Recent Updates
Recently added Catalysts

PD-0332991

Phase 3

Breast Neoplasms | Small molecule | Oncology |Pfizer, Inc.|Last Updated: May 14, 2026

Target and mechanism

Molecular targetCDK4, CCND1, CDK6
Target classInhibitor
ModalitySmall molecule

Also known as Palbociclib, palbociclib

Success Probability

Subscribe to view

Market & Valuation

Subscribe to view

Trial Design

RandomizedDouble-BlindACTIVE_CONTROLLEDDMC
Total Trials2
Total Enrollment1,006

FDA Designations

No designations recorded

Clinical trial landscape

PD-0332991 · 5 trials · 4 indications

Phase 3 2Phase 2 1Phase 1 2
NCT02297438A Study Of Palbociclib (PD-0332991) + Letrozole VS. Placebo+ Letrozole For 1st Line Treatment Of Asian Postmenopausal Women With ER+/HER2- Advanced Breast Cancer [PALOMA-4]Breast Neoplasms
COMPLETED340 Analytics
NCT01740427A Study of Palbociclib (PD-0332991) + Letrozole vs. Letrozole For 1st Line Treatment Of Postmenopausal Women With ER+/HER2- Advanced Breast Cancer (PALOMA-2)Breast Neoplasms
COMPLETED666 Analytics
PHASE3COMPLETED
A Study Of Palbociclib (PD-0332991) + Letrozole VS. Placebo+ Letrozole For 1st Line Treatment Of Asian Postmenopausal Women With ER+/HER2- Advanced Breast Cancer [PALOMA-4]
Breast NeoplasmsUnlock trial analytics
PHASE3COMPLETED
A Study of Palbociclib (PD-0332991) + Letrozole vs. Letrozole For 1st Line Treatment Of Postmenopausal Women With ER+/HER2- Advanced Breast Cancer (PALOMA-2)
Breast NeoplasmsUnlock trial analytics

Study Endpoints

Primary Endpoints

Progression-Free Survival (PFS) Based on Investigator's Assessment: Up to Primary Completion Date
Randomization up to 65 months

PFS was based on Kaplan-Meier estimates. PFS was defined as the time from the date of randomization to the date of the first documentation of objective progression of disease (PD) or death due to any cause in the absence of documented PD, whichever occurred first. PD is defined using Response Evaluation Criteria In Solid Tumors Criteria (RECIST v1.1) as a 20% increase in the sum of diameters of target measurable lesions above the smallest sum observed (over baseline if no decrease in the sum is observed during therapy), with a minimum absolute increase of 5 mm. In this outcome measure, PFS was based on investigator's assessment.

Progression-Free Survival (PFS) as Assessed by the Investigator
From randomization date to date of first documentation of progression or death (up to approximately 2.5 years)

PFS is defined as the time from the date of randomization to the date of the first documentation of objective tumor progression as per Response Evaluation Criteria In Solid Tumors Criteria (RECIST v1.1) or death due to any cause in the absence of documented PD, whichever occurs first. If tumor progression data include more than 1 date, the first date will be used. PFS (in months) will be calculated as (first event date - randomization date +1)/30.4. Progression is defined using RECIST v1.1, as a 20% increase in the sum of diameters of target measurable lesions above the smallest sum observed (over baseline if no decrease in the sum is observed during therapy), with a minimum absolute increase of 5 mm, or unequivocal progression of pre-existing non-target lesions, or the appearance of new lesions.

Number of Participants With Dose Limiting Toxicities (DLT): Part 1 Phase 1
Lead-in period (Day -7) up to Day 28 (Cycle 1)

DLT was classified as per common terminology criteria for adverse events (CTCAE) version 4.0 as any of the events occurring during 28 days of Cycle 1,attributed to study drug:grade 4 neutropenia(for a duration of greater than \[\>\]7 days); febrile neutropenia (grade greater than or equal to \[\>=\]3 neutropenia,body temperature \>=38.5 degree Celsius);grade \>=3 thrombocytopenia with bleeding episode;grade 4 thrombocytopenia;grade \>=3 non-hematologic toxicity except grade 3 or more nausea, vomiting,electrolyte abnormality(if controllable by therapy);grade 3 QTc prolongation(\>500 millisecond \[msec\])persist after correction of reversible cause such as electrolyte abnormalities or hypoxia. Lack of hematologic recovery (platelets less than \[\<\]50,000/microliter \[mcL\],absolute neutrophil count \<1,000/mcL,hemoglobin \<8.0 gram/deciliter \[g/dL\]) or prolonged non hematologic toxicities that delays initiation of next dose by \>7 days;receipt of \<75 percent of planned dose in first cycle due to toxicity.

Number of Participants With Treatment-Related Adverse Events (AEs) and Serious Adverse Events (SAEs): Part 2 Phase 1
Baseline (Day 1) up to 28 days after last dose of study drug (up to 1673 days)

A treatment related AE is any untoward medical occurrence in a clinical investigation participant administered a product or medical device; the event had a causal relationship with the treatment or usage. A SAE was an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly. Relatedness was judged by investigator. AEs included both serious and non-serious adverse events.

Number of Participants With Treatment-Emergent Adverse Events (TEAEs) By Severity: Part 2 Phase 1
Baseline (Day 1) up to 28 days after last dose of study drug (up to 1673 days)

AE was any untoward medical occurrence in a participant who received study drug without regard to possibility of causal relationship. An AE was considered treatment emergent if occurred for the first time after the start of study treatment or occurred prior to the start of treatment but increased in National Cancer Institute (NCI) CTCAE grade during study treatment period. AE severity was defined to be the maximum toxicity grade of the TEAEs experienced by the participants during the study. AE was assessed according to severity as: Grade 1 (mild AE), Grade 2 (moderate AE), Grade 3 (severe AE), Grade 4 (life-threatening consequences) and Grade 5 (death related to AE).

Percentage of Participants With 1 Year Progression Free Survival (PFS): Phase 2
From initiation of treatment up to 12 months

PFS was defined as the time from first dose of study treatment to the date of the first documentation of objective progression of disease (PD) or death due to any cause in the absence of documented PD, whichever occurred first. PD was defined using Response Evaluation Criteria In Solid Tumors Criteria (RECIST v1.1), as a 20% increase in the sum of the longest diameter of target lesions, or a measurable increase in a non-target lesion, or the appearance of new lesions.1-year PFS was defined as the percentage of participants without PFS events (PD or death due to any cause) at 12 months based on the Kaplan-Meier estimate. Percentage of participants with 1-year PFS with 90% confidence interval (CI) were reported.

