VERITAC-2: The purpose of this study is to learn about the safety and effects of a type of hormone treatment (called vepdegestrant) compared to existing hormone treatment (called fulvestrant) in people with advanced ER+, HER2- advanced breast cancer whose cancer has progressed after previous endocrine based treatmentA Phase 3, Randomized, Open-Labe, Multicenter Trial of ARV-471 (PF-07850327) vs Fulvestrant in Participants with Estrogen Reeptor-Positive, HER2-Negative Advanced Breast Cancer Whose Disease Progressed After Prior Endocrine Based Treatment for Advanced Disease

Inclusion

• Adult participants with loco-regional recurrent or metastatic breast disease not amenable to surgical resection or radiation therapy
• Confirmed diagnosis of ER+/HER2- breast cancer
• Prior therapies for locoregional recurrent or metastatic disease must fulfill all the following criteria:
• One line of CDK4/6 inhibitor therapy in combination with endocrine therapy. Only one line of CDK4/6 inhibitor is allowed in any setting.
• ≤ 1 endocrine therapy in addition to CDK4/6 inhibitor with ET
• Most recent endocrine treatment duration must have been given for ≥6 months prior to disease progression. This may be the endocrine treatment component of the CDK4/6 inhibitor line of therapy.
• Radiological progression during or after the last line of therapy.
• Measurable disease evaluable per Response Evaluation Criterion in Solid Tumors (RECIST) v.1.1 or non-measurable bone-only disease
• Eastern Cooperative Oncology Group (ECOG) performance status 0-1
• Participants should be willing to provide blood and tumor tissue