Palbociclib

Palbociclib (brand name Ibrance) is used to treat certain types of HR-positive/HER2-negative and HR-positive/HER2-positive breast cancers in adults. It is an oral capsule/tablet taken once daily. Palbociclib is not chemotherapy; it is a targeted treatment.

Palbociclib is a kinase inhibitor, specifically a CDK 4/6 inhibitor. Palbociclib works by blocking two proteins, CDK4 and CDK6, that cancer cells need to grow and divide. Blocking these proteins prevents cancer cells from dividing further, which slows or stops tumor growth. Palbociclib is usually combined with other treatments, such as an aromatase inhibitor, fulvestrant, or trastuzumab, which block cancer growth signals in other ways. Used together, they are more effective at controlling cancer cell growth than either medicine alone.

Palbociclib (Ibrance) gained FDA approval on February 3, 2015. A palbociclib generic is available.

Palbociclib is approved to treat:

• Hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced or metastatic breast cancer in adults, in combination with: An aromatase inhibitor as initial endocrine-based therapy Fulvestrant in those with disease progression following endocrine therapy.
• Endocrine-resistant, PIK3CA-mutated, HR-positive, HER2-negative, locally advanced or metastatic breast cancer, as detected by an FDA-approved test, in combination with inavolisib and fulvestrant in adults following recurrence on or after completing adjuvant endocrine therapy
• HR-positive, HER2-positive locally advanced or metastatic breast cancer in adults, in combination with trastuzumab, with or without pertuzumab, and endocrine therapy, as maintenance treatment following induction treatment.

Palbociclib is supported across its FDA indications by four pivotal breast cancer trials.

• PALOMA-1 (NCT00721409), a phase 2 study, formed the basis for accelerated first-line approval with an aromatase inhibitor; and the confirmatory phase 3 PALOMA-2 (NCT01740427) showed a median progression-free survival (PFS) of 27.6 months with palbociclib plus letrozole versus 14.5 months.
• PALOMA-3 (NCT01942135) supported the fulvestrant combination after endocrine progression, with a median PFS of 11.2 months versus 4.6 months. INAVO120 (NCT04191499) backed the inavolisib-plus-fulvestrant regimen in PIK3CA-mutated, endocrine-resistant disease, with PFS of 15.0 versus placebo and an OS benefit.
• PATINA (NCT02947685) supported the 2026 HR-positive, HER2-positive maintenance indication, reducing the risk of cancer progression or death by 24%, compared with the same treatment without Palbociclib.

Take palbociclib exactly as your healthcare provider tells you. Palbociclib is available as tablets or capsules.

Palbociclib tablets

• Palbociclib tablets may be taken with or without food.
• Take about the same time each day.
• Swallow palbociclib tablets whole. Do not chew, crush, or split palbociclib tablets before swallowing them.
• Do not take any palbociclib tablets that are broken, cracked, or that look damaged.
• Avoid grapefruit and grapefruit products during treatment with palbociclib. Grapefruit may increase the amount of palbociclib in your blood.
• Do not change your dose or stop taking palbociclib unless your healthcare provider tells you.
• If you miss a dose of palbociclib or vomit after taking a dose of palbociclib, do not take another dose on that day. Take your next dose at your regular time.
• When palbociclib is used in combination with inavolisib and fulvestrant, trastuzumab, pertuzumab, or an aromatase inhibitor, also read the Patient Information for the prescribed products.

Palbociclib capsules

• Take palbociclib capsules with food.
• Take about the same time each day.
• Swallow palbociclib capsules whole. Do not chew, crush, or open palbociclib capsules before swallowing them.
• Do not take any palbociclib capsules that are broken, cracked, or that look damaged.
• Avoid grapefruit and grapefruit products during treatment with palbociclib. Grapefruit may increase the amount of palbociclib in your blood.
• Do not change your dose or stop taking palbociclib unless your healthcare provider tells you.
• If you miss a dose of palbociclib or vomit after taking a dose of palbociclib, do not take another dose on that day. Take your next dose at your regular time.
• When palbociclib is used in combination with inavolisib and fulvestrant, trastuzumab, pertuzumab, or an aromatase inhibitor, also read the Patient Information for the prescribed products.

Before taking palbociclib, tell your healthcare provider about all of your medical conditions, including if you:

• Have a fever, chills, or any other signs or symptoms of infection
• Have liver or kidney problems
• Have any other medical conditions
• Are pregnant, or plan to become pregnant
• Are breastfeeding or plan to breastfeed.

Pregnancy

Palbociclib can harm your unborn baby. Females who can become pregnant should use effective birth control during treatment and for at least 3 weeks after the last dose of palbociclib.

• Your healthcare provider may ask you to take a pregnancy test before you start treatment with palbociclib.

Males with female partners who can become pregnant should use effective birth control during treatment with Palbociclib for at least 3 months after the last dose of palbociclib.

Talk to your healthcare provider about birth control methods that may be right for you during this time.

If you become pregnant or think you are pregnant, tell your healthcare provider right away.

Breastfeeding

It is not known if palbociclib passes into your breast milk. Do not breastfeed during treatment with Palbociclib and for 3 weeks after the last dose.