Correlation Coefficient Between Change From Baseline in Fluoro-L-thymidine Positron Emission Tomography (FLT-PET) Maximum Standard Uptake Value (SUVmax) and in Phosphorylated Retinoblastoma (Phospho-Rb) Percent Positive Cells at Cycle 1 Day 21
Baseline, Cycle 1 Day 21

Maximum standard uptake value (SUVmax) was defined as the maximum value attained for the ratio of tissue radioactivity concentration at any time and the injected radioactivity concentration divided by the body weight (in kilogram \[kg\]). Phosphorylation of retinoblastoma (Rb) protein in the tumor cells, expressed as phospho-Rb percent positive cells, was assessed using Immunohistochemical staining technique. Change from baseline in \[(18)F\]-FLT-PET SUVmax at Cycle 1 Day 21 and change from baseline in Phospho-Rb percent positive cells at Cycle 1 Day 21 were analyzed. The change values of FLT-PET SUVmax and Phospho-Rb percent positive cells were then correlated. Here, 'N' (number of participants analyzed) signifies participants evaluable for this measure.

Correlation Coefficient Between Change From Baseline in Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) Maximum Standard Uptake Value (SUVmax) and in Phosphorylated Retinoblastoma (Phospho-Rb) Percent Positive Cells at Cycle 1 Day 21
Baseline, Cycle 1 Day 21

Maximum standard uptake value (SUVmax) was defined as the maximum value attained for the ratio of tissue radioactivity concentration at any time and the injected radioactivity concentration divided by the body weight (in kilogram \[kg\]). Phosphorylation of retinoblastoma (Rb) protein in the tumor cells, expressed as phospho-Rb percent positive cells, was assessed using Immunohistochemical staining technique. Change from baseline in \[(18)F\]-FDG-PET SUVmax at Cycle 1 Day 21 and change from baseline in Phospho-Rb percent positive cells at Cycle 1 Day 21 were analyzed. The change values of FLT-PET SUVmax and Phospho-Rb percent positive cells were then correlated. Here, 'N' (number of participants analyzed) signifies participants evaluable for this measure.

Change From Baseline in Maximum Standard Uptake Value (SUVmax) at Cycle 1 Day 21
Baseline, Cycle 1 Day 21

Maximum standard uptake value (SUVmax) was defined as the maximum value attained for the ratio of tissue radioactivity concentration at any time and the injected radioactivity concentration divided by the body weight (in kilogram \[kg\]). Change from baseline in SUVmax was assessed using \[(18)F\]-FLT-PET and \[(18)F\]-FDG-PET techniques.

Correlation Between Positron Emission Tomography (PET) Response and Progression-Free Survival (PFS)
Baseline, Cycle 1 Day 21 for PET response; Screening until tumor progression or death, assessed on Day 1 of every alternate cycle starting from Cycle 1 up to end of treatment (Day 609) or early withdrawal (if not completed during last 6 weeks) for PFS

PET response was defined as complete response (CR) = mean SUVmax same as of background; partial response (PR) = mean SUVmax less than (\<) 75 percent (%) of baseline; progressive disease (PD) = mean SUVmax greater than (\>) 125% of baseline; stable disease (SD) = mean SUVmax greater than or equal to (\>=) 75% of baseline and mean SUVmax less than or equal to (\<=) 125% of baseline. PFS was defined as the time from first dose of study medication to the first documentation of objective tumor progression, or to death due to any cause, whichever occurred first. Tumor progression was defined as \>50% increase in sum of products of diameters, of dominant nodes and documented non-nodal sites or appearance of new sites of disease.

Correlation Between Positron Emission Tomography (PET) Response and Objective Response (OR)
Baseline, Cycle 1 Day 21 for PET response; Screening until tumor progression or death, assessed on Day 1 of every alternate cycle starting from Cycle 1 up to end of treatment (Day 609) or early withdrawal (if not completed during last 6 weeks) for OR

OR: CR= disappearance of all clinical/radiographic evidence of disease, disease related symptoms and biochemical abnormalities, nodal masses regressed to normal size, if spleen and bone marrow were involved, spleen regressed to normal size and not palpable and clear infiltrate on repeat bone marrow aspiration; PR= dominant nodes decreased by \>50% in sum of products of diameters (SPD), no increase in size of other nodes/liver/spleen, lesions regressed by \>50% in SPD, no new sites of disease; SD= response \<PR and no PD, documented \>=1 time after start of therapy, no new sites of disease; PD= \>50% increase in SPD of dominant nodes and other nodes or appearance of new sites of disease. PET response: CR= mean SUVmax same as background; PR= mean SUVmax \<75% of baseline; PD= mean SUVmax \>125% of baseline; SD= mean SUVmax \>=75% of baseline but \<=125% of baseline. Correlation was reported as conjoint number of participants with PET response at Cycle 1 Day 21 and OR at end of study.

Phosphorylated Retinoblastoma (Phospho-Rb) Percent Positive Cells at Baseline
Baseline

Phosphorylation of retinoblastoma (Rb) protein in the tumor cells, expressed as phospho-Rb percent positive cells, was assessed using Immunohistochemical staining technique.

Phosphorylated Retinoblastoma (Phospho-Rb) Percent Positive Cells at Cycle 1 Day 21
Cycle 1 Day 21

Phosphorylation of retinoblastoma (Rb) protein in the tumor cells, expressed as phospho-Rb percent positive cells, was assessed using Immunohistochemical staining technique.

Ki-67 Composite Score at Baseline
Baseline

Percentage of Ki-67 positive cells was determined by Immunohistochemical staining technique. Composite score = (sum of each intensity category multiplied by percent of cells in that category). Intensity categories of staining (0 = no staining; 1 = weak staining; 2 = moderate staining; 3 = strong staining). Composite score ranges from 0 (no staining) to 300 (100% of cells with 3 staining intensity).

Ki-67 Composite Score at Cycle 1 Day 21
Cycle 1 Day 21

Percentage of Ki-67 positive cells was determined by Immunohistochemical staining technique. Composite score = (sum of each intensity category multiplied by percent of cells in that category). Intensity categories of staining (0 = no staining; 1 = weak staining; 2 = moderate staining; 3 = strong staining). Composite score ranges from 0 (no staining) to 300 (100% of cells with 3 staining intensity).

