A Study of Samuraciclib in Combination With Fulvestrant in Metastatic or Locally Advanced Breast Cancer in Adult Participants

Prior treatment

• Participants with any other active malignancy within 3 years prior to enrollment, except for adequately treated basal cell or squamous cell skin cancer, or carcinoma in situ of the cervix.
• Any current or prior central nervous system metastases, carcinomatous meningitis, or leptomeningeal disease.

Other illness

• Inflammatory breast cancer.
• More than 1 line of endocrine treatment for locally advanced or metastatic disease treatment.
• Clinically significant cardiovascular disease.

Other

• Inadequate hepatic, renal, and bone marrow function.
• Pregnant or breastfeeding women.

• Histologically confirmed diagnosis of ER-positive, HER2-negative locally advanced or metastatic breast cancer.
• Documented objective disease progression while on or within 6 months after the end of the most recent therapy.
• Received prior AI in combination with a CDK4/6i as the last therapy
• Known TP53 mutation status.
• Participants must have measurable disease or bone only disease as defined by Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1.
• Pre/peri-menopausal participants must have commenced treatment with a luteinizing hormone-releasing hormone (LHRH) agonist at least 4 weeks prior to first dose of study intervention.
• Eastern Cooperative Oncology Group (ECOG) performance status ≤1 with no deterioration over the past 2 weeks.
• Expected life expectancy of \>12 weeks in the judgement of the treating investigator.