Palbociclib

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{{DrugProjectFormSinglePage |authorTag=Alberto Plate [1] |genericName=Palbociclib |aOrAn=a |drugClass=cyclin-dependent kinase inhibitor |indicationType=treatment |indication=postmenopausal women with estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer as initial endocrine-based therapy for their metastatic disease, in combination with letrozole. This indication is approved under accelerated approval based on progression-free survival (PFS). Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial |adverseReactions=neutropenia, leukopenia, fatigue, anemia, upper respiratory infection, nausea, stomatitis, alopecia, diarrhea, thrombocytopenia, decreased appetite, vomiting, asthenia, peripheral neuropathy, and epistaxis |blackBoxWarningTitle=TITLE |blackBoxWarningBody=Condition Name: (Content) |offLabelAdultGuideSupport=There is limited information regarding Off-Label Guideline-Supported Use of Palbociclib in adult patients. |offLabelAdultNoGuideSupport=There is limited information regarding Off-Label Non–Guideline-Supported Use of Palbociclib in adult patients. |offLabelPedGuideSupport=There is limited information regarding Off-Label Guideline-Supported Use of Palbociclib in pediatric patients. |offLabelPedNoGuideSupport=There is limited information regarding Off-Label Non–Guideline-Supported Use of Palbociclib in pediatric patients. |contraindications=*None |warnings=====Neutropenia====

  • Decreased neutrophil counts have been observed in clinical trials with IBRANCE. Grade 3 (57%) or 4 (5%) decreased neutrophil counts were reported in patients receiving IBRANCE plus letrozole in the randomized clinical trial (Study 1). Median time to first episode of any grade neutropenia per laboratory data was 15 days (13–117 days). Median duration of Grade ≥3 neutropenia was 7 days.
  • Febrile neutropenia events have been reported in the IBRANCE clinical program, although no cases of febrile neutropenia have been observed in Study 1. Monitor complete blood count prior to starting IBRANCE therapy and at the beginning of each cycle, as well as on Day 14 of the first two cycles, and as clinically indicated. Dose interruption, dose reduction or delay in starting treatment cycles is recommended for patients who develop Grade 3 or 4 neutropenia.

Infections

  • Infections have been reported at a higher rate in patients treated with IBRANCE plus letrozole compared to patients treated with letrozole alone in Study 1. Grade 3 or 4 infections occurred in 5% of patients treated with IBRANCE plus letrozole whereas no patients treated with letrozole alone experienced a Grade 3 or 4 infection. Monitor patients for signs and symptoms of infection and treat as medically appropriate.

Pulmonary Embolism

  • Pulmonary embolism has been reported at a higher rate in patients treated with IBRANCE plus letrozole (5%) compared with no cases in patients treated with letrozole alone in Study 1. Monitor patients for signs and symptoms of pulmonary embolism and treat as medically appropriate.

Embryo-Fetal Toxicity

  • Based on findings in animals and mechanism of action, IBRANCE can cause fetal harm. IBRANCE caused embryo-fetal toxicities in rats and rabbits at maternal exposures that were greater than or equal to 4 times the human clinical exposure based on area under the curve (AUC). Advise females of reproductive potential to use effective contraception during therapy with IBRANCE and for at least two weeks after the last dose.

|clinicalTrials=The following topics are described below and elsewhere in the labeling:

Clinical Studies Experience

  • Because clinical trials are conducted under varying conditions, the adverse reaction rates observed cannot be directly compared to rates in other trials and may not reflect the rates observed in clinical practice.
  • The safety of IBRANCE (125 mg/day) plus letrozole (2.5 mg/day) versus letrozole alone was evaluated in Study 1. The data described below reflect exposure to IBRANCE in 83 out of 160 patients with ER-positive, HER2-negative advanced breast cancer who received at least 1 dose of treatment in Study 1. The median duration of treatment for palbociclib was 13.8 months while the median duration of treatment for letrozole on the letrozole-alone arm was 7.6 months.
  • Dose reductions due to an adverse reaction of any grade occurred in 36% of patients receiving IBRANCE plus letrozole. No dose reduction was allowed for letrozole in Study 1.
  • Permanent discontinuation due to an adverse reaction occurred in 7 of 83 (8%) patients receiving IBRANCE plus letrozole and in 2 of 77 (3%) patients receiving letrozole alone. Adverse reactions leading to discontinuation for those patients receiving IBRANCE plus letrozole included neutropenia (6%), asthenia (1%), and fatigue (1%).
  • The most common adverse reactions (≥10%) of any grade reported in patients in the IBRANCE plus letrozole arm were neutropenia, leukopenia, fatigue, anemia, upper respiratory infection, nausea, stomatitis, alopecia, diarrhea, thrombocytopenia, decreased appetite, vomiting, asthenia, peripheral neuropathy, and epistaxis.
  • The most frequently reported serious adverse reactions in patients receiving IBRANCE plus letrozole were pulmonary embolism (3 of 83; 4%) and diarrhea (2 of 83; 2%).

An increase incidence of infections events was observed in the palbociclib plus letrozole arm (55%) compared to the letrozole alone arm (34%). Febrile neutropenia events have been reported in the IBRANCE clinical program, although no cases were observed in Study 1. Grade ≥3 neutropenia was managed by dose reductions and/or dose delay or temporary discontinuation consistent with a permanent discontinuation rate of 6% due to neutropenia.

Adverse drug reactions (≥10%) reported in patients who received IBRANCE plus letrozole or letrozole alone in Study 1 are listed in Table 4.

|drugInteractions=Palbociclib is primarily metabolized by CYP3A and sulfotransferase (SULT) enzyme SULT2A1. In vivo, palbociclib is a time-dependent inhibitor of CYP3A.

Agents That May Increase Palbociclib Plasma Concentrations

Effect of CYP3A Inhibitors

Agents That May Decrease Palbociclib Plasma Concentrations

Effect of CYP3A Inducers

Drugs That May Have Their Plasma Concentrations Altered by Palbociclib

|useInPregnancyFDA=====Risk Summary====

  • Based on findings in animals and mechanism of action, IBRANCE can cause fetal harm when administered to a pregnant woman. In animal studies, palbociclib was teratogenic and fetotoxic at maternal exposures that were ≥4 times the human clinical exposure based on AUC at the recommended human dose. There are no available human data informing the drug-associated risk. Advise pregnant women of the potential risk to a fetus. The background risk of major birth defects and miscarriage for the indicated population is unknown. However, the background risk in the U.S. general population of major birth defects is 2–4% and of miscarriage is 15–20% of clinically recognized pregnancies.
Data
  • Animal Data: In a fertility and early embryonic development study in female rats, palbociclib was administered orally for 15 days before mating through to Day 7 of pregnancy, which did not cause embryo toxicity at doses up to 300 mg/kg/day with maternal systemic exposures approximately 4 times the human exposure (AUC) at the recommended dose. In embryo-fetal development studies in rats and rabbits, pregnant animals received oral doses up to 300 mg/kg/day and 20 mg/kg/day palbociclib, respectively, during the period of organogenesis. The maternally toxic dose of 300 mg/kg/day was fetotoxic in rats, resulting in reduced fetal body weights. At doses ≥100 mg/kg/day in rats, there was an increased incidence of a skeletal variation (increased incidence of a rib present at the seventh cervical vertebra). At the maternally toxic dose of 20 mg/kg/day in rabbits, there was an increased incidence of skeletal variations, including small phalanges in the forelimb. At 300 mg/kg/day in rats and 20 mg/kg/day in rabbits, the maternal systemic exposures were approximately 4 and 9 times the human exposure (AUC) at the recommended dose. CDK4/6 double knockout mice have been reported to die in late stages of fetal development (gestation Day 14.5 until birth) due to severe anemia. However, knockout mouse data may not be predictive of effects in humans due to differences in degree of target inhibition.