Cyclin D1 Composite Score at Baseline
Baseline

Percentage of Cyclin D1 positive cells was determined by Immunohistochemical staining technique. Composite score = (sum of each intensity category multiplied by percent of cells in that category). Intensity categories of staining (0 = no staining; 1 = weak staining; 2 = moderate staining; 3 = strong staining). Composite score ranges from 0 (no staining) to 300 (100% of cells with 3 staining intensity).

Cyclin D1 Composite Score at Cycle 1 Day 21
Cycle 1 Day 21

Percentage of Cyclin D1 positive cells was determined by Immunohistochemical staining technique. Composite score = (sum of each intensity category multiplied by percent of cells in that category). Intensity categories of staining (0 = no staining; 1 = weak staining; 2 = moderate staining; 3 = strong staining). Composite score ranges from 0 (no staining) to 300 (100% of cells with 3 staining intensity).

Number of Participants With Laboratory Test Abnormalities
Baseline up to 28 days after last dose of study medication

Criteria for laboratory test abnormality: Hematology (Hemoglobin \[\<0.8\*lower limit of normal {LLN}\], Platelets \[\<0.5\*LLN/ \>1.75\*upper limit of normal {ULN}\], White blood cells \[\<0.6\*LLN/ \>1.5\*ULN\], Lymphocytes, Neutrophils \[\<0.8\*LLN/ \>1.2\*ULN\], Basophils, Eosinophils, Monocytes \[\>1.2\*ULN\]); Liver Function (Total bilirubin \[\>1.5\*ULN\], Aspartate aminotransferase, Alanine aminotransferase, Lactate dehydrogenase, Alkaline phosphatase \[\>0.3\*ULN\], Total protein, Albumin \[\<0.8\*LLN/ \>1.2\*ULN\]); Renal Function (Blood urea nitrogen, Creatinine \[\>1.3\*ULN\], Uric acid \[\>1.2\*ULN\]); Electrolytes (sodium \[\<0.95\*LLN/ \>1.05\*ULN\], potassium, chloride, calcium, magnesium \[\<0.9\*LLN/ \>1.1\*ULN\], phosphate \[\<0.8\*LLN/ \>1.2\*ULN\]); Other (Glucose \[\<0.6\*LLN/ \>1.5\*ULN\]).

Number of Participants With Treatment-Emergent Adverse Events by Severity
Day 1 up to 28 days after last dose of study medication

AE = any untoward medical occurrence in participant who received study medication without regard to possibility of causal relationship. Severity was assessed as: Grade 1 (Mild); Grade 2 (Moderate); Grade 3 (Severe) = unacceptable or intolerable events, significantly interrupting usual daily activity, and requiring systemic medication therapy/other treatment; Grade 4 (Life-threatening) = events causing participant to be in imminent danger of death; Grade 5 (Death) = death related to an AE. Treatment-emergent events = between first dose of study medication and up to 28 days after last dose, that were absent before treatment or that worsened relative to pre-treatment state. A participant may be represented in more than 1 category.

Number of Participants With Treatment-Related Adverse Events (AEs) and Serious Adverse Events (SAEs)
Day 1 up to 28 days after last dose of study medication

An AE was any untoward medical occurrence attributed to study drug in a participant who received study drug. An SAE was an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly. The events which were considered treatment-related by sponsor and/or investigator were reported.

Number of Participants With Dose-Limiting Toxicities (DLT)
Baseline up to 28 days

DLT: an adverse event occurring after initiation of PD 0332991 that met any following criteria: 1) Grade 4 hematologic toxicity (platelets less than \[\<\] 25000 per microliter (mcL), absolute neutrophil count \[ANC\] \<500/mcL, hemoglobin \[Hb\] \<6.5 gram per deciliter \[g/dL\]; 2) ANC \<1000/mcL associated with documented infection or fever greater than or equal to (\>=) 38.5 degrees Celsius; 3) \>=Grade 3 non-hematologic treatment-related toxicity. In an asymptomatic participant, Grade 3 corrected QT (QTc) prolongation (\>500 millisecond) (only if persisted with repeat testing and after correction of reversible causes \[electrolyte abnormalities or hypoxia\]); and 4) Inability to receive next dose of PD 0332991 within 1 week (+/-1 day) of last dose due to lack of hematologic recovery (platelets \<50000/mcL, ANC \<1000/mcL, and Hb \<8.0 g/dL) or due to prolonged non-hematologic toxicities of \>=Grade 3 severity. Occurrence of a DLT necessitated immediate interruption of scheduled study treatment.

Maximum Administered Dose (MAD)
Baseline up to 28 days

Three new evaluable participants were to be assessed at each new dose level. The minimum time that these participants were to be followed after starting treatment was 1 cycle (28 or 21 days) before a new dose level could be opened. If none of these 3 participants experienced a DLT, the next higher dose level was to be opened on that schedule. If 1 participant developed a DLT, 3 more evaluable participants were to be enrolled at that dose level; if none of these additional 3 participants developed a DLT, the next higher dose level was to be opened on that schedule. If \>=2 participants experienced a first cycle DLT at the same dose level and schedule, that dose level was to be defined as the MAD for that schedule. No additional participants were to be entered at the MAD for that dosing schedule. DLT is defined in Outcome Measure 1.

Maximum Tolerated Dose (MTD)/Recommended Phase 2 Dose Level (RP2D)
Baseline up to 28 days

MTD was defined as the highest dose level studied for which the incidence of first cycle DLT was \<33%. Once MTD was determined, it was defined as RP2D. DLT is defined in Outcome Measure 1.

Number of Dose-Limiting Toxicities (DLTs) Categorized as Per the Nature
Baseline up to 28 days

DLT is defined in Outcome Measure 1. Hematologic (Grade 4 \[life-threatening or disabling\]) and non-hematologic (Grade 3 \[severe\], 4 \[life-threatening and disabling\], 5 \[resulting in death\]) DLTs are reported separately. A single participant may experience more than one DLT. Both treatment-related and treatment-unrelated DLT events were reported for this outcome measure.

Number of Participants With Treatment Emergent Adverse Events Categorized by Severity
Cycle 1, Cycle 2 up to 28 days after end of treatment (up to Cycle 93)

An adverse event (AE) was any untoward medical occurrence in a participant who received study drug without regard to possibility of causal relationship. Treatment-emergent are events between first dose of study drug and up to 28 days after last dose that were absent before treatment or that worsened relative to pretreatment state. For clinical description of nature (severity) of AEs, AEs were grades as: Grade 1: mild AE; Grade 2: moderate AE; Grade 3: severe AE; Grade 4: life-threatening or disabling AE; and Grade 5: death related to AE. AEs during Cycle 1 and AEs post Cycle 1 are reported separately.

