This study is for adults with a specific type of breast cancer called HR-positive and HER2-negative. HR-positive means that the cancer cells grow due to hormones like estrogen or progesterone. HER2-negative means the cancer cells have a little or no amount of a protein called HER2. This study focuses on people whose cancer has spread nearby or to other parts of the body and who have not yet received treatment for their advanced condition. Participants will be divided into two groups. One group will receive a new drug called PF-07220060 with letrozole, and the other group will get a standard treatment chosen by doctors with letrozole. Doctors will regularly check on participants to see how the treatment is working.

• The study involves regular visits to the clinic for monitoring.
• Participants will either receive the new drug or a standard treatment.
• Participants must not have received any treatment for their advanced cancer.