Study on Giredestrant and Palbociclib vs. Letrozole and Palbociclib for Advanced or Metastatic Breast Cancer

Inclusion Criteria

• Women who are premenopausal or perimenopausal and men must receive approved hormone therapy during the study.
• Have advanced or metastatic breast cancer that cannot be cured.
• Cancer must be estrogen receptor-positive and HER2-negative.
• If both breasts have cancer, both must be estrogen receptor-positive and HER2-negative, or the metastases must be confirmed as such.
• No previous systemic anti-cancer treatment for advanced or metastatic cancer.
• Cancer returned after early-stage treatment, with at least 24 months of hormone therapy without progression and a disease-free period of over 12 months after treatment.
• Have measurable cancer or bone-only disease with at least one bone lesion that can be tracked.
• Be in good overall health with a performance status of 0 or 1.
• Have adequate organ function.

Exclusion Criteria

• Cancer returned during or within 12 months after previous treatment with any CDK4/6 inhibitor.
• Previous treatment with a selective estrogen receptor degrader (SERD).
• Received any investigational therapy within 28 days before starting the study.
• Use of strong CYP3A inhibitors or inducers within 14 days or 5 drug elimination half-lives before the study.
• Have advanced cancer spread that could cause life-threatening complications soon.
• Have uncontrolled or symptomatic cancer spread to the brain or spinal fluid.
• Have active heart disease or a history of heart problems.
• Are pregnant or breastfeeding.