Number of Participants With Treatment-Related Treatment Emergent Adverse Events
Cycle 1, Cycle 2 up to 28 days after end of treatment (up to Cycle 93)

A treatment-related AE was any untoward medical occurrence attributed to study drug in a participant who received study drug. Treatment-emergent are events between first dose of study drug and up to 28 days after last dose that were absent before treatment or that worsened relative to pretreatment state. AEs during Cycle 1 and AEs post Cycle 1 are reported separately.

Number of Participants Who Died Due to Adverse Event on the Basis of Relatedness to Study Drug
Baseline up to 30 days after end of treatment (up to Cycle 93)

An AE was any untoward medical occurrence in a participant who received study drug without regard to possibility of causal relationship. A treatment-related AE was any untoward medical occurrence attributed to study drug in a participant who received study drug. Treatment. Treatment-emergent are events between first dose of study drug and up to 28 days after last dose that were absent before treatment or that worsened relative to pretreatment state. Relatedness \[to study drug\] was assessed by the investigator (Yes/No).

Maximum Observed Plasma Concentration (Cmax) on Day 1: Single Dose
Hour 0 (pre-dose), 1, 2, 4, 7, and 10 hours post-dose on Day 1 of Cycle 1 (C1D1)
Maximum Observed Plasma Concentration (Cmax) on Day 8: Multiple Dose
Hour 0 (pre-dose), 1, 2, 4, 7, and 10 hours post-dose on Day 8 of Cycle 1 (C1D8)
Maximum Observed Plasma Concentration (Cmax) on Day 14/21 Dose-Corrected to 125 mg: Multiple Dose
Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D21 for participants receiving 125 mg (21/28 Days) and Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D14 for participants receiving 200 mg (14/21 Days)

The mean Cmax for 200 mg dose group (dose corrected to 125 mg) on Cycle 1 Day 14 (C1D14) and 125 mg dose group on Cycle 1 Day 21 (C1D21) was calculated. Only participants from 125 mg and 200 mg dose groups were reported.

Maximum Observed Plasma Concentration (Cmax) on Day 1: Food Effect
Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D1, C2D1

To determine the impact of food (specifically a high-fat meal) on PD 0332991 PK, participants were tested under fed and fasted conditions in crossover fashion. Each participant served as their own control. In this crossover fashion first dose was administered under either fed (high-fat meal) or fasted (10-hour fast) condition on Day 1 of Cycle 1 and 2. The first 6 participants were tested under fed (on C1D1) followed by fasted (on C2D1) conditions, the next 6 participants were tested under fasted (on C1D1) followed by fed (on C2D1) conditions. Only participants in PD 0332991 200 mg (14/21 days) and 125 mg (21/28 days) groups participated in food effect crossover and results are reported as per fed and fasted conditions. The high-fat meal was composed of around 800 to 1000 calories total, with fat composing around 50% of the total caloric content.

Time to Reach Maximum Observed Plasma Concentration (Tmax) on Day 1: Single Dose
Hour 0 (pre-dose), 1, 2, 4, 7, and 10 hours post-dose on Day 1 of Cycle 1 (C1D1)
Time to Reach Maximum Observed Plasma Concentration (Tmax) on Day 8: Multiple Dose
Hour 0 (pre-dose), 1, 2, 4, 7, and 10 hours post-dose on Day 8 of Cycle 1 (C1D8)
Time to Reach Maximum Observed Plasma Concentration (Tmax) on Day 14/21 Dose-Corrected to 125 mg: Multiple Dose
Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D21 for participants receiving 125 mg (21/28 Days) and Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D14 for participants receiving 200 mg (14/21 Days)

The median Tmax for 200 mg dose group (dose corrected to 125 mg) on Cycle 1 Day 14 (C1D14) and 125 mg dose group on Cycle 1 Day 21 (C1D21) was calculated. Only participants from 125 mg and 200 mg dose groups were reported.

Time to Reach Maximum Observed Plasma Concentration (Tmax) on Day 1: Food Effect
Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D1, C2D1

To determine impact of food (specifically high-fat meal) on PD 0332991 PK, participants were tested under fed and fasted conditions in crossover fashion. Each participant served as their own control. In crossover fashion first dose was administered under either fed (high-fat meal) or fasted (10-hour fast) condition on Day 1 of Cycle 1 and 2. First 6 participants were tested under fed (on C1D1) followed by fasted (on C2D1) conditions, next 6 participants were tested under fasted (on C1D1) followed by fed (on C2D1) conditions. Only participants in PD 0332991 200 mg (14/21 days) and 125 mg (21/28 days) groups participated in food effect crossover and results are reported as per fed and fasted conditions. High-fat meal was composed of around 800 to 1000 calories total, with fat composing around 50% of total caloric content.

Terminal Half-life (t½ ) on Day 1: Single Dose
Hour 0 (pre-dose), 1, 2, 4, 7, and 10 hours post-dose on Day 1 of Cycle 1 (C1D1)

Terminal half-life is the time measured for the plasma concentration to decrease by one half.

Terminal Half-life (t½ ) on Day 8: Multiple Dose
Hour 0 (pre-dose), 1, 2, 4, 7, and 10 hours post-dose on Day 8 of Cycle 1 (C1D8)

Terminal half-life is the time measured for the plasma concentration to decrease by one half.

Terminal Half-life (t½) on Day 14/21 Dose-Corrected to 125 mg: Multiple Dose
Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D21 for participants receiving 125 mg (21/28 Days) and Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D14 for participants receiving 200 mg (14/21 Days)

Terminal half-life is the time measured for the plasma concentration to decrease by one half. The mean t1/2 for 200 mg dose group (dose corrected to 125 mg) on Cycle 1 Day 14 (C1D14) and 125 mg dose group on Cycle 1 Day 21 (C1D21) was calculated. Only participants from 125 mg and 200 mg dose groups were reported.