Common side effects

The most common side effects of palbociclib when used with either letrozole or fulvestrant are:

• Low red blood cell counts and low platelet counts. Call your healthcare provider every day if you develop any of these symptoms during treatment: Dizziness Shortness of breath Weakness Bleeding or bruising more easily Nosebleeds.
• Infections
• Increased liver enzyme blood tests
• Tiredness
• Nausea
• Sore mouth
• Diarrhea
• Hair thinning or hair loss
• Increased blood creatinine.

The most common side effects when inavolisib is added to palbociclib plus fulvestrant are:

• High blood sugar levels causing excessive thirst and urination
• Sore mouth
• Diarrhea
• Decreased white blood cell counts, red blood cell counts, and platelet counts
• Decreased blood levels of calcium, potassium, sodium, and magnesium
• Increased creatinine blood levels
• Tiredness
• Abnormalities in liver blood tests
• Nausea
• Rash
• Loss of appetite
• COVID-19 infection
• Headaches.

The most common side effects of palbociclib when used with trastuzumab, with or without pertuzumab, and hormonal therapy are:

• Decreased white blood cell counts, red blood cell counts, and platelet counts
• Increased creatinine blood levels
• Diarrhea
• Infections
• Sore mouth
• Increased liver enzymes
• Decreased blood levels of calcium and potassium
• Tiredness
• Nausea
• Weakness
• Headaches
• Rash
• Itching
• Muscle spasms.

Palbociclib may cause fertility problems in males. This may affect your ability to father a child. Talk to your healthcare provider about family planning options before starting palbociclib if this is a concern for you.

Serious Side Effects and Warnings

Palbociclib may cause the following serious side effects:

• Low white blood cell counts (neutropenia) are very common when taking palbociclib and may cause serious infections that can lead to death. Your healthcare provider should check your white blood cell counts before and during treatment.

If you develop low white blood cell counts during treatment with palbociclib, your healthcare provider may stop your treatment, decrease your dose, or tell you to wait to begin your treatment cycle. Tell your healthcare provider right away if you have signs and symptoms of low white blood cell counts or infections such as fever and chills.

• Lung problems (pneumonitis). Palbociclib may cause severe or life-threatening inflammation of the lungs during treatment that can lead to death. Tell your healthcare provider right away if you have any new or worsening symptoms, including: chest pain cough with or without mucus trouble breathing or shortness of breath.

Your healthcare provider may interrupt or stop treatment with palbociclib completely if your symptoms are severe.

It is not known if palbociclib is safe and effective in children.

Tell your healthcare provider if you have any side effect that bothers you or do not go away. These are not all of the possible side effects of palbociclib. Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Dose of palbociclib tablets for HR+ breast cancer

• Initial: 125 mg orally 1 time daily with or without food for 21 days, followed by 7 days without treatment.

Dose of palbociclib capsules for HR+ breast cancer

• Initial: 125 mg orally 1 time daily with food for 21 days, followed by 7 days without treatment.

If you miss a dose of palbociclib or vomit after taking a dose of palbociclib, do not take another dose on that day. Take your next dose at your regular time.

If you take too much palbociclib, call your healthcare provider right away or go to the nearest hospital emergency room.

Tell your healthcare provider about all of the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements. Palbociclib and other medicines may affect each other, causing side effects. Especially tell your healthcare provider if you take:

• CYP3A Inhibitors, such as clarithromycin, indinavir, itraconazole, ketoconazole, lopinavir/ritonavir, nefazodone, nelfinavir, posaconazole, ritonavir, saquinavir, telaprevir, telithromycin, and voriconazole. These should not be taken at the same time as palbociclib. If a strong CYP3A inhibitor cannot be avoided, your healthcare provider should reduce the dose of palbociclib
• CYP3A Inducers, such as glucocorticoids, rifampin, carbamazepine, phenobarbital, and phenytoin. Avoid using these at the same time as palbociclib
• CYP3A substrates, such as cyclosporin, tricyclic antidepressants, and some chemotherapy agents. The dose of sensitive CYP3A4 substrates with narrow therapeutic indices may need to be reduced when given concurrently with palbociclib.

Avoid grapefruit and grapefruit products.

Know the medicines you take. Keep a list of them to show your healthcare provider or pharmacist when you get a new medicine. This is not a full list of interactions with palbociclib. See the palbociclib prescribing information for a complete list.

Store palbociclib at 68 °F to 77 °F (20 °C to 25 °C) in the original blister pack.

Keep out of reach of children.

Active ingredient: palbociclib

Inactive ingredients (tablets ):

Microcrystalline cellulose, colloidal silicon dioxide, crospovidone, magnesium stearate, succinic acid, HPMC 2910/hypromellose, titanium dioxide, triacetin, and FD&C Blue #2/Indigo Carmine Aluminum Lake.

In addition, the 75 mg and 125 mg tablets contain red iron oxide, and the 100 mg tablets contain yellow iron oxide.

Inactive ingredients (capsules):

Microcrystalline cellulose, lactose monohydrate, sodium starch glycolate, colloidal silicon dioxide, magnesium stearate, and hard gelatin capsule shells.

The light orange, light orange/caramel, and caramel opaque capsule shells contain gelatin, red iron oxide, yellow iron oxide, and titanium dioxide.

The printing ink contains: shellac, titanium dioxide, ammonium hydroxide, propylene glycol, and simethicone.

Palbociclib is manufactured under the brand name Ibrance by Pfizer Labs, a division of Pfizer Inc., New York, NY 10001.

Synthon Pharms Inc. makes a generic palbociclib tablet, but a generic palbociclib capsule is not available.