Placerville

Researchers are evaluating the safety and effectiveness of a drug called PF-07220060 combined with letrozole compared to other approved treatments (palbociclib, ribociclib, or abemaciclib with letrozole) in adults with breast cancer that is hormone receptor-positive and HER2-negative. This cancer has spread locally or to other parts of the body and has not been treated with systemic anti-cancer therapy for advanced or metastatic disease. The study is a Phase 3, open-label, randomized trial involving multiple centers. Participants will be randomly assigned to receive either PF-07220060 plus letrozole or the investigator's choice of one of the approved CDK4/6 inhibitors (palbociclib, ribociclib, or abemaciclib) combined with letrozole. The treatments are given as drugs with letrozole serving as endocrine therapy. The study compares these treatments in terms of how well they control the cancer and their safety profiles. Participants will visit the study clinic regularly for monitoring during treatment. Researchers will assess how long participants live without their disease worsening or dying from any cause, which is the main outcome measured up to about four years. The study team will monitor each participant's health and response to treatment through these visits to gather information about treatment effects and safety.