Terminal Half-life (t½ ) on Day 1: Food Effect
Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D1, C2D1

To determine impact of food (specifically high-fat meal) on PD 0332991 PK, participants were tested under fed and fasted conditions in crossover fashion. Each participant served as their own control. In crossover fashion first dose was administered under either fed (high-fat meal) or fasted (10-hour fast) condition on Day 1 of Cycle 1 and 2. First 6 participants were tested under fed (on C1D1) followed by fasted (on C2D1) conditions, next 6 participants were tested under fasted (on C1D1) followed by fed (on C2D1) conditions. Only participants in PD 0332991 200 mg (14/21 days) and 125 mg (21/28 days) groups participated in food effect crossover and results were to be reported as per fed and fasted conditions. High-fat meal was composed of around 800 to 1000 calories total, with fat composing around 50% of total caloric content.

Area Under the Curve From Time Zero to the Last Measured Concentration (AUClast) on Day 1: Single Dose
Hour 0 (pre-dose), 1, 2, 4, 7, and 10 hours post-dose on Day 1 of Cycle 1 (C1D1)

Area under the plasma concentration time-curve from zero to the last measured concentration (AUClast).

Area Under the Curve From Time Zero to the Last Measured Concentration (AUClast) on Day 8: Multiple Dose
Hour 0 (pre-dose), 1, 2, 4, 7, and 10 hours post-dose on Day 8 of Cycle 1 (C1D8)

Area under the plasma concentration time-curve from zero to the last measured concentration (AUClast).

Area Under the Curve From Time Zero to the Last Measured Concentration (AUClast) on Day 14/21 Dose-Corrected to 125 mg: Multiple Dose
Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D21 for participants receiving 125 mg (21/28 Days) and Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D14 for participants receiving 200 mg (14/21 Days)

Area under the plasma concentration time-curve from zero to the last measured concentration (AUClast). The mean AUClast for 200 mg dose group (dose corrected to 125 mg) on Cycle 1 Day 14 (C1D14) and 125 mg dose group on Cycle 1 Day 21 (C1D21) was calculated. Only participants from 125 mg and 200 mg dose groups were reported.

Area Under the Curve From Time Zero to the Last Measured Concentration (AUClast) on Day 1: Food Effect
Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D1, C2D1

Area under the plasma concentration time-curve from zero to the last measured concentration (AUClast). To determine impact of food (specifically high-fat meal) on PD 0332991 PK, participants were tested under fed and fasted conditions in crossover fashion. Each participant served as their own control. In crossover fashion first dose was administered under either fed (high-fat meal) or fasted (10-hour fast) condition on Day 1 of Cycle 1 and 2. First 6 participants were tested under fed (on C1D1) followed by fasted (on C2D1) conditions, next 6 participants were tested under fasted (on C1D1) followed by fed (on C2D1) conditions. Only participants in PD 0332991 200 mg (14/21 days) and 125 mg (21/28 days) groups participated in food effect crossover and results are reported as per fed and fasted conditions. High-fat meal was composed of around 800 to 1000 calories total, with fat composing around 50% of total caloric content.

Area Under the Curve From Time Zero to End of the Dosing Interval [AUC(0 to Tau)] on Day 14/21 Dose-Corrected to 125 mg: Multiple Dose
Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D21 for participants receiving 125 mg (21/28 Days) and Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D14 for participants receiving 200 mg (14/21 Days)

Area under the curve from time zero to end of the dosing interval (24 hours) \[AUC (0-tau)\]. The mean AUC (0-tau) for 200 mg dose group (dose corrected to 125 mg) on Cycle 1 Day 14 (C1D14) and 125 mg dose group on Cycle 1 Day 21 (C1D21) was calculated. Only participants from 125 mg and 200 mg dose groups were reported.

Area Under the Curve From Time Zero to Extrapolated Infinite Time [AUC (0 - ∞)] on Day 1: Single Dose
Hour 0 (pre-dose), 1, 2, 4, 7, and 10 hours post-dose on Day 1 of Cycle 1 (C1D1)

AUC (0 - ∞) = Area under the plasma concentration versus time curve (AUC) from time zero (pre-dose) to extrapolated infinite time (0 - ∞). It is obtained from AUC (0 - t) plus AUC (t - ∞).

Area Under the Curve From Time Zero to Extrapolated Infinite Time [AUC (0 - ∞)] on Day 8: Multiple Dose
Hour 0 (pre-dose), 1, 2, 4, 7, and 10 hours post-dose on Day 8 of Cycle 1 (C1D8)

AUC (0 - ∞) = Area under the plasma concentration versus time curve (AUC) from time zero (pre-dose) to extrapolated infinite time (0 - ∞). It is obtained from AUC (0 - t) plus AUC (t - ∞).

Area Under the Curve From Time Zero to Extrapolated Infinite Time [AUC (0 - ∞)] on Day 1: Food Effect
Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D1, C2D1

AUC (0 - ∞) = Area under the plasma concentration versus time curve (AUC) from time zero (pre-dose) to extrapolated infinite time (0 - ∞). To determine impact of food (specifically high-fat meal) on PD 0332991 PK, participants were tested under fed and fasted conditions in crossover fashion. Each participant served as their own control. In crossover fashion first dose was administered under either fed (high-fat meal) or fasted (10-hour fast) condition on Day 1 of Cycle 1 and 2. First 6 participants were tested under fed (on C1D1) followed by fasted (on C2D1) conditions, next 6 participants were tested under fasted (on C1D1) followed by fed (on C2D1) conditions. Only participants in PD 0332991 200 mg (14/21 days) and 125 mg (21/28 days) groups participated in food effect crossover and results were to be reported as per fed and fasted conditions. High-fat meal was composed of around 800 to 1000 calories total, with fat composing around 50% of total caloric content.

Apparent Oral Clearance (CL/F) on Day 1: Single Dose
Hour 0 (pre-dose), 1, 2, 4, 7, and 10 hours post-dose on Day 1 of Cycle 1 (C1D1)

Clearance of a drug is a measure of the rate at which a drug is metabolized or eliminated by normal biological processes. Clearance obtained after oral dose (apparent oral clearance) is influenced by the fraction of the dose absorbed. Clearance was estimated from population pharmacokinetic (PK) modeling. Drug clearance is a quantitative measure of the rate at which a drug substance is removed from the blood.

Apparent Oral Clearance (CL/F) on Day 8: Multiple Dose
Hour 0 (pre-dose), 1, 2, 4, 7, and 10 hours post-dose on Day 8 of Cycle 1 (C1D8)

Clearance of a drug is a measure of the rate at which a drug is metabolized or eliminated by normal biological processes. Clearance obtained after oral dose (apparent oral clearance) is influenced by the fraction of the dose absorbed. Clearance was estimated from population pharmacokinetic (PK) modeling. Drug clearance is a quantitative measure of the rate at which a drug substance is removed from the blood.

