A Study Evaluating the Efficacy and Safety of Giredestrant Combined With Palbociclib Compared With Letrozole Combined With Palbociclib in Participants With Estrogen Receptor-Positive, HER2-Negative Locally Advanced or Metastatic Breast Cancer (persevERA Breast Cancer)

To join this study, your breast cancer must be hormone-sensitive (ER-positive) but not HER2-positive, and it should be advanced or have spread. If you're a woman who hasn't gone through menopause or you're a man, you’ll need to be taking special hormone medicine (LHRH agonist) throughout the study. You shouldn't have had any other systemic cancer treatment for your advanced disease before this study.

Your body should be generally healthy enough to take part, and your cancer must be visible enough on scans for doctors to measure its progress. If you've previously had a similar cancer treatment called a CDK4/6 inhibitor for early-stage breast cancer and your cancer came back during or soon after, you wouldn't be able to join. Also, if your cancer has spread aggressively to major organs and is causing severe problems, this study might not be suitable.

If you join this study, you'll be randomly assigned to receive one of two treatment combinations: either Giredestrant plus Palbociclib, or Letrozole plus Palbociclib. You won't know which combination you're getting, and neither will your doctors (this is called 'double-blind'). You'll take these medications as pills each day, as instructed by the study team.

You'll have regular visits to the clinic for check-ups, blood tests, and scans to see how you're doing and how the treatment is working. These visits will continue for as long as you're taking the study medication. After you stop the study medication, you'll have follow-up appointments to monitor your health. The total time you're involved in the study can vary, but it will involve taking medication daily and attending regular hospital visits and check-ups for an extended period.