A Study to Learn About the Study Medicine Called PF-07220060 in Combination With Fulvestrant in People With HR-positive, HER2-negative Advanced or Metastatic Breast Cancer Who Progressed After a Prior Line of Treatment

The purpose of this study is to learn about the safety and how effective the study medicine (PF-07220060) plus fulvestrant is compared to the study doctor's choice of treatment in people with advanced or metastatic breast cancer. Advanced cancer is the one that is unlikely to be cured or taken care of with treatment. Metastatic cancer is the one that has spread to other parts of the body.

This study is seeking female and male participants who:

• are 18 years of age or older;

• are hormone receptor (HR)-positive and human epidermal growth factor receptor 2 (HER2)-negative;

• have advanced or metastatic breast cancer after taking other treatments before this study;

• have not taken or need to take medications that are not allowed by the study protocol;

• do not have any medical or mental conditions that may increase the risk of study participation.

Half of the participants will take PF-07220060 two times daily by mouth along with fulvestrant. Fulvestrant will be given as a shot into the muscle. The other half will take the study doctor's choice of treatment which can either be:

• Fulvestrant alone taken as shot into the muscle.

• Everolimus along with exemestane taken once daily by mouth.

This study will compare the experiences of participants receiving the study medicine plus fulvestrant to those who are receiving the study doctor's choice of treatment. This will help decide if the study medicine is safe and effective.

Participants will receive study treatment and/or will be in the study until:

• imaging scans (such as an MRI and/or CT) show that their cancer is getting worse.

• the study doctor thinks the participant is no longer benefitting from the study medicine.

• has side effects that become too severe. A side effect is a reaction (expected or unexpected) to a medicine or treatment you take.

• the participant chooses to stop taking part.