Apparent Oral Clearance (CL/F) on Day 14/21 Dose-Corrected to 125 mg: Multiple Dose
Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D21 for participants receiving 125 mg (21/28 Days) and Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D14 for participants receiving 200 mg (14/21 Days)

Clearance of a drug is a measure of rate at which a drug is metabolized or eliminated by normal biological processes. Clearance obtained after oral dose (apparent oral clearance) is influenced by the fraction of dose absorbed. Clearance was estimated from population pharmacokinetic (PK) modeling. Drug clearance is a quantitative measure of the rate at which a drug substance is removed from the blood. The mean CL/F for 200 mg dose group (dose corrected to 125 mg) on Cycle 1 Day 14 (C1D14) and 125 mg dose group on Cycle 1 Day 21 (C1D21) was calculated. Only participants from 125 mg and 200 mg dose groups were reported.

Apparent Oral Clearance (CL/F) on Day 1: Food Effect
Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D1, C2D1

Clearance of a drug is a measure of rate at which a drug is metabolized or eliminated by normal biological processes. To determine impact of food (specifically high-fat meal) on PD 0332991 PK, participants were tested under fed and fasted conditions in crossover fashion. Each participant served as their own control. In crossover fashion first dose was administered under either fed (high-fat meal) or fasted (10-hour fast) condition on Day 1 of Cycle 1 and 2. First 6 participants were tested under fed (on C1D1) followed by fasted (on C2D1) conditions, next 6 participants were tested under fasted (on C1D1) followed by fed (on C2D1) conditions. Only participants in PD 0332991 200 mg (14/21 days) and 125 mg (21/28 days) groups participated in food effect crossover and results were to be reported as per fed and fasted conditions. High-fat meal was composed of around 800 to 1000 calories total, with fat composing around 50% of total caloric content.

Apparent Volume of Distribution (Vz/F) on Day 1: Single Dose
Hour 0 (pre-dose), 1, 2, 4, 7, and 10 hours post-dose on Day 1 of Cycle 1 (C1D1)

Volume of distribution is defined as the theoretical volume in which the total amount of drug would need to be uniformly distributed to produce the desired plasma concentration of a drug. Apparent volume of distribution after oral dose (Vz/F) is influenced by the fraction absorbed.

Apparent Volume of Distribution (Vz/F) on Day 8: Multiple Dose
Hour 0 (pre-dose), 1, 2, 4, 7, and 10 hours post-dose on Day 8 of Cycle 1 (C1D8)

Volume of distribution is defined as the theoretical volume in which the total amount of drug would need to be uniformly distributed to produce the desired plasma concentration of a drug. Apparent volume of distribution after oral dose (Vz/F) is influenced by the fraction absorbed.

Apparent Volume of Distribution (Vz/F) on Day 14/21 Dose-Corrected to 125 mg: Multiple Dose
Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D21 for participants receiving 125 mg (21/28 Days) and Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D14 for participants receiving 200 mg (14/21 Days)

Volume of distribution is defined as the theoretical volume in which the total amount of drug would need to be uniformly distributed to produce the desired plasma concentration of a drug. Apparent volume of distribution after oral dose (Vz/F) is influenced by the fraction absorbed. The mean Vz/F for 200 mg dose group (dose corrected to 125 mg) on Cycle 1 Day 14 (C1D14) and 125 mg dose group on Cycle 1 Day 21 (C1D21) was calculated. Only participants from 125 mg and 200 mg dose groups were reported.

Apparent Volume of Distribution (Vz/F) on Day 1: Food Effect
Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D1, C2D1

Volume of distribution: theoretical volume in which total amount of drug would need to be uniformly distributed to produce desired plasma concentration. To determine impact of food (specifically high-fat meal) on PD 0332991 PK, participants were tested under fed and fasted conditions in crossover fashion. Each participant served as their own control. In crossover fashion first dose was administered under either fed (high-fat meal) or fasted (10-hour fast) condition on Day 1 of Cycle 1 and 2. First 6 participants were tested under fed (on C1D1) followed by fasted (on C2D1) conditions, next 6 participants were tested under fasted (on C1D1) followed by fed (on C2D1) conditions. Only participants in PD 0332991 200 mg (14/21 days) and 125 mg (21/28 days) groups participated in food effect crossover and results were to be reported as per fed and fasted conditions. High-fat meal was composed of around 800 to 1000 calories total, with fat composing around 50% of total caloric content.

Accumulation Ratio (Rac) on Day 8: Multiple Dose
Hour 0 (pre-dose), 1, 2, 4, 7, 10, and 24 hours post-dose on C1D1 and C1D8

Rac at Day 8 = AUC (0-tau) at Day 8 divided by AUC (0-tau) at Day 1.

Accumulation Ratio (Rac) on Day 14/21 Dose-Corrected to 125 mg: Multiple Dose
Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D21 for participants receiving 125 mg (21/28 Days) and Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D14 for participants receiving 200 mg (14/21 Days)

Rac at Day 14/21 = AUC (0-tau) at Day 14/21 divided by AUC (0-tau) at Day 1. The mean Rac for 200 mg dose group (dose corrected to 125 mg) on Cycle 1 Day 14 (C1D14) and 125 mg dose group on Cycle 1 Day 21 (C1D21) was calculated. Only participants from 125 mg and 200 mg dose groups were reported.

Terminal Phase Rate Constant [Lambda (z)] on Day 1: Single Dose
Hour 0 (pre-dose), 1, 2, 4, 7, and 10 hours post-dose on Day 1 of Cycle 1 (C1D1)

Terminal phase rate constant is the absolute value of the slope of a linear regression during the terminal phase of the natural--logarithm transformed concentration--time profile.

Terminal Phase Rate Constant [Lambda (z)] on Day 8: Multiple Dose
Hour 0 (pre-dose), 1, 2, 4, 7, and 10 hours post-dose on Day 8 of Cycle 1 (C1D8)

Terminal phase rate constant is the absolute value of the slope of a linear regression during the terminal phase of the natural-logarithm transformed concentration-time profile.

