{"groups":[{"description":"Participants were randomized to receive vepdegestrant 200 milligrams (mg) orally, once daily on Days 1 to 28 of each 28-day cycle. Participants continued to receive assigned treatment until objective disease progression, unacceptable toxicity, death, participant refused further treatment, or one of the other reasons for treatment discontinuation per protocol was met.","id":"FG000","title":"Vepdegestrant (ARV-471)"},{"description":"Participants were randomized to receive fulvestrant 500 mg, intramuscularly (injection) on Days 1 and 15 of Cycle 1 and then on Day 1 of each cycle starting from Cycle 2 Day 1, where 1 cycle = 28 days. Participants continued to receive assigned treatment until objective disease progression, unacceptable toxicity, death, participant refused further treatment, or one of the other reasons for treatment discontinuation per protocol was met.","id":"FG001","title":"Fulvestrant"}],"periods":[{"dropWithdraws":[{"reasons":[{"groupId":"FG000","numSubjects":"1"},{"groupId":"FG001","numSubjects":"4"}],"type":"Randomized but not treated"},{"reasons":[{"groupId":"FG000","numSubjects":"7"},{"groupId":"FG001","numSubjects":"2"}],"type":"Adverse Event"},{"reasons":[{"groupId":"FG000","numSubjects":"2"},{"groupId":"FG001","numSubjects":"0"}],"type":"Death"},{"reasons":[{"groupId":"FG000","numSubjects":"2"},{"groupId":"FG001","numSubjects":"3"}],"type":"Physician Decision"},{"reasons":[{"groupId":"FG000","numSubjects":"189"},{"groupId":"FG001","numSubjects":"209"}],"type":"Progressive disease"},{"reasons":[{"groupId":"FG000","numSubjects":"2"},{"groupId":"FG001","numSubjects":"0"}],"type":"Protocol Violation"},{"reasons":[{"groupId":"FG000","numSubjects":"9"},{"groupId":"FG001","numSubjects":"7"}],"type":"Withdrawal by Subject"},{"reasons":[{"groupId":"FG000","numSubjects":"5"},{"groupId":"FG001","numSubjects":"9"}],"type":"Global deterioration of health status"},{"reasons":[{"groupId":"FG000","numSubjects":"0"},{"groupId":"FG001","numSubjects":"1"}],"type":"Other"},{"reasons":[{"groupId":"FG000","numSubjects":"96"},{"groupId":"FG001","numSubjects":"76"}],"type":"Ongoing"}],"milestones":[{"achievements":[{"groupId":"FG000","numSubjects":"313"},{"groupId":"FG001","numSubjects":"311"}],"type":"STARTED"},{"achievements":[{"groupId":"FG000","numSubjects":"312"},{"groupId":"FG001","numSubjects":"307"}],"type":"Treated"},{"achievements":[{"groupId":"FG000","numSubjects":"0"},{"groupId":"FG001","numSubjects":"0"}],"type":"COMPLETED"},{"achievements":[{"groupId":"FG000","numSubjects":"313"},{"groupId":"FG001","numSubjects":"311"}],"type":"NOT COMPLETED"}],"title":"Treatment"},{"dropWithdraws":[{"reasons":[{"groupId":"FG000","numSubjects":"43"},{"groupId":"FG001","numSubjects":"35"}],"type":"Death"},{"reasons":[{"groupId":"FG000","numSubjects":"0"},{"groupId":"FG001","numSubjects":"1"}],"type":"Lost to Follow-up"},{"reasons":[{"groupId":"FG000","numSubjects":"1"},{"groupId":"FG001","numSubjects":"2"}],"type":"Withdrawal by Subject"},{"reasons":[{"groupId":"FG000","numSubjects":"161"},{"groupId":"FG001","numSubjects":"186"}],"type":"Ongoing"}],"milestones":[{"achievements":[{"comment":"Participants who discontinued treatment could enter the follow-up.","groupId":"FG000","numSubjects":"205"},{"comment":"Participants who discontinued treatment could enter the follow-up.","groupId":"FG001","numSubjects":"224"}],"type":"STARTED"},{"achievements":[{"groupId":"FG000","numSubjects":"0"},{"groupId":"FG001","numSubjects":"0"}],"type":"COMPLETED"},{"achievements":[{"groupId":"FG000","numSubjects":"205"},{"groupId":"FG001","numSubjects":"224"}],"type":"NOT COMPLETED"}],"title":"Follow-up"}],"preAssignmentDetails":"Results are reported at primary completion date (31 January 2025). Remaining results will be reported on completion of analysis at study completion date.","recruitmentDetails":"Participants with estrogen receptor (ER) positive, human epidermal growth factor receptor 2 negative (HER2-) unresectable locoregional recurrent or metastatic breast cancer (mBC) not amenable to radiotherapy with curative intent who progressed after prior endocrine based treatment(s) for advanced disease were included in this study."}