PIK3CA-Related Overgrowth Spectrum Clinical Trials

• If pre/perimenopausal women and men treatment with luteinizing hormone-releasing hormone (LHRH) agonist therapy beginning at least 2 weeks prior to Day 1 of Cycle 1

• Histologically or cytologically confirmed adenocarcinoma of the breast that is locally advanced or metastatic and is not amenable to surgical or radiation therapy with curative intent

• Documented HR +/ HER2- tumor according to American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guidelines

• Confirmation of biomarker eligibility: detection of specified mutation(s) of PIK3CA via specified test

• Disease progression after or during treatment with a combination of CDK4/6i and endocrine therapy: \<= 2 prior lines of systemic therapy in mBC setting; CDK4/6i based therapy does not need to be the last one received prior study entry; one line of chemotherapy in mBC setting allowed

• Measurable or evaluable disease per Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST v1.1)

• Participants for whom endocrine-based therapy is recommended and treatment with cytotoxic chemotherapy is not indicated at time of entry into the study, as per national or local treatment guidelines

• Eastern Cooperative Oncology Group (ECOG) Performance Status of 0, 1, or 2

• Life expectancy of \> 6 months

• Adequate hematologic and organ function prior to initiation of study treatment