Terminal Phase Rate Constant [Lambda (z)] on Day 14/21 Dose-Corrected to 125 mg: Multiple Dose
Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D21 for participants receiving 125 mg (21/28 Days) and Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D14 for participants receiving 200 mg (14/21 Days)

Terminal phase rate constant is the absolute value of the slope of a linear regression during the terminal phase of the natural-logarithm transformed concentration-time profile. The mean lambda (z) for 200 mg dose group (dose corrected to 125 mg) on Cycle 1 Day 14 (C1D14) and 125 mg dose group on Cycle 1 Day 21 (C1D21) was calculated. Only participants from 125 mg and 200 mg dose groups were reported.

Terminal Phase Rate Constant [Lambda (z)] on Day 1: Food Effect
Hour 0 (pre-dose), 1, 2, 4, 7, 10 and 24 hours post-dose on C1D1, C2D1

Terminal phase rate constant: absolute value of slope of a linear regression during terminal phase of natural-logarithm transformed concentration-time profile. To determine impact of food (specifically high-fat meal) on PD 0332991 PK, participants were tested under fed and fasted conditions in crossover fashion. Each participant served as their own control. In crossover fashion first dose was administered under either fed (high-fat meal) or fasted (10-hour fast) condition on Day 1 of Cycle 1 and 2. First 6 participants were tested under fed (on C1D1) followed by fasted (on C2D1) conditions, next 6 participants were tested under fasted (on C1D1) followed by fed (on C2D1) conditions. Only participants in PD 0332991 200 mg (14/21 days) and 125 mg (21/28 days) groups participated in food effect crossover and results were to be reported as per fed and fasted conditions. High-fat meal was composed of around 800 to 1000 calories total, with fat composing around 50% of total caloric content.

Cumulative Amount of Drug Recovered Unchanged in the Urine (Ae): Single Dose
Hour 0 (pre-dose) to 10 hours post-dose on C1D1

Ae is the cumulative amount of drug recovered unchanged in urine over the 10 hour collection interval. Cumulative amount was calculated as sum of urine drug concentration in sample volume for each collection interval. Urine PK analysis was performed only in the MTD/RP2D groups (125 mg \[21/28 Days\] and 200 mg \[14/21 Days\]).

Cumulative Amount of Drug Recovered Unchanged in the Urine (Ae): Food Effect
Hour 0 (pre-dose) to 10 hours post-dose on C1D1

The Ae is defined in Outcome Measure 42. To determine impact of food (specifically high-fat meal) on PD 0332991 PK, participants were tested under fed and fasted conditions in crossover fashion. Each participant served as their own control. In crossover fashion first dose was administered under either fed (high-fat meal) or fasted (10-hour fast) condition on Day 1 of Cycle 1 and 2. First 6 participants were tested under fed (on C1D1) followed by fasted (on C2D1) conditions, next 6 participants were tested under fasted (on C1D1) followed by fed (on C2D1) conditions. Only participants in PD 0332991 200 mg (14/21 days) and 125 mg (21/28 days) groups participated in food effect crossover and results were to be reported as per fed and fasted conditions. High-fat meal was composed of around 800 to 1000 calories total, with fat composing around 50% of total caloric content.

Percent Dose Recovered Unchanged in Urine (Percent Ae): Single Dose
Hour 0 (pre-dose) to 10 hours post-dose on C1D1

Percent of dose recovered unchanged in urine over the 10 hour collection interval=100\*(Ae divided by dose). Ae is the cumulative amount of drug recovered unchanged in urine over the 10 hour collection interval. Cumulative amount was calculated as sum of urine drug concentration in sample volume for each collection interval.

Percent Dose Recovered Unchanged (Percent Ae) in Urine: Food Effect
Hour 0 (pre-dose) to 10 hours post-dose on C1D1

The percent Ae is defined in Outcome Measure 44. To determine impact of food (specifically high-fat meal) on PD 0332991 PK, participants were tested under fed and fasted conditions in crossover fashion. Each participant served as their own control. In crossover fashion first dose was administered under either fed (high-fat meal) or fasted (10-hour fast) condition on Day 1 of Cycle 1 and 2. First 6 participants were tested under fed (on C1D1) followed by fasted (on C2D1) conditions, next 6 participants were tested under fasted (on C1D1) followed by fed (on C2D1) conditions. Only participants in PD 0332991 200 mg (14/21 days) and 125 mg (21/28 days) groups participated in food effect crossover and results were to be reported as per fed and fasted conditions. High-fat meal was composed of around 800 to 1000 calories total, with fat composing around 50% of total caloric content.

Number of Participants With Best Response
Baseline up to end of treatment, assessed at C1D1, C1D8, C1D15, C1D22, thereafter Day 1, 8, 15, and 22 of every other cycle up to end of treatment (up to Cycle 93)

Number of participants with best response. Complete response (CR): disappearance of all target and non-target lesions. Partial Response (PR): \>=30% decrease in sum of longest diameter (LD) of lesions taking as reference baseline sum LD and no unequivocal progression in non-target lesions. Progressive disease (PD): \>=20% increase in sum of LD of lesions taking as a reference smallest sum of the LD since treatment start, or the appearance of \>=1 new lesion or unequivocal progression of existing non-target lesions. Stable disease (SD): neither shrinkage for PR nor increase for PD taking as reference smallest sum of LD since treatment start. SD was assessed following the first 2 cycles of treatment (\>=2 cycles), 4 cycles of treatment (\>=4 cycles), and 10 cycles of treatment (\>=10 cycles). Participants may be reported in more than 1 category of SD. Confirmed responses are those that persist on repeat imaging study at least 4 weeks after initial documentation of response.

Inhibition of Cyclin-dependent Kinases 4 and 6 (Cdk4/6) Based on Phosphorylated Retinoblastoma (p-Rb) in Tumor Tissue
Baseline, C1D1, C1D8, C1D15, C1D22, thereafter Day 1, 8, 15, and 22 of every other cycle up to end of treatment (up to Cycle 93)

Phosphorylation of the retinoblastoma (Rb) protein by Cdk4/6 is typically required for human cancer cell proliferation. Tumor biopsies were to be performed, to demonstrate inhibition of Cdk4/6 based on reduction in phosphorylated Rb (p-Rb) in tumor tissue and p-Rb levels (fold decrease) were to be reported.

Correlation of Cyclin-dependent Kinases 4 and 6 (Cdk4/6) With PD 0322991 Dose
Baseline, C1D1, C1D8, C1D15, C1D22, thereafter Day 1, 8, 15, and 22 of every other cycle up to end of treatment (up to Cycle 93)

Phosphorylation of the retinoblastoma (Rb) protein by Cdk4/6 is typically required for human cancer cell proliferation. Tumor biopsies were to be performed, to demonstrate inhibition of Cdk4/6 based on reduction in phosphorylated Rb (p-Rb) in tumor tissue, in correlation with respect to PD 0322991 dose.

