Study on Abemaciclib Plus Fulvestrant vs. Placebo Plus Fulvestrant in Previously Treated Breast Cancer

Inclusion Criteria

• Have HR+, HER2- advanced or metastatic breast cancer.
• Show evidence of cancer progression or return:
  • While on a CDK4/6 inhibitor with an aromatase inhibitor as initial treatment for advanced cancer, or
  • During or after treatment with a CDK4/6 inhibitor plus hormone therapy for early-stage cancer.
• Be suitable for hormone therapy treatment.
• If female, be postmenopausal naturally, surgically, or through ovarian suppression.
• Have measurable or non-measurable cancer according to specific criteria.
• Have a performance status of 0 or 1, indicating full activity or some restriction in strenuous activities.
• Have adequate kidney, blood, and liver function.
• Be able to swallow pills.

Exclusion Criteria

• Have severe organ involvement, cancer spread to the lungs, or cancer in the brain or spinal fluid.
• Have untreated or symptomatic cancer spread to the brain.
• Have received any cancer treatment between cancer return/progression and study screening.
• Have had more than one treatment for advanced or metastatic cancer.
• Have had chemotherapy for metastatic breast cancer.
• Have previously been treated with fulvestrant or certain investigational hormone therapies, or inhibitors targeting specific cancer growth pathways.