Study: NCT06065748

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Giredestrant
Description: Giredestrant 30 milligrams (mg) orally (PO) once a day (QD) on Days 1-28 of each 28-day cycle until progressive disease (PD) or unacceptable toxicity.

Intervention type: DRUG
Group type: ACTIVE_COMPARATOR
Intervention: Fulvestrant
Description: Fulvestrant 500 mg intramuscularly (IM) on Days 1 and 15 of Cycle 1 and on Day 1 of each subsequent 28-day cycle until PD or unacceptable toxicity.

Intervention type: DRUG
Group type: ACTIVE_COMPARATOR
Intervention: Abemaciclib
Description: If chosen by the investigator as the CDK4/6i, participants will receive abemaciclib 150 mg PO twice per day (BID) on Days 1-28 of each 28-day cycle until PD or unacceptable toxicity.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Abemaciclib
Description: If chosen by the investigator as the CDK4/6i, participants will receive abemaciclib 150 mg PO twice per day (BID) on Days 1-28 of each 28-day cycle until PD or unacceptable toxicity.

Intervention type: DRUG
Group type: ACTIVE_COMPARATOR
Intervention: Palbociclib
Description: If chosen by the investigator as the CDK4/6i, participants will receive palbociclib 125 mg PO QD on Days 1-21 of each 28-day cycle until PD or unacceptable toxicity.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Palbociclib
Description: If chosen by the investigator as the CDK4/6i, participants will receive palbociclib 125 mg PO QD on Days 1-21 of each 28-day cycle until PD or unacceptable toxicity.

Intervention type: DRUG
Group type: ACTIVE_COMPARATOR
Intervention: Ribociclib
Description: If chosen by the investigator as the CDK4/6i, participants will receive ribociclib 600 mg PO QD on Days 1-21 of each 28-day cycle until PD or unacceptable toxicity.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: Ribociclib
Description: If chosen by the investigator as the CDK4/6i, participants will receive ribociclib 600 mg PO QD on Days 1-21 of each 28-day cycle until PD or unacceptable toxicity.

Intervention type: DRUG
Group type: ACTIVE_COMPARATOR
Intervention: LHRH Agonist
Description: Only pre/perimenopausal female participants and male participants will receive a luteinizing hormone-releasing hormone (LHRH) agonist locally approved for use in breast cancer on Day 1 of each 28-day treatment cycle.

Intervention type: DRUG
Group type: EXPERIMENTAL
Intervention: LHRH Agonist
Description: Only pre/perimenopausal female participants and male participants will receive a luteinizing hormone-releasing hormone (LHRH) agonist locally approved for use in breast cancer on Day 1 of each 28-day treatment cycle.

Intervention type: DIAGNOSTIC_TEST
Group type: ACTIVE_COMPARATOR
Intervention: FoundationOne Liquid CDx Assay (F1LCDx)
Description: F1LCDx is a next-generation sequencing (NGS)-based in vitro diagnostic test that detects and analyses genomic alterations in circulating cell-free DNA (cfDNA) isolated from plasma derived from the anti-coagulated peripheral whole blood of cancer patients. It will be used to determine the eligibility of participants requiring confirmation of ESR1 mutation status (mutation detected \[ESR1m\] vs. no mutation detected \[ESR1nmd\]).

Intervention type: DIAGNOSTIC_TEST
Group type: EXPERIMENTAL
Intervention: FoundationOne Liquid CDx Assay (F1LCDx)
Description: F1LCDx is a next-generation sequencing (NGS)-based in vitro diagnostic test that detects and analyses genomic alterations in circulating cell-free DNA (cfDNA) isolated from plasma derived from the anti-coagulated peripheral whole blood of cancer patients. It will be used to determine the eligibility of participants requiring confirmation of ESR1 mutation status (mutation detected \[ESR1m\] vs. no mutation detected \[ESR1nmd\]).