Correlation of Cyclin-dependent Kinases 4 and 6 (Cdk4/6) With Exposure
Baseline, C1D1, C1D8, C1D15, C1D22, thereafter Day 1, 8, 15, and 22 of every other cycle up to end of treatment (up to Cycle 93)

Phosphorylation of the retinoblastoma (Rb) protein by Cdk4/6 is typically required for human cancer cell proliferation. Tumor biopsies were to be performed, to demonstrate inhibition of Cdk4/6 based on reduction in phosphorylated Rb (p-Rb) in tumor tissue, in correlation with PD 0322991 exposure.

Correlation of Cyclin-dependent Kinases 4 and 6 (Cdk4/6) With Tumor Response
Baseline, C1D1, C1D8, C1D15, C1D22, thereafter Day 1, 8, 15, and 22 of every other cycle up to end of treatment (up to Cycle 93)

Phosphorylation of the retinoblastoma (Rb) protein by Cdk4/6 is typically required for human cancer cell proliferation. Tumor biopsies were to be performed, to demonstrate inhibition of Cdk4/6 based on reduction in phosphorylated Rb (p-Rb) in tumor tissue, in correlation with tumor response.

Secondary Endpoints

Progression-Free Survival (PFS) Based on Blinded Independent Central Review (BICR): Up to Primary Completion Date
Randomization up to 65 months
Percentage of Participants With Objective Response (OR) Based on Investigator Assessment: Up to Primary Completion Date
Randomization up to 65 months
Percentage of Participants With Objective Response (OR) Based on Investigator Assessment (Participants With Measurable Disease at Baseline): Up to Primary Completion Date
Randomization up to 65 months
Unlock Study Endpoints

Study Design & Arms

AllocationRANDOMIZED
MaskingQUADRUPLE
ModelPARALLEL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
Palbociclib + LetrozoleEXPERIMENTALPalbociclib, 125mg, orally once daily on Day 1 to Day 21 of every 28-day cycle followed by 7 days off treatment in combination with Letrozole, 2.5mg, orally once daily (continuously)
Placebo + LetrozoleACTIVE_COMPARATORPlacebo, 125mg, orally once daily on Day 1 to Day 21 of every 28-day cycle followed by 7 days off treatment in combination with Letrozole, 2.5mg, orally once daily (continuously).
PD-0332991 + LetrozoleEXPERIMENTALPD-0332991, 125mg, orally once daily on Day 1 to Day 21 of every 28-day cycle followed by 7 days off treatment in combination with Letrozole, 2.5mg, orally once daily (continuously).
Single-agent PD-0332991EXPERIMENTALPhase 1 Part 1
PD-0332991 in combination with letrozoleEXPERIMENTALPhase 1 Part 2
PD-0332991 with letrozoleEXPERIMENTALPhase 2
PD-0332991EXPERIMENTAL -

Interventions

NameTypeDescription
PalbociclibDRUGPalbociclib, 125mg, orally once daily on Day 1 to Day 21 of every 28-day cycle followed by 7 days off treatment
LetrozoleDRUGLetrozole, 2.5mg, orally once daily (continuously)
PlaceboDRUGPlacebo, 125mg, orally once daily on Day 1 to Day 21 of every 28-day cycle followed by 7 days off treatment
PD-0332991DRUGPD-0332991, 125mg, orally once daily on Day 1 to Day 21 of every 28-day cycle followed by 7 days off treatment
Unlock Study Design Details

Eligibility Criteria

Age Range18 Years to 70 Years
SexFEMALE
Healthy VolunteersNo
Study Sites54

Inclusion Criteria: * Adult Asian women with locoregionally recurrent or metastatic disease not amenable to curative therapy * Confirmed diagnosis of ER positive breast cancer * No prior systemic anti-cancer therapy for advanced ER+ disease * Postmenopausal women * Measurable disease as per Respons...

Countries:ChinaHong KongSingaporeTaiwanThailandUnited StatesAustraliaBelgiumCanadaCzechiaFranceGermanyHungaryIrelandItalyJapanPolandRussiaSouth KoreaSpainUkraineUnited Kingdom
Unlock Eligibility Criteria

Recent Changes (Last 90 Days)

MEDIUMJun 14, 2026NCT02297438TRIAL_REMOVED: changed
MEDIUMJun 14, 2026NCT02297438TRIAL_REMOVED: changed
MEDIUMJun 14, 2026NCT02297438TRIAL_REMOVED: changed

Frequently asked questions about PD-0332991

What is PD 0332991 used for?

PD 0332991, also known as palbociclib, is an investigational small molecule being studied for the treatment of breast cancer, including advanced breast cancer and metastatic breast cancer. It is also being evaluated in Ewing sarcoma and other neoplasms. The drug is in Phase 2 clinical development and is not yet approved.

What does PD 0332991 target?

PD 0332991 targets cyclin-dependent kinases (CDKs), specifically CDK4 and CDK6, as indicated by its target class of -ciclib (CDK). It is a CDK4/6 inhibitor being developed as an oral therapy for hormone receptor-positive, HER2-negative breast cancer.

Who makes PD 0332991?

PD 0332991 is being developed by Pfizer, Inc., a biopharmaceutical company traded on the New York Stock Exchange under the ticker symbol PFE. The drug is also known as palbociclib and is currently in Phase 2 clinical trials for oncology indications.

What phase is PD 0332991 in?

PD 0332991 is in Phase 2 clinical development. It is an investigational drug and has not received FDA approval. The compound is being studied across multiple oncology indications, including advanced breast cancer and Ewing sarcoma, with several trials already completed.

What clinical trials is PD 0332991 in?

PD 0332991 has been studied in several clinical trials, including NCT00141297, a Phase 1 study in advanced cancer; NCT01684215, a Phase 2 study in Japanese patients with advanced solid tumors or breast cancer; NCT01942135 (PALOMA-3), a Phase 3 study in metastatic breast cancer; and NCT03447132, a Phase 3 study in operable breast cancer.

Is PD 0332991 the same as palbociclib?

Yes, PD 0332991 is the same as palbociclib. The drug is known by both names, with palbociclib being the generic name and PD 0332991 the research code. Pfizer is developing this CDK4/6 inhibitor for breast cancer and other oncology indications.