A Study to Learn About the Study Medicine Called Vepdegestrant (ARV-471, PF-07850327) in People With ER+/HER2- Advanced Breast Cancer in China

Percentage of participants with objective response based assessment of confirmed complete response (CR) or confirmed partial response (PR) according to Response Evaluation Criteria in Solid Tumors (RECIST). Confirmed responses are those that persist on repeat imaging study at least 4 weeks after initial documentation of response.

Per RECIST v1.1: CR was defined as complete disappearance of all target lesions and non-target disease, with the exception of nodal disease. All nodes, both target and non-target, must decrease to normal (short axis <10 mm). No new lesions. PR was defined as >=30% decrease under baseline of Percentage of participants with objective response based assessment of complete response (CR) or partial response (PR) according to Response Evaluation Criteria in Solid Tumors (RECIST).

Percent of participants with confirmed complete response (CR), partial response (PR) or stable disease (SD) for at least 24 weeks on study according to RECIST.

Per RECIST v1.1: CR was defined as complete disappearance of all target lesions and non-target disease, with the exception of nodal disease. All nodes, both target and non-target, must decrease to normal (short axis <10 mm). No new lesions. PR was defined as >=30% decrease under baseline of the sum of diameters of all target lesions. The short axis was used in the sum for target nodes, while the longest diameter was used in the sum for all other target lesions. No unequivocal progression of non-target disease. No new lesions. SD was defined as not qualifying for CR, PR, Progressive Disease (PD).

DOR: time from date of first documented response (CR or PR) to first documented progression or death due to underlying cancer. RECIST V1.1, a) CR: disappearance of all lesions; any pathological lymph nodes (TLs) or non-pathological (non-TLs) must have reduction in short axis to <10 mm; normalization of tumor marker level for non-TLs; b) PR: >=30% decrease in sum of diameter (dia) of all TLs, referring baseline sum of dia; c) PD: >=20% increase in sum of diameter of all measured target lesions taking as reference smallest sum of diameter of all target lesions recorded at or after baseline, sum must also be absolute increase of >=5 mm. Unequivocal progression of existing non-target lesions. Appearance of at least 1 new lesion. If a participant with a CR or PR had no PD or death due to underlying cancer, participants was censored at date of last adequate tumor assessment.

To identify biomarkers (ESR1 mutation) of complete response and progression if occurs

Criteria for notable ECG values were as follow: QT interval (in millisecond [msec]) new (newly occurring post-baseline value) greater than (>) 450, 480, 500, increase from baseline >30, increase from baseline >60; corrected QT interval by Fredericia formula (QTcF) in msec new (newly occurring post-baseline value) > 450, 480, 500, increase from baseline >30, increase from baseline >60; corrected QT interval by Bazett's formula (QTcB) in msec new (newly occurring post-baseline value) > 450, 480, 500, increase from baseline >30, increase from baseline >60; heart rate in bpm new (newly occurring post-baseline value) <60 and >100.

Hemoglobin (HGB),hematocrit,erythrocytes (ery.),HDL cholesterol (chl.)<0.8*lower limit of normal(LLN);reticulocytes (ret.), ret./ery. (%)<0.5*LLN,>1.5*upper limit of normal (ULN);ery. mean corpuscular (EMC) volume,EMC HGB,EMC HGB

Vital signs (temperature, respiratory rate, pulse, systolic and diastolic blood pressure) were obtained with participant in the seated position, after having sat calmly for at least 5 minutes. Clinical significance of vital signs was determined at the investigator's discretion.

Counts of participants who had treatment-emergent adverse events (TEAEs), defined as newly occurring or worsening after first dose. Relatedness to [study drug] was assessed by the investigator. Participants with multiple occurrences of an AE within a category were counted once within the category. An adverse event (AE) was any untoward medical occurrence in a participant who received study drug without regard to possibility of causal relationship. As per CTCAE version 4, Grade 1= mild AE; Grade 2= moderate AE; Grade 3= severe AE; Grade 4= life-threatening or disabling AE; Grade 5= death related to an AE.

Time at which Cmax occurred

Area under the concentration-time profile from time zero to the time of the last quantifiable concentration (Clast)

ARV-473 to ARV-471 ratio for Cmax

Area under the concentration-time profile from time zero extrapolated to infinite time

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 volume of distribution

Terminal half-life

Time to Reach Maximum Observed Plasma Concentration

ARV-473 to ARV-471 ratio for Cmax

Accumulation ratio based on AUC (observed)

Effective half-life (t½eff) based on accumulation ratio

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.

Terminal half-life