|useInNursing=*There are no data on the presence of palbociclib in human milk, the effects of IBRANCE on the breastfed child, or the effects of IBRANCE on milk production. Because many drugs are excreted in human milk and because of the potential for serious adverse reactions in nursing infants from IBRANCE, advise a nursing woman to discontinue breastfeeding during treatment with IBRANCE. |useInPed=*The safety and efficacy of IBRANCE in pediatric patients have not been studied. |useInGeri=*Of 84 patients who received IBRANCE in Study 1, 37 patients (44%) were ≥65 years of age and 8 patients (10%) were ≥75 years of age. No overall differences in safety or effectiveness of IBRANCE were observed between these patients and younger patients but greater sensitivity of some older individuals cannot be ruled out. |useInRenalImpair=*Based on a population pharmacokinetic analysis that included 183 patients, where 73 patients had mild renal impairment (60 mL/min ≤ CrCl <90 mL/min) and 29 patients had moderate renal impairment (30 mL/min ≤ CrCl <60 mL/min), mild and moderate renal impairment had no effect on the exposure of palbociclib. The pharmacokinetics of palbociclib have not been studied in patients with severe renal impairment |useInHepaticImpair=*Based on a population pharmacokinetic analysis that included 183 patients, where 40 patients had mild hepatic impairment (total bilirubin ≤ ULN and AST > ULN, or total bilirubin >1.0 to 1.5 × ULN and any AST), mild hepatic impairment had no effect on the exposure of palbociclib. The pharmacokinetics of palbociclib have not been studied in patients with moderate or severe hepatic impairment (total bilirubin >1.5 × ULN and any AST) |useInReproPotential=====Contraception====

  • Females: Advise females of reproductive potential to use effective contraception during treatment with IBRANCE and for at least two weeks after the last dose. Advise females to contact their healthcare provider if they become pregnant, or if pregnancy is suspected, during treatment with IBRANCE.

Infertility

  • Males: Based on findings in animals, male fertility may be compromised by treatment with IBRANCE [see CARCINOGENESIS, MUTAGENESIS, IMPAIRMENT OF FERTILITY (13.1)].

|drugBox={{Drugbox2 | drug_name = Palbociclib | IUPAC_name = 6-Acetyl-8-cyclopentyl-5-methyl-2-{[5-(1-piperazinyl)-2-pyridinyl]amino}pyrido[2,3-d]pyrimidin-7(8H)-one | image = Palbociclib Structure.png | alt = | caption =

| tradename = Ibrance | Drugs.com = | MedlinePlus = | pregnancy_AU = | pregnancy_US = | pregnancy_category= | legal_AU = | legal_CA = | legal_UK = | legal_US = | legal_status = Investigational | routes_of_administration =

| bioavailability = | protein_bound = | metabolism = | elimination_half-life = | excretion =

| CAS_number = | ATCvet = | ATC_prefix = None | ATC_suffix = | PubChem = 5330286 | ChemSpiderID = 4487437 | DrugBank = | synomys = PD-0332991

| C=24 | H=29 | N=7 | O=2 | molecular_weight = 447.533 g/mol | smiles = O=C2N(c1nc(ncc1/C(=C2/C(=O)C)C)Nc3ncc(cc3)N4CCNCC4)C5CCCC5 | InChI = 1/C24H29N7O2/c1-15-19-14-27-24(28-20-8-7-18(13-26-20)30-11-9-25-10-12-30)29-22(19)31(17-5-3-4-6-17)23(33)21(15)16(2)32/h7-8,13-14,17,25H,3-6,9-12H2,1-2H3,(H,26,27,28,29) | InChIKey = AHJRHEGDXFFMBM-UHFFFAOYAM | StdInChI = 1S/C24H29N7O2/c1-15-19-14-27-24(28-20-8-7-18(13-26-20)30-11-9-25-10-12-30)29-22(19)31(17-5-3-4-6-17)23(33)21(15)16(2)32/h7-8,13-14,17,25H,3-6,9-12H2,1-2H3,(H,26,27,28,29) | StdInChIKey = AHJRHEGDXFFMBM-UHFFFAOYSA-N }} |mechAction=*Palbociclib is an inhibitor of cyclin-dependent kinase (CDK) 4 and 6. Cyclin D1 and CDK4/6 are downstream of signaling pathways which lead to cellular proliferation. In vitro, palbociclib reduced cellular proliferation of estrogen receptor (ER)-positive breast cancer cell lines by blocking progression of the cell from G1 phase into S phase of the cell cycle. Treatment of breast cancer cell lines with the combination of palbociclib and antiestrogens leads to decreased retinoblastoma protein (Rb) phosphorylation resulting in reduced E2F expression and signaling and increased growth arrest compared to treatment with each drug alone. In vitro treatment of ER-positive breast cancer cell lines with the combination of palbociclib and antiestrogens leads to increased cell senescence, which was sustained for up to 6 days following drug removal. In vivo studies using a patient-derived ER-positive breast cancer xenograft model demonstrated that the combination of palbociclib and letrozole increased the inhibition of Rb phosphorylation, downstream signaling and tumor growth compared to each drug alone. |structure=*The molecular weight is 447.54 daltons. The chemical name is 6-acetyl-8-cyclopentyl-5-methyl-2-{[5-(piperazin-1-yl)pyridin-2-yl]amino}pyrido[2,3-d]pyrimidin-7(8H)-one, and its structural formula is:

|PD=====Cardiac Electrophysiology====

  • The effect of palbociclib on the QTc interval was evaluated in 184 patients with advanced cancer. No large change (i.e., >20 ms) in the QTc interval was detected at the mean observed maximal steady-state palbociclib concentration following a therapeutic schedule (e.g., 125 mg daily for 21 consecutive days followed by 7 days off to comprise a complete cycle of 28 days).

|PK=The pharmacokinetics of palbociclib were characterized in patients with solid tumors including advanced breast cancer and in healthy subjects.

Absorption

  • The mean Cmax of palbociclib is generally observed between 6 to 12 hours (time to reach maximum concentration, Tmax) following oral administration. The mean absolute bioavailability of IBRANCE after an oral 125 mg dose is 46%. In the dosing range of 25 mg to 225 mg, the AUC and Cmax increased proportionally with dose in general. Steady state was achieved within 8 days following repeated once daily dosing. With repeated once daily administration, palbociclib accumulated with a median accumulation ratio of 2.4 (range 1.5–4.2).
  • Food effect: Palbociclib absorption and exposure were very low in approximately 13% of the population under the fasted condition. Food intake increased the palbociclib exposure in this small subset of the population, but did not alter palbociclib exposure in the rest of the population to a clinically relevant extent. Therefore, food intake reduced the intersubject variability of palbociclib exposure, which supports administration of IBRANCE with food. Compared to IBRANCE given under overnight fasted conditions, the population average AUCinf and Cmax of palbociclib increased by 21% and 38%, respectively, when given with high-fat, high-calorie food (approximately 800 to 1000 calories with 150, 250, and 500 to 600 calories from protein, carbohydrate and fat, respectively), by 12% and 27%, respectively, when given with low-fat, low-calorie food (approximately 400 to 500 calories with 120, 250, and 28 to 35 calories from protein, carbohydrate and fat, respectively), and by 13% and 24%, respectively, when moderate-fat, standard calorie food (approximately 500 to 700 calories with 75 to 105, 250 to 350 and 175 to 245 calories from protein, carbohydrate and fat, respectively) was given one hour before and two hours after IBRANCE dosing.

Distribution

  • Binding of palbociclib to human plasma proteins in vitro was approximately 85%, with no concentration dependence over the concentration range of 500 ng/mL to 5000 ng/mL. The geometric mean apparent volume of distribution (Vz/F) was 2583 L (26% CV).

Metabolism

  • In vitro and in vivo studies indicated that palbociclib undergoes hepatic metabolism in humans. Following oral administration of a single 125 mg dose of [14C]palbociclib to humans, the primary metabolic pathways for palbociclib involved oxidation and sulfonation, with acylation and glucuronidation contributing as minor pathways. Palbociclib was the major circulating drug-derived entity in plasma (23%). The major circulating metabolite was a glucuronide conjugate of palbociclib, although it only represented 1.5% of the administered dose in the excreta. Palbociclib was extensively metabolized with unchanged drug accounting for 2.3% and 6.9% of radioactivity in feces and urine, respectively. In feces, the sulfamic acid conjugate of palbociclib was the major drug-related component, accounting for 26% of the administered dose. In vitro studies with human hepatocytes, liver cytosolic and S9 fractions, and recombinant SULT enzymes indicated that CYP3A and SULT2A1 are mainly involved in the metabolism of palbociclib.

