A Study to Learn About Vepdegestrant When Given With PF-07220060 to People With Advanced or Metastatic Breast Cancer.

Dose Limiting Toxicities (DLTs) rate for Vepdegestrant in combination with PF-07220060, estimated based on data from DLT-evaluable participants during the DLT observation period (Cycle 1).

Objective response (OR) refers to confirmed complete response (CR) or partial response (PR) according to Response Evaluation Criteria in Solid Tumor (RECIST) version 1.1. as determined by investigator assessment.

An adverse event (AE) is any untoward medical occurrence in a participant, temporally associated with the use of study treatment, whether or not considered related to the study treatment. A severe adverse event (SAE) is any untoward medical occurrence that, at any dose: resulted in death; required inpatient hospitalization or prolongation of existing hospitalization; was life-threatening; resulted in persistent or significant disability/ incapacity; congenital anomaly/birth defect and other important medical events. A treatment-related AE is any untoward medical occurrence attributed to study drug in a participant who received study drug.

AEs were graded by the investigator according to the CTCAE version 5.0 and coded using MedDRA were reported. Grade 1=mild; Grade 2=moderate; Grade 3=severe; Grade 4=life-threatening or disabling; and Grade 5=death.

Blood samples were collected for the analysis of the following hematology and coagulation parameters: hemoglobin [g/L], platelets, leukocytes, neutrophils, lymphocytes, monocytes, eosinophils and basophils [10^9/L]; partial thromboplastin time prolonged and prothrombin time [seconds]; international normalized ratio increased. Number of participants with hematological and coagulation abnormalities by grade as per Common Terminology Criteria for Adverse Events (CTCAE version 5.0) were reported. Grade 1=mild; Grade 2=moderate; Grade 3=severe; Grade 4=life-threatening or disabling; and Grade 5=death. For laboratory tests without CTCAE grade definitions, results will be categorized as normal, abnormal, or not done.

Blood samples were collected for analysis of clinical chemistry parameters. These included: alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, [international unit per liter (IU/L)] ; Lipase and amilase [IU/L] (limited to cycle1 only); Albumin, bilirubin, urea ,calcium, creatinine, glucose, magnesium, phosphate, uric acid chloride, potassium and sodium [millimol per liter (mmol/L)]; eGFR [milliliter per minute (ml/min)]. Number of participants with hematological and coagulation abnormalities by grade as per Common Terminology Criteria for Adverse Events (CTCAE version 5.0) were reported. Grade 1=mild; Grade 2=moderate; Grade 3=severe; Grade 4=life-threatening or disabling; Grade 5=death. For laboratory tests without CTCAE grade definitions, results will be categorized as normal, abnormal, or not done.

The following ECG parameters were analyzed and changes from baseline were assessed : heart rate, PR interval, QT interval, QRS interval and QT interval corrected using Fridericia's formula (QTcF).

"An adverse event (AE) is any untoward medical occurrence in a participant, temporally associated with the use of study treatment, whether or not considered related to the study treatment. A severe adverse event (SAE) is any untoward medical occurrence that, at any dose: resulted in death; required inpatient hospitalization or prolongation of existing hospitalization; was life-threatening; resulted in persistent or significant disability/ incapacity; congenital anomaly/birth defect and other important medical events. A treatment-related AE is any untoward medical occurrence attributed to study drug in a participant who received study drug.

AEs were graded by the investigator according to the CTCAE version 5.0 and coded using MedDRA where reported. Grade 1=mild; Grade 2=moderate; Grade 3=severe; Grade 4=life-threatening or disabling; and Grade 5=death."

Blood samples were collected for the analysis of following hematology and coagulation parameters: hemoglobin [g/L], platelets, leukocytes, neutrophils, lymphocytes, monocytes, eosinophils and basophils [10^9/L]; partial thromboplastin time prolonged and prothrombin time [seconds]; international normalized ratio increased. Number of participants with hematological and coagulation abnormalities by grade as per Common Terminology Criteria for Adverse Events (CTCAE version 5.0) were reported. Grade 1=mild; Grade 2=moderate; Grade 3=severe; Grade 4=life-threatening or disabling; and Grade 5=death. For laboratory tests without CTCAE grade definitions, results will be categorized as normal, abnormal, or not done.

Blood samples were collected for analysis of clinical chemistry parameters. These included: alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, [international unit per liter (IU/L)] ; Lipase and amilase [IU/L] (limited to cycle1 only); Albumin, bilirubin, urea ,calcium, creatinine, glucose, magnesium, phosphate, uric acid chloride, potassium and sodium [millimol per liter (mmol/L)]; eGFR [milliliter per minute (ml/min)]. Number of participants with hematological and coagulation abnormalities by grade as per Common Terminology Criteria for Adverse Events (CTCAE version 5.0) were reported. Grade 1=mild; Grade 2=moderate; Grade 3=severe; Grade 4=life-threatening or disabling; and Grade 5=death. For laboratory tests without CTCAE grade definitions, results will be categorized as normal, abnormal, or not done.

Following ECG parameters were analyzed and changes from baseline were assessed: heart rate , PR interval, QT interval, QRS interval and QT interval corrected using Fridericia's formula (QTcF).

Objective response (OR) refers to confirmed complete response (CR) or partial response (PR) according to Response Evaluation Criteria in Solid Tumor (RECIST) version 1.1. as determined by investigator assessment.

Duration of Response (DoR) is defined for participants with confirmed OR (CR or PR) as the time from the first documentation of OR to the first documentation of objective tumor progression or to death due to any cause, whichever occurs first.

Clinical Benefit Response (CBR) is defined as the proportion of participants with Best Overall Response of confirmed CR or PR at any time, or Stable Disease (SD) ≥24 weeks

Progression Free Survival (PFS) is defined as the time from the date of first dose of study interventions to the date of first documentation of PD or death due to any cause, whichever occurs first.

To evaluate the plasma exposure of vepdegestrant, ARV-473, and PF-07220060 when vepdegestrant and PF-07220060 are given in combination.

Steady-state Cmax (maximum observed serum concentration of drug [Micrograms per milliliter]) of vepdegestrant, ARV-473, and PF-07220060.

Steady-state Tmax (time taken (in hours) to reach the maximum serum drug concentration) of vepdegestrant, ARV-473, and PF-07220060.

Steady-state AUClast (Area under the plasma concentration time-curve from zero to the last measured concentration (AUClast) of vepdegestrant, ARV-473, and PF-07220060.

To assess changes from baseline levels in plasma circulating tumor DNA (ctDNA) with treatment and to evaluate potential predictability of their associations with clinical outcomes.