the CDK4 and CDK6 proteins in the cell to help slow down cell division that leads to cancer. Your doctor can test you to see if you have the kind of cancer that would respond to "targeted" drug therapy like Ibrance.

Hormones can fuel some breast cancers known as estrogen receptor (ER) positive cancers and/or progesterone receptor positive (PR+) cancer. About 70-80% of all diagnosed breast cancers are hormone receptor-positive. These cancers may be treated with medicines known as hormone therapy (aromatase inhibitors), which block estrogen or prevent production. Ibrance is also used with the estrogen receptor antagonist fulvestrant in those with disease progression following hormone therapy.

Women who have not reached menopause are treated with Ibrance plus fulvestrant therapy and a luteinizing hormone-releasing hormone (LHRH) agonist to suppress ovarian function.

How do I take Ibrance?

The recommended starting dose of Ibrance is 125 mg. Always follow your doctor’s specific direction for Ibrance dosing.

If you are taking Ibrance plus an aromatase inhibitor:

When taking Ibrance with an aromatase inhibitor, you take the pills in a 28-day cycle.

• You take one Ibrance plus one aromatase inhibitor each day for 21 days. Then you take the aromatase inhibitor alone (without Ibrance) for 7 days.
• You continue this 28-day cycle of medicines as long as you are getting a benefit and not having bothersome side effects.

If you are taking Ibrance plus fulvestrant:

When taking Ibrance with fulvestrant (Faslodex) injection, the pills are also taken in a 28-day cycle.

• You take Ibrance at the same time each day for 21 days, then you stop for 7 days.
• You will also receive fulvestrant intramuscular (IM) injection 500 mg every 2 weeks for the first three injections (one dose on days 1, 15, and 29 of the first month) and then one injection every 4 weeks thereafter.
• Women who have not reached menopause are treated with Ibrance plus fulvestrant therapy and a luteinizing hormone-releasing hormone (LHRH) agonist to suppress ovarian function.

Does Ibrance come as a tablet?

Yes, Ibrance is now available as a tablet, and can be taken with or without food. Ibrance capsules should be taken with food.

Eventually Ibrance will only be available as a tablet. Swallow the Ibrance tablet whole. Do not chew, crush, or split the tablets before swallowing them.

Ibrance tablets and capsules are both available in a 125 mg, 100 mg, and 75 mg strength.

Common side effects

• Low red blood cell counts and low platelet counts
• Infections
• Feeling tired
• Nausea and vomiting
• Hair loss
• Mouth sores
• Liver test changes
• Loss of appetite
• Rash

Bottom Line

• Ibrance is effective in delaying disease progression for over 2 years when used with letrozole in metastatic breast cancer patients who have not been treated with hormonal therapy before.
• Ibrance plus fulvestrant more than doubled the median time until disease progression (9.5 months) when compared to fulvestrant plus placebo (4.6 months) in women who had already received hormone therapy for breast cancer.
• Tumor response to treatment was also measured. Tumor size was reduced in both the letrozole plus Ibrance and fulvestrant plus Ibrance groups.