Elimination

  • The geometric mean apparent oral clearance (CL/F) of palbociclib was 63.1 L/hr (29% CV), and the mean (± standard deviation) plasma elimination half-life was 29 (±5) hours in patients with advanced breast cancer. In 6 healthy male subjects given a single oral dose of [14C]palbociclib, a median of 91.6% of the total administered radioactive dose was recovered in 15 days; feces (74.1% of dose) was the major route of excretion, with 17.5% of the dose recovered in urine. The majority of the material was excreted as metabolites.

|nonClinToxic=====Carcinogenesis, Mutagenesis, Impairment of Fertility====

  • Carcinogenicity studies have not been conducted with palbociclib.
  • Palbociclib was clastogenic in an in vitro micronucleus assay in Chinese Hamster Ovary cells and in vivo in the bone marrow of male rats that received doses ≥100 mg/kg/day for three weeks. Clastogenicity occurred via an aneugenic mechanism. Palbociclib was not mutagenic in an in vitro bacterial reverse mutation (Ames) assay and did not induce structural chromosomal aberrations in the in vitro human lymphocyte chromosome aberration assay.
  • In a fertility study in female rats, palbociclib did not affect mating or fertility at any dose up to 300 mg/kg/day (approximately 4 times human clinical exposure based on AUC) and no adverse effects were observed in the female reproductive tissues in repeat-dose toxicity studies up to 300 mg/kg/day in the rat and 3 mg/kg/day in the dog (approximately 6 times and similar to human exposure (AUC), at the recommended dose, respectively). Male fertility studies with palbociclib have not been conducted; however, in repeat-dose toxicity studies, testicular degeneration was observed in rats and dogs at 30 and 0.2 mg/kg/day, respectively (approximately 11 and 0.1 times human exposure (AUC), at the recommended dose, respectively), which was partially reversible in the rat and dog following a 12-week non-dosing period.

Animal Toxicology and/or Pharmacology

|clinicalStudies=*Study 1 was a randomized, open-label, multicenter study of IBRANCE plus letrozole versus letrozole alone conducted in postmenopausal women with ER-positive, HER2-negative advanced breast cancer who had not received previous systemic treatment for their advanced disease. A total of 165 patients were randomized in Study 1. Randomization was stratified by disease site (visceral versus bone only versus other) and by disease-free interval (>12 months from the end of adjuvant treatment to disease recurrence versus ≤12 months from the end of adjuvant treatment to disease recurrence or de novo advanced disease). IBRANCE was given orally at a dose of 125 mg daily for 21 consecutive days followed by 7 days off treatment. Patients received study treatment until progressive disease, unmanageable toxicity, or consent withdrawal.

  • Patients enrolled in this study had a median age of 63 years (range 38 to 89). The majority of patients were Caucasian (90%) and all patients had an Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0 or 1. Forty-three percent of patients had received chemotherapy and 33% had received antihormonal therapy in the neoadjuvant or adjuvant setting prior to their diagnosis of advanced breast cancer. Forty-nine percent of patients had no prior systemic therapy in the neoadjuvant or adjuvant setting. The majority of patients (98%) had metastatic disease. Nineteen percent of patients had bone only disease and 48% of patients had visceral disease.
  • The major efficacy outcome measure of the study was investigator-assessed PFS evaluated according to Response Evaluation Criteria in Solid Tumors Version 1.0 (RECIST). Major efficacy results from Study 1 are summarized in Table 6 and Figure 1. Consistent results were observed across patient subgroups of, disease-free interval, disease site and prior therapy. The treatment effect of the combination on PFS was also supported by a retrospective independent review of radiographs with an observed hazard ratio (HR) of 0.621 (95% CI: 0.378, 1.019). Overall response rate in patients with measurable disease as assessed by the investigator was higher in the IBRANCE plus letrozole compared to the letrozole alone arm (55.4% versus 39.4%). At the time of the final analysis of PFS, overall survival (OS) data was not mature with 37% of events.

|alcohol=Alcohol-Palbociclib interaction has not been established. Talk to your doctor about the effects of taking alcohol with this medication. }}

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