An Interventional, Open-label, Randomized, Multicenter Phase 3 Study of PF-07220060 plus Letrozole Compared to CDK4/6 Inhibitor Plus Letrozole in Participants over 18 Years with Hormone Receptor (HR)-Positive, HER2-Negatrive Advanced/Metastatic Breast Cancer Who Have Not Received Any Prior Systemic Anti-Cancer Treatment for Advanced/Metastatic Disease

The purpose of the study is to evaluate whether PF-07220060 plus letrozole can improve clinical outcomes relative to cyclin-dependent kinase (CDK) 4/6 inhibitor (CDK4/6i) (investigator’s choice: abemaciclib, palbociclib or ribociclib) plus letrozole in participants
with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)- negative advanced or metastatic breast cancer (a/mBC) who have not received any prior systemic anticancer treatment for advanced/